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Pelka EZ, Davis BR, McDaniel J. Sourcebook update: using near-infrared spectroscopy to assess skeletal muscle oxygen uptake. ADVANCES IN PHYSIOLOGY EDUCATION 2024; 48:566-572. [PMID: 38779745 DOI: 10.1152/advan.00047.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Revised: 04/16/2024] [Accepted: 05/12/2024] [Indexed: 05/25/2024]
Abstract
Monitoring the metabolic cost or oxygen consumption associated with rest and exercise is crucial to understanding the impact of disease or physical training on the health of individuals. Traditionally, measuring the skeletal muscle oxygen cost associated with exercise/muscle contractions can be rather expensive or invasive (i.e., muscle biopsies). More recently, specific protocols designed around the use of near-infrared spectroscopy (NIRS) have been shown to provide a quick, noninvasive easy-to-use tool to measure skeletal muscle oxygen consumption ([Formula: see text]). However, the data and results from NIRS devices are often misunderstood. Thus the primary purpose of this sourcebook update is to provide several experimental protocols students can utilize to improve their understanding of NIRS technology, learn how to analyze results from NIRS devices, and better understand how muscle contraction intensity and type (isometric, concentric, or eccentric) influence the oxygen cost of muscle contractions.NEW & NOTEWORTHY Compared to traditional methods, near-infrared spectroscopy (NIRS) provides a relatively cheap and easy-to-use noninvasive technique to measure skeletal muscle oxygen uptake following exercise. This laboratory not only enables students to learn about the basics of NIRS and muscle energetics but also addresses more complex questions regarding skeletal muscle physiology.
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Affiliation(s)
- Edward Z Pelka
- Exercise Science and Exercise Physiology Program, Kent State University, Kent, Ohio, United States
| | - B Ryan Davis
- Exercise Science and Exercise Physiology Program, Kent State University, Kent, Ohio, United States
| | - John McDaniel
- Exercise Science and Exercise Physiology Program, Kent State University, Kent, Ohio, United States
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2
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Raiteri BJ, Lauret L, Hahn D. Residual force depression is not related to positive muscle fascicle work during submaximal voluntary dorsiflexion contractions in humans. J Physiol 2024; 602:1085-1103. [PMID: 38380985 DOI: 10.1113/jp285703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Accepted: 01/18/2024] [Indexed: 02/22/2024] Open
Abstract
Residual force depression (rFD) following active muscle shortening is assumed to correlate most strongly with muscle work, but this has not been tested during voluntary contractions in humans. Using dynamometry, we compared steady-state ankle joint torques (N = 16) following tibialis anterior (TA) muscle-tendon unit (MTU) lengthening and shortening to the time-matched torque during submaximal voluntary fixed-end dorsiflexion reference contractions (REF) at a matched MTU length and EMG amplitude. Ultrasound revealed significantly reduced (P < 0.001) TA fascicle shortening amplitudes during MTU lengthening without a preload over small and medium amplitudes, respectively, relative to REF. MTU lengthening with a preload over a large amplitude significantly (P < 0.001) increased fascicle shortening relative to REF, as well as stretch amplitudes relative to MTU lengthening without a preload (P = 0.001). Significant (P = 0.028) steady-state fascicle force enhancement relative to REF was observed following MTU lengthening, and was similar among MTU lengthening-hold conditions (3-5%). MTU shortening with and without a preload over small and large amplitudes significantly (P < 0.001) increased positive fascicle and MTU work relative to REF, but significant (P = 0.006) rFD was observed following MTU shortening with a preload (7-10%) only. rFD was linearly related to positive MTU work [rrm (47) = 0.48, P < 0.001], but not positive fascicle work [rrm (47) = 0.16, P = 0.277]. Our findings indicate that MTU lengthening without substantial fascicle stretch enhances steady-state force output, which might arise from less shortening-induced rFD. Our findings also indicate similar rFD following different amounts of positive fascicle/MTU work, which cautions against using work to predict rFD during submaximal voluntary contractions. KEY POINTS: Accurately predicting muscle force is challenging because active muscle shortening depresses force output. The residual force depression (rFD) that exists following active muscle shortening is commonly assumed to correlate strongly and positively with muscle work. We found that tibialis anterior muscle fascicle work and muscle-tendon unit work did not accurately predict rFD during submaximal voluntary dorsiflexion contractions. Fascicle shortening during fixed-end reference contractions also potentially induced rFD of 3-5%, which was similar to the rFD following muscle-tendon unit shortening without a preload. A higher number of active muscle fibres during shortening probably increased rFD, which suggests that motor unit recruitment during shortening might predict rFD.
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Affiliation(s)
- Brent James Raiteri
- Human Movement Science, Faculty of Sport Science, Ruhr University Bochum, Bochum North Rhine-Westphalia, Germany
| | - Leon Lauret
- Human Movement Science, Faculty of Sport Science, Ruhr University Bochum, Bochum North Rhine-Westphalia, Germany
| | - Daniel Hahn
- Human Movement Science, Faculty of Sport Science, Ruhr University Bochum, Bochum North Rhine-Westphalia, Germany
- School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, Queensland, Australia
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3
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Li M, Leonard TR, Han SW, Moo EK, Herzog W. Gaining new understanding of sarcomere length non-uniformities in skeletal muscles. Front Physiol 2024; 14:1242177. [PMID: 38274042 PMCID: PMC10808998 DOI: 10.3389/fphys.2023.1242177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Accepted: 12/14/2023] [Indexed: 01/27/2024] Open
Abstract
Sarcomere lengths are non-uniform on all structural levels of mammalian skeletal muscle. These non-uniformities have been associated with a variety of mechanical properties, including residual force enhancement and depression, creep, increased force capacity, and extension of the plateau of the force-length relationship. However, the nature of sarcomere length non-uniformities has not been explored systematically. The purpose of this study was to determine the properties of sarcomere length non-uniformities in active and passive muscle. Single myofibrils of rabbit psoas (n = 20; with 412 individual sarcomeres) were subjected to three activation/deactivation cycles and individual sarcomere lengths were measured at 4 passive and 3 active points during the activation/deactivation cycles. The myofibrils were divided into three groups based on their initial average sarcomere lengths: short, intermediate, and long average sarcomere lengths of 2.7, 3.2, and 3.6 µm. The primary results were that sarcomere length non-uniformities did not occur randomly but were governed by some structural and/or contractile properties of the sarcomeres and that sarcomere length non-uniformities increased when myofibrils went from the passive to the active state. We propose that the mechanisms that govern the systematic sarcomere lengths non-uniformities observed in active and passive myofibrils may be associated with the variable number of contractile proteins and the variable number and the adjustable stiffness of titin filaments in individual sarcomeres.
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Affiliation(s)
- Meng Li
- Human Performance Lab, University of Calgary, Calgary, AB, Canada
| | - T. R. Leonard
- Human Performance Lab, University of Calgary, Calgary, AB, Canada
| | - S. W. Han
- Institute of Physiology II, University of Münster, Münster, Germany
| | - E. K. Moo
- Human Performance Lab, University of Calgary, Calgary, AB, Canada
- Department of Technical Physics, University of Eastern Finland, Kuopio, Finland
- Department of Mechanical and Aerospace Engineering, Carleton University, Ottawa, ON, Canada
| | - W. Herzog
- Human Performance Lab, University of Calgary, Calgary, AB, Canada
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4
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Han SW, Boldt K, Joumaa V, Herzog W. Characterizing residual and passive force enhancements in cardiac myofibrils. Biophys J 2023; 122:1538-1547. [PMID: 36932677 PMCID: PMC10147830 DOI: 10.1016/j.bpj.2023.03.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Revised: 11/07/2022] [Accepted: 03/14/2023] [Indexed: 03/19/2023] Open
Abstract
Residual force enhancement (RFE), an increase in isometric force after active stretching of a muscle compared with the purely isometric force at the corresponding length, has been consistently observed throughout the structural hierarchy of skeletal muscle. Similar to RFE, passive force enhancement (PFE) is also observable in skeletal muscle and is defined as an increase in passive force when a muscle is deactivated after it has been actively stretched compared with the passive force following deactivation of a purely isometric contraction. These history-dependent properties have been investigated abundantly in skeletal muscle, but their presence in cardiac muscle remains unresolved and controversial. The purpose of this study was to investigate whether RFE and PFE exist in cardiac myofibrils and whether the magnitudes of RFE and PFE increase with increasing stretch magnitudes. Cardiac myofibrils were prepared from the left ventricles of New Zealand White rabbits, and the history-dependent properties were tested at three different final average sarcomere lengths (n = 8 for each), 1.8, 2, and 2.2 μm, while the stretch magnitude was kept at 0.2 μm/sarcomere. The same experiment was repeated with a final average sarcomere length of 2.2 μm and a stretching magnitude of 0.4 μm/sarcomere (n = 8). All 32 cardiac myofibrils exhibited increased forces after active stretching compared with the corresponding purely isometric reference conditions (p < 0.05). Furthermore, the magnitude of RFE was greater when myofibrils were stretched by 0.4 compared with 0.2 μm/sarcomere (p < 0.05). We conclude that, like in skeletal muscle, RFE and PFE are properties of cardiac myofibrils and are dependent on stretch magnitude.
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Affiliation(s)
- Seong-Won Han
- Institute of Physiology II, Faculty of Medicine, University of Münster, Münster, Germany; Faculty of Kinesiology, University of Calgary, Calgary, Canada.
| | - Kevin Boldt
- Faculty of Kinesiology, University of Calgary, Calgary, Canada; Kinesiology Program, Trent University, Peterborough, ON, Canada; Department of Human Health and Nutritional Science, University of Guelph, Guelph, ON, Canada
| | - Venus Joumaa
- Faculty of Kinesiology, University of Calgary, Calgary, Canada
| | - Walter Herzog
- Faculty of Kinesiology, University of Calgary, Calgary, Canada
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5
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Hahn D, Han SW, Joumaa V. The history-dependent features of muscle force production: A challenge to the cross-bridge theory and their functional implications. J Biomech 2023; 152:111579. [PMID: 37054597 DOI: 10.1016/j.jbiomech.2023.111579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2023] [Accepted: 04/03/2023] [Indexed: 04/15/2023]
Abstract
The cross-bridge theory predicts that muscle force is determined by muscle length and the velocity of active muscle length changes. However, before the formulation of the cross-bridge theory, it had been observed that the isometric force at a given muscle length is enhanced or depressed depending on active muscle length changes before that given length is reached. These enhanced and depressed force states are termed residual force enhancement (rFE) and residual force depression (rFD), respectively, and together they are known as the history-dependent features of muscle force production. In this review, we introduce early attempts in explaining rFE and rFD before we discuss more recent research from the past 25 years which has contributed to a better understanding of the mechanisms underpinning rFE and rFD. Specifically, we discuss the increasing number of findings on rFE and rFD which challenge the cross-bridge theory and propose that the elastic element titin plays a role in explaining muscle history-dependence. Accordingly, new three-filament models of force production including titin seem to provide better insight into the mechanism of muscle contraction. Complementary to the mechanisms behind muscle history-dependence, we also show various implications for muscle history-dependence on in-vivo human muscle function such as during stretch-shortening cycles. We conclude that titin function needs to be better understood if a new three-filament muscle model which includes titin, is to be established. From an applied perspective, it remains to be elucidated how muscle history-dependence affects locomotion and motor control, and whether history-dependent features can be changed by training.
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Affiliation(s)
- Daniel Hahn
- Human Movement Science, Faculty of Sport Science, Ruhr University, Bochum, Germany; School of Human Movement and Nutrition Sciences, University of Queensland, Australia
| | - Seong-Won Han
- Institute of Physiology II, Faculty of Medicine, University of Münster, Germany.
| | - Venus Joumaa
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Alberta, Canada
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Fukutani A, Hashizume S, Isaka T. Measurements of tendon length changes during stretch-shortening cycles in rat soleus. Sci Rep 2023; 13:5381. [PMID: 37009784 PMCID: PMC10068606 DOI: 10.1038/s41598-023-32370-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 03/27/2023] [Indexed: 04/04/2023] Open
Abstract
The muscle force attained during concentric contractions is augmented by a preceding eccentric contraction (the stretch-shortening cycle (SSC) effect). At present, tendon elongation is considered the primary mechanism. However, we recently found that the magnitude of the SSC effect was not different, even after removing the Achilles tendon. To resolve these discrepant results, direct measurement of changes in Achille tendon length is required. Therefore, this study aimed to elucidate the influence of tendon elongation on the SSC effect by directly measuring the changes in Achilles tendon length. The rat soleus was subjected to pure concentric contractions (pure shortening trials) and concentric contractions with a preceding eccentric contraction (SSC trials). During these contractions, the Achilles tendon length was visualized using a video camera. The muscle force attained during the concentric contraction phase in the SSC trial was significantly larger than that in the pure shortening trial (p = 0.022), indicating the existence of the SSC effect. However, the changes in Achilles tendon length were not different between trials (i.e., the magnitude of tendon shortening attained during the shortening phase was 0.20 ± 0.14 mm for the SSC trial vs. 0.17 ± 0.09 mm for the pure shortening trial), indicating that the observed SSC effect is difficult to be explained by the elastic energy stored in tendons or muscle-tendon interaction. In conclusion, the effect of tendon elongation on the SSC effect should be reconsidered, and other factors may contribute to the SSC effect.
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Affiliation(s)
- Atsuki Fukutani
- Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga, 525-8577, Japan.
| | - Satoru Hashizume
- Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga, 525-8577, Japan
| | - Tadao Isaka
- Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga, 525-8577, Japan
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Eccentric muscle contractions: from single muscle fibre to whole muscle mechanics. Pflugers Arch 2023; 475:421-435. [PMID: 36790515 PMCID: PMC10011336 DOI: 10.1007/s00424-023-02794-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 01/24/2023] [Accepted: 02/01/2023] [Indexed: 02/16/2023]
Abstract
Eccentric muscle loading encompasses several unique features compared to other types of contractions. These features include increased force, work, and performance at decreased oxygen consumption, reduced metabolic cost, improved energy efficiency, as well as decreased muscle activity. This review summarises explanatory approaches to long-standing questions in terms of muscular contraction dynamics and molecular and cellular mechanisms underlying eccentric muscle loading. Moreover, this article intends to underscore the functional link between sarcomeric components, emphasising the fundamental role of titin in skeletal muscle. The giant filament titin reveals versatile functions ranging from sarcomere organisation and maintenance, providing passive tension and elasticity, and operates as a mechanosensory and signalling platform. Structurally, titin consists of a viscoelastic spring segment that allows activation-dependent coupling to actin. This titin-actin interaction can explain linear force increases in active lengthening experiments in biological systems. A three-filament model of skeletal muscle force production (mediated by titin) is supposed to overcome significant deviations between experimental observations and predictions by the classic sliding-filament and cross-bridge theories. Taken together, this review intends to contribute to a more detailed understanding of overall muscle behaviour and force generation-from a microscopic sarcomere level to a macroscopic multi-joint muscle level-impacting muscle modelling, the understanding of muscle function, and disease.
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8
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Liu S, Baptista de Oliveira Medeiros H, de Brito Fontana H, Herzog W. Passive force enhancement is not abolished by shortening of single rabbit psoas fibres. J Biomech 2022; 145:111386. [PMID: 36410203 DOI: 10.1016/j.jbiomech.2022.111386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 10/28/2022] [Accepted: 11/09/2022] [Indexed: 11/15/2022]
Abstract
Passive force enhancement is defined as the increase in steady-state passive force following deactivation of an actively stretched muscle compared to the corresponding passive force following passive stretching of the muscle. Passive force enhancement has been associated with contributing to the residual force enhancement property, providing stability to sarcomeres, and preventing sarcomeres from over-stretching during eccentric muscle action. Despite its functional importance, the molecular mechanisms underlying passive force enhancement remain unknown. Specifically, it remains unknown how passive force enhancement develops and how it is abolished. Incidental observations on cat soleus muscles led to the speculation that passive force enhancement is abolished when the actively stretched muscle is deactivated and then passively shortened to its pre-stretched length. Here, we tested this hypothesis using skinned fibres from rabbit psoas and rejected it. Rather, we found that passive force enhancement increased following shortening of the fibres to their pre-stretched length (2.4 µm), and furthermore, that the passive force enhancement increased by 70-106% when the shortening and subsequent stretch to the original length (3.6 µm) increased in duration (200 ms, 6 s, and 14 s). These results indicate that passive force enhancement increases during a shortening-stretch cycle, and that this increase is time-dependent. We propose that this increase in passive force enhancement is caused by titin; specifically, with a refolding of titin's immunoglobulin domains that were unfolded during the active fibre stretching that produced the residual and passive force enhancement. Molecular level experiments are required to test this proposal.
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Affiliation(s)
- Shuyue Liu
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | | | | | - Walter Herzog
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.
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9
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de Campos D, Orssatto LBR, Trajano GS, Herzog W, Fontana HDB. Residual force enhancement in human skeletal muscles: A systematic review and meta-analysis. JOURNAL OF SPORT AND HEALTH SCIENCE 2022; 11:94-103. [PMID: 34062271 PMCID: PMC8847921 DOI: 10.1016/j.jshs.2021.05.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 02/21/2021] [Accepted: 03/15/2021] [Indexed: 05/05/2023]
Abstract
OBJECTIVE We reviewed and appraised the existing evidence of in vivo manifestations of residual force enhancement in human skeletal muscles and assessed, through a meta-analysis, the effect of an immediate history of eccentric contraction on the subsequent torque capacity of voluntary and electrically evoked muscle contractions. METHODS Our search was conducted from database inception to May 2020. Descriptive information was extracted from, and quality was assessed for, 45 studies. Meta-analyses and metaregressions were used to analyze residual torque enhancement and its dependence on the angular amplitude of the preceding eccentric contraction. RESULTS Procedures varied across studies with regards to muscle group tested, angular stretch amplitude, randomization of contractions, time window analyzed, and verbal command. Torque capacity in isometric (constant muscle tendon unit length and joint angle) contractions preceded by an eccentric contraction was typically greater compared to purely isometric contractions, and this effect was greater for electrically evoked muscle contractions than voluntary contractions. Residual torque enhancement differed across muscle groups for the voluntary contractions, with a significant enhancement in torque observed for the adductor pollicis, ankle dorsiflexors, ankle plantar flexors, and knee extensors, but not for the elbow and knee flexors. Meta-regressions revealed that the angular amplitude of the eccentric contraction (normalized to the respective joint's full range of motion) was not associated with the residual torque enhancement observed. CONCLUSION There is evidence of residual torque enhancement for most, but not all, muscle groups, and residual torque enhancement is greater for electrically evoked than for voluntary contractions. Contrary to our hypothesis, and contrary to generally accepted findings on isolated muscle preparations, residual torque enhancement in voluntary and electrically evoked contractions does not seem to depend on the angular amplitude of the preceding eccentric contraction.
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Affiliation(s)
- Daiani de Campos
- Biomechanics Laboratory, Federal University of Santa Catarina, Florianopolis 88040-001, Brazil
| | - Lucas B R Orssatto
- Faculty of Health, School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane QLD 4030, Australia
| | - Gabriel S Trajano
- Faculty of Health, School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane QLD 4030, Australia
| | - Walter Herzog
- Biomechanics Laboratory, Federal University of Santa Catarina, Florianopolis 88040-001, Brazil; Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, AB T2N 1N4, Canada
| | - Heiliane de Brito Fontana
- Biomechanics Laboratory, Federal University of Santa Catarina, Florianopolis 88040-001, Brazil; School of Biological Sciences, Federal University of Santa Catarina, Florianopolis 88040-900, Brazil.
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10
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Effect of Active Lengthening and Shortening on Small-Angle X-ray Reflections in Skinned Skeletal Muscle Fibres. Int J Mol Sci 2021; 22:ijms22168526. [PMID: 34445232 PMCID: PMC8395229 DOI: 10.3390/ijms22168526] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 07/30/2021] [Accepted: 08/03/2021] [Indexed: 01/04/2023] Open
Abstract
Our purpose was to use small-angle X-ray diffraction to investigate the structural changes within sarcomeres at steady-state isometric contraction following active lengthening and shortening, compared to purely isometric contractions performed at the same final lengths. We examined force, stiffness, and the 1,0 and 1,1 equatorial and M3 and M6 meridional reflections in skinned rabbit psoas bundles, at steady-state isometric contraction following active lengthening to a sarcomere length of 3.0 µm (15.4% initial bundle length at 7.7% bundle length/s), and active shortening to a sarcomere length of 2.6 µm (15.4% bundle length at 7.7% bundle length/s), and during purely isometric reference contractions at the corresponding sarcomere lengths. Compared to the reference contraction, the isometric contraction after active lengthening was associated with an increase in force (i.e., residual force enhancement) and M3 spacing, no change in stiffness and the intensity ratio I1,1/I1,0, and decreased lattice spacing and M3 intensity. Compared to the reference contraction, the isometric contraction after active shortening resulted in decreased force, stiffness, I1,1/I1,0, M3 and M6 spacings, and M3 intensity. This suggests that residual force enhancement is achieved without an increase in the proportion of attached cross-bridges, and that force depression is accompanied by a decrease in the proportion of attached cross-bridges. Furthermore, the steady-state isometric contraction following active lengthening and shortening is accompanied by an increase in cross-bridge dispersion and/or a change in the cross-bridge conformation compared to the reference contractions.
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11
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Schmidt J, Jinha A, Herzog W. Sarcomere length measurement reliability in single myofibrils. J Biomech 2021; 126:110628. [PMID: 34274869 DOI: 10.1016/j.jbiomech.2021.110628] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 06/23/2021] [Accepted: 07/05/2021] [Indexed: 11/27/2022]
Abstract
Sarcomere length non-uniformities occur at all structural levels of skeletal muscles and have been associated with important mechanical properties. Changes in sarcomere length non-uniformities in the nano- and sub-nanometer range have been used to explain muscle properties and contractile mechanisms. Typically, these measurements rely on light microscopy with a limited spatial resolution. One critical aspect in sarcomere length determination is the relatively arbitrary choice of intensity thresholds used to delineate sarcomere structures, such as A-bands or Z-lines. In experiments, these structures are typically distorted, intensity profiles vary, and baselines drift, resulting in asymmetric intensity patterns, causing changes in the centroid location of these structures depending on threshold choice, resulting in changes of sarcomere lengths. The purpose of this study was to determine the changes in (half-) sarcomere lengths associated with small changes in the A-band threshold choice. Sarcomere and half-sarcomere length changes for minute variations in A-band threshold were 28 nm (±28 nm) and 18 nm (±22 nm), respectively, and for the entire feasible range of thresholds across A-bands were 123 nm (±88 nm) and 99 nm (±105 nm), respectively. We conclude from these results that (half-) sarcomere lengths in the nanometer range obtained with light microcopy are noise, and the functional implications associated with such data should be discarded. We suggest that a functional resolution for sarcomere length of 100 nm (0.1 µm) is reasonable and 50 nm (0.05 µm) might be possible under ideal conditions.
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Affiliation(s)
- Jonas Schmidt
- University of Calgary, Faculty of Kinesiology, Human Performance Lab, Canada; Department of Biomimetics, Hochschule Bremen City University of Applied Sciences, Bremen, Germany; Faculty of Production Engineering, University of Bremen, Bremen, Germany
| | - Azim Jinha
- University of Calgary, Faculty of Kinesiology, Human Performance Lab, Canada
| | - Walter Herzog
- University of Calgary, Faculty of Kinesiology, Human Performance Lab, Canada; School of Sports, Federal University of Santa Catarina, Florianopolis, SC, Brazil.
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12
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Joumaa V, Fukutani A, Herzog W. Energy Cost of Force Production After a Stretch-Shortening Cycle in Skinned Muscle Fibers: Does Muscle Efficiency Increase? Front Physiol 2021; 11:567538. [PMID: 33536930 PMCID: PMC7848195 DOI: 10.3389/fphys.2020.567538] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 12/23/2020] [Indexed: 12/26/2022] Open
Abstract
Muscle force is enhanced during shortening when shortening is preceded by an active stretch. This phenomenon is known as the stretch-shortening cycle (SSC) effect. For some stretch-shortening conditions this increase in force during shortening is maintained following SSCs when compared to the force following a pure shortening contraction. It has been suggested that the residual force enhancement property of muscles, which comes into play during the stretch phase of SSCs may contribute to the force increase after SSCs. Knowing that residual force enhancement is associated with a substantial reduction in metabolic energy per unit of force, it seems reasonable to assume that the metabolic energy cost per unit of force is also reduced following a SSC. The purpose of this study was to determine the energy cost per unit of force at steady-state following SSCs and compare it to the corresponding energy cost following pure shortening contractions of identical speed and magnitude. We hypothesized that the energy cost per unit of muscle force is reduced following SSCs compared to the pure shortening contractions. For the SSC tests, rabbit psoas fibers (n = 12) were set at an average sarcomere length (SL) of 2.4 μm, activated, actively stretched to a SL of 3.2 μm, and shortened to a SL of 2.6 or 3.0 μm. For the pure shortening contractions, the same fibers were activated at a SL of 3.2 μm and actively shortened to a SL of 2.6 or 3.0 μm. The amount of ATP consumed was measured over a 40 s steady-state total isometric force following either the SSCs or the pure active shortening contractions. Fiber stiffness was determined in an additional set of 12 fibers, at steady-state for both experimental conditions. Total force, ATP consumption, and stiffness were greater following SSCs compared to the pure shortening contractions, but ATP consumption per unit of force was the same between conditions. These results suggest that the increase in total force observed following SSCs was achieved with an increase in the proportion of attached cross-bridges and titin stiffness. We conclude that muscle efficiency is not enhanced at steady-state following SSCs.
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Affiliation(s)
- Venus Joumaa
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
| | - Atsuki Fukutani
- Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Japan
| | - Walter Herzog
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.,Biomechanics Laboratory, School of Sports, Federal University of Santa Catarina, Florianopolis, Brazil
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13
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Fukutani A, Isaka T, Herzog W. Evidence for Muscle Cell-Based Mechanisms of Enhanced Performance in Stretch-Shortening Cycle in Skeletal Muscle. Front Physiol 2021; 11:609553. [PMID: 33488399 PMCID: PMC7820781 DOI: 10.3389/fphys.2020.609553] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 11/30/2020] [Indexed: 12/30/2022] Open
Abstract
Force attained during concentric contraction (active shortening) is transiently enhanced following eccentric contraction (active stretch) in skeletal muscle. This phenomenon is called stretch-shortening cycle (SSC) effect. Since many human movements contain combinations of eccentric and concentric contractions, a better understanding of the mechanisms underlying the SSC effect would be useful for improving physical performance, optimizing human movement efficiency, and providing an understanding of fundamental mechanism of muscle force control. Currently, the most common mechanisms proposed for the SSC effect are (i) stretch-reflex activation and (ii) storage of energy in tendons. However, abundant SSC effects have been observed in single fiber preparations where stretch-reflex activation is eliminated and storage of energy in tendons is minimal at best. Therefore, it seems prudent to hypothesize that factor(s) other than stretch-reflex activation and energy storage in tendons contribute to the SSC effect. In this brief review, we focus on possible candidate mechanisms for the SSC effect, that is, pre-activation, cross-bridge kinetics, and residual force enhancement (RFE) obtained in experimental preparations that exclude/control the influence of stretch-reflex activation and energy storage in tendons. Recent evidence supports the contribution of these factors to the mechanism of SSCs, and suggests that the extent of their contribution varies depending on the contractile conditions. Evidence for and against alternative mechanisms are introduced and discussed, and unresolved problems are mentioned for inspiring future studies in this field of research.
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Affiliation(s)
- Atsuki Fukutani
- Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Japan
- Department of Physiology and Pharmacology, Karolinska Institutet, Solna, Sweden
| | - Tadao Isaka
- Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Japan
| | - Walter Herzog
- Faculty of Kinesiology, The University of Calgary, Calgary, AB, Canada
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14
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Mahmood S, Sawatsky A, Herzog W. Increased force following muscle stretching and simultaneous fibre shortening: Residual force enhancement or force depression - That is the question? J Biomech 2021; 116:110216. [PMID: 33460865 DOI: 10.1016/j.jbiomech.2020.110216] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 10/29/2020] [Accepted: 12/25/2020] [Indexed: 11/25/2022]
Abstract
Residual force enhancement (rFE) describes the increase in isometric force following muscle stretching compared to the corresponding isometric force. Even though rFE is consistently observed in isolated muscle preparations, it is not always observed in human skeletal muscle. This inconsistency might be associated with disociations between length changes in muscle tendon units (MTUs) and fibres. This prompted the question if there is rFE for conditions where the MTU is stretched while fibres shorten. Rabbit tibialis anterior (TA) MTUs (n = 4) were stretched and the isometric forces following stretching were compared to corresponding forces from isometric reference contractions. Unique combinations of stretch speed and activation were used to create conditions of continuous fibre shortening during MTU stretch. Mean force was increased (18 ± 2%) following MTU stretching compared to the isometric reference forces. Without fibre length measurements, this result would be referred to as rFE. However, fibre shortening in the reference contractions was always greater than for the eccentric stretch contractions, suggesting that the observed increase in force might be caused by less residual force depression (rFD) in the stretch tests compared to the reference contractions. However, the work performed by fibre shortening was similar between the reference and the MTU stretch contractions, suggesting that rFD was similar for both experimental conditions. Therefore, we conclude that we observed rFE in the absence of contractile element stretching. However, a lack of knowledge of the molecular mechanisms that distinguish rFE from rFD prevents an unequivocal pronouncement of what caused the enhanced forces after active muscle stretching.
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Affiliation(s)
- Sheharzad Mahmood
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Andrew Sawatsky
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Walter Herzog
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada; Biomechanics Laboratory, School of Sports, Federal University of Santa Catarina, Florianopolis, SC, Brazil.
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15
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Haeger R, de Souza Leite F, Rassier DE. Sarcomere length non-uniformities dictate force production along the descending limb of the force-length relation. Proc Biol Sci 2020; 287:20202133. [PMID: 33109011 DOI: 10.1098/rspb.2020.2133] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The force-length relation is one of the most defining features of muscle contraction, and yet a topic of debate in the literature. The sliding filament theory predicts that the force produced by muscle fibres is proportional to the degree of overlap between myosin and actin filaments, producing a linear descending limb of the active force-length relation. However, several studies have shown forces that are larger than predicted, especially at long sarcomere lengths (SLs). Studies have been conducted with muscle fibres, preparations containing thousands of sarcomeres that make measurements of individual SL challenging. The aim of this study was to evaluate force production and sarcomere dynamics in isolated myofibrils and single sarcomeres from the rabbit psoas muscle to enhance our understanding of the theoretically predicted force-length relation. Contractions at varying SLs along the plateau (SL = 2.25-2.39 µm) and the descending limb (SL > 2.39 µm) of the force-length relation were induced in sarcomeres and myofibrils, and different modes of force measurements were used. Our results show that when forces are measured in single sarcomeres, the experimental force-length relation follows theoretical predictions. When forces are measured in myofibrils with large SL dispersions, there is an extension of the plateau and forces elevated above the predicted levels along the descending limb. We also found an increase in SL non-uniformity and slowed rates of force production at long lengths in myofibrils but not in single sarcomere preparations. We conclude that the deviation of the descending limb of the force-length relation is correlated with the degree of SL non-uniformity and slowed force development.
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Affiliation(s)
- Ricarda Haeger
- Kinesiology and Physical Education, McGill University, Montreal, QC, Canada
| | | | - Dilson E Rassier
- Kinesiology and Physical Education, McGill University, Montreal, QC, Canada
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16
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Boldt K, Han SW, Joumaa V, Herzog W. Residual and passive force enhancement in skinned cardiac fibre bundles. J Biomech 2020; 109:109953. [PMID: 32807325 DOI: 10.1016/j.jbiomech.2020.109953] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 07/06/2020] [Accepted: 07/08/2020] [Indexed: 11/28/2022]
Abstract
In skeletal muscle, steady-state force is consistently greater following active stretch than during a purely isometric contraction at the same length (residual force enhancement; RFE). Similarly, when deactivated, the force remains higher following active stretch than following an isometric condition (passive force enhancement; PFE). RFE and PFE have been associated with the sarcomere protein titin, but skeletal and cardiac titin have different structures, and results regarding RFE in cardiac muscle have been inconsistent and contradictory. Therefore, the purpose of this study was to determine if cardiac muscle exhibits RFE and PFE. Skinned fibre bundles (n = 10) were activated isometrically at a sarcomere length of 2.2 μm and actively stretched by 15% of their length. The resultant active and passive forces were compared to the corresponding forces obtained for purely isometric contractions at the long length. RFE was observed in all fibre bundles, averaging 5.5 ± 2.5% (ranging from 2.3 to 9.4%). PFE was observed in nine of the ten bundles, averaging 11.1 ± 6.5% (ranging from -2.1 to 18.7%). Stiffness was not different between the active isometric and the force enhanced conditions, but was higher following deactivation from the force-enhanced compared to the isometric reference state. We conclude that there is RFE and PFE in cardiac muscle. We speculate that cardiac muscle has the same RFE capability as skeletal muscle, and that the most likely mechanism for the RFE and PFE is the engagement of a passive structural element during active stretching.
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Affiliation(s)
- Kevin Boldt
- Faculty of Kinesiology, Human Performance Laboratory, University of Calgary, Canada.
| | - Seong-Won Han
- Faculty of Kinesiology, Human Performance Laboratory, University of Calgary, Canada
| | - Venus Joumaa
- Faculty of Kinesiology, Human Performance Laboratory, University of Calgary, Canada
| | - Walter Herzog
- Faculty of Kinesiology, Human Performance Laboratory, University of Calgary, Canada
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17
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Chen J, Mashouri P, Fontyn S, Valvano M, Elliott-Mohamed S, Noonan AM, Brown SHM, Power GA. The influence of training-induced sarcomerogenesis on the history dependence of force. J Exp Biol 2020; 223:jeb218776. [PMID: 32561632 DOI: 10.1242/jeb.218776] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Accepted: 06/09/2020] [Indexed: 12/21/2022]
Abstract
The increase or decrease in isometric force following active muscle lengthening or shortening, relative to a reference isometric contraction at the same muscle length and level of activation, are referred to as residual force enhancement (rFE) and residual force depression (rFD), respectively. The purpose of these experiments was to investigate the trainability of rFE and rFD on the basis of serial sarcomere number (SSN) alterations to history-dependent force properties. Maximal rFE/rFD measures from the soleus and extensor digitorum longus (EDL) of rats were compared after 4 weeks of uphill or downhill running with a no-running control. SSN adapted to the training: soleus SSN was greater with downhill compared with uphill running, while EDL demonstrated a trend towards more SSN for downhill compared with no running. In contrast, rFE and rFD did not differ across training groups for either muscle. As such, it appears that training-induced SSN adaptations do not modify rFE or rFD at the whole-muscle level.
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Affiliation(s)
- Jackey Chen
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Parastoo Mashouri
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Stephanie Fontyn
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Mikella Valvano
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Shakeap Elliott-Mohamed
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Alex M Noonan
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Stephen H M Brown
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Geoffrey A Power
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
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18
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Tomalka A, Weidner S, Hahn D, Seiberl W, Siebert T. Cross-Bridges and Sarcomeric Non-cross-bridge Structures Contribute to Increased Work in Stretch-Shortening Cycles. Front Physiol 2020; 11:921. [PMID: 32848862 PMCID: PMC7399218 DOI: 10.3389/fphys.2020.00921] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 07/09/2020] [Indexed: 11/13/2022] Open
Abstract
Stretch-shortening cycles (SSCs) refer to the muscle action when an active muscle stretch is immediately followed by active muscle shortening. This combination of eccentric and concentric contractions is the most important type of daily muscle action and plays a significant role in natural locomotion such as walking, running or jumping. SSCs are used in human and animal movements especially when a high movement speed or economy is required. A key feature of SSCs is the increase in muscular force and work during the concentric phase of a SSC by more than 50% compared with concentric muscle actions without prior stretch (SSC-effect). This improved muscle capability is related to various mechanisms, including pre-activation, stretch-reflex responses and elastic recoil from serial elastic tissues. Moreover, it is assumed that a significant contribution to enhanced muscle capability lies in the sarcomeres itself. Thus, we investigated the force output and work produced by single skinned fibers of rat soleus muscles during and after ramp contractions at a constant velocity. Shortening, lengthening, and SSCs were performed under physiological boundary conditions with 85% of the maximum shortening velocity and stretch-shortening magnitudes of 18% of the optimum muscle length. The different contributions of cross-bridge (XB) and non-cross-bridge (non-XB) structures to the total muscle force were identified by using Blebbistatin. The experiments revealed three main results: (i) partial detachment of XBs during the eccentric phase of a SSC, (ii) significantly enhanced forces and mechanical work during the concentric phase of SSCs compared with shortening contractions with and without XB-inhibition, and (iii) no residual force depression after SSCs. The results obtained by administering Blebbistatin propose a titin-actin interaction that depends on XB-binding or active XB-based force production. The findings of this study further suggest that enhanced forces generated during the active lengthening phase of SSCs persist during the subsequent shortening phase, thereby contributing to enhanced work. Accordingly, our data support the hypothesis that sarcomeric mechanisms related to residual force enhancement also contribute to the SSC-effect. The preload of the titin molecule, acting as molecular spring, might be part of that mechanism by increasing the mechanical efficiency of work during physiological SSCs.
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Affiliation(s)
- André Tomalka
- Department of Motion and Exercise Science, University of Stuttgart, Stuttgart, Germany
| | - Sven Weidner
- Department of Motion and Exercise Science, University of Stuttgart, Stuttgart, Germany
| | - Daniel Hahn
- Human Movement Science, Faculty of Sports Science, Ruhr University Bochum, Bochum, Germany.,School of Human Movement and Nutrition Sciences, University of Queensland, Brisbane, QLD, Australia
| | - Wolfgang Seiberl
- Human Movement Science, Bundeswehr University Munich, Munich, Germany
| | - Tobias Siebert
- Department of Motion and Exercise Science, University of Stuttgart, Stuttgart, Germany
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19
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Moo EK, Herzog W. Sarcomere Lengths Become More Uniform Over Time in Intact Muscle-Tendon Unit During Isometric Contractions. Front Physiol 2020; 11:448. [PMID: 32477162 PMCID: PMC7235410 DOI: 10.3389/fphys.2020.00448] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 04/09/2020] [Indexed: 12/12/2022] Open
Abstract
The seemingly uniform striation pattern of skeletal muscles, quantified in terms of sarcomere lengths (SLs), is inherently non-uniform across all hierarchical levels. The SL non-uniformity theory has been used to explain the force creep in isometric contractions, force depression following shortening of activated muscle, and residual force enhancement following lengthening of activated muscle. Our understanding of sarcomere contraction dynamics has been derived primarily from in vitro experiments using regular bright-field light microscopy or laser diffraction techniques to measure striation/diffraction patterns in isolated muscle fibers or myofibrils. However, the collagenous extracellular matrices present around the muscle fibers, as well as the complex architecture in the whole muscles may lead to different contraction dynamics of sarcomeres than seen in the in vitro studies. Here, we used multi-photon excitation microscopy to visualize in situ individual sarcomeres in intact muscle tendon units (MTUs) of mouse tibialis anterior (TA), and quantified the temporal changes of SL distribution as a function of SLs in relaxed and maximally activated muscles for quasi-steady state, fixed-end isometric conditions. The corresponding muscle forces were simultaneously measured using a force transducer. We found that SL non-uniformity, quantified by the coefficient of variation (CV) of SLs, decreased at a rate of 1.9–3.1%/s in the activated muscles, but remained constant in the relaxed muscles. The force loss during the quasi-steady state likely did not play a role in the decrease of SL non-uniformity, as similar force losses were found in the activated and relaxed muscles, but the CV of SLs in the relaxed muscles underwent negligible change over time. We conclude that sarcomeres in the mid-belly of maximally contracting whole muscles constantly re-organize their lengths into a more uniform pattern over time. The molecular mechanisms accounting for SL non-uniformity appear to differ in active and passive muscles, and need further elucidation, as do the functional implications of the SL non-uniformity.
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Affiliation(s)
- Eng Kuan Moo
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
| | - Walter Herzog
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
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20
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Abstract
Muscle has conventionally been viewed as a motor that converts chemical to kinetic energy in series with a passive spring, but new insights emerge when muscle is viewed as a composite material whose elastic elements are tuned by activation. New evidence demonstrates that calcium-dependent binding of N2A titin to actin increases titin stiffness in active skeletal muscles, which explains many long-standing enigmas of muscle physiology.
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Affiliation(s)
- Kiisa Nishikawa
- Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona
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21
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Jakobi JM, Kuzyk SL, McNeil CJ, Dalton BH, Power GA. Motor unit contributions to activation reduction and torque steadiness following active lengthening: a study of residual torque enhancement. J Neurophysiol 2020; 123:2209-2216. [PMID: 32347154 DOI: 10.1152/jn.00394.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Following active lengthening, steady-state isometric (ISO) torque is greater than a purely ISO contraction at the same muscle length, this is referred to as residual torque enhancement (rTE). A phenomenon of rTE is activation reduction, characterized by reduced electromyography (EMG) amplitude for a given torque output. We hypothesized that lower motor unit discharge rates would contribute to activation reduction and lessening torque steadiness. Ten young male subjects performed ISO dorsiflexion contractions at 10 and 20% of maximal voluntary contraction (MVC) torque. During rTE trials, the muscle was activated at 10° of plantar flexion, then the ankle was rotated to the ISO position at 40°. Fine wire electrodes recorded motor unit (MU)-discharge rates and variability from the tibialis anterior. Surface EMG quantified activation reduction, and steadiness was determined as the coefficient of variation of torque. The activation reduction was 44 and 24% at 10 and 20% MVC, respectively (P < 0.05). Fewer MUs were recorded in the rTE than ISO condition at 10% (~47%) and 20% (~36%) MVC (P < 0.05). Discharge rates were 19 and 26% lower in the rTE compared with the ISO condition for 10 and 20% MVC, respectively (P < 0.05), with no difference in variability between conditions (P > 0.05). Steadiness was ~22 and 18% lower for the rTE than ISO condition at 10 and 20% MVC (P < 0.05). Our findings indicate that activation reduction may be attributed to lower MU discharge rate and fewer detectable MUs and that this theoretically contributes to a reduction in steadiness in the rTE condition.NEW & NOTEWORTHY Our findings indicate that lower electromyographic activity during the torque enhanced condition following active lengthening compared with a purely isometric contraction arises from fewer active motor units and a lower discharge rate of those that are active. We used an acute condition of increased torque capacity to induce a decrease in net output of the motor neuron pool during a submaximal task to demonstrate, in humans, the impact of motor unit activity on torque steadiness.
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Affiliation(s)
- Jennifer M Jakobi
- School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia, Okanagan, British Columbia, Canada
| | - Samantha L Kuzyk
- School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia, Okanagan, British Columbia, Canada
| | - Chris J McNeil
- School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia, Okanagan, British Columbia, Canada
| | - Brian H Dalton
- School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia, Okanagan, British Columbia, Canada
| | - Geoffrey A Power
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, Ontario, Canada
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22
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Moo EK, Leonard TR, Herzog W. The sarcomere force-length relationship in an intact muscle-tendon unit. J Exp Biol 2020; 223:jeb215020. [PMID: 32098882 DOI: 10.1242/jeb.215020] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Accepted: 02/18/2020] [Indexed: 08/26/2023]
Abstract
The periodic striation pattern in skeletal muscle reflects the length of the basic contractile unit: the sarcomere. More than half a century ago, Gordon, Huxley and Julian provided strong support for the 'sliding filament' theory through experiments with single muscle fibres. The sarcomere force-length (FL) relationship has since been extrapolated to whole muscles in an attempt to unravel in vivo muscle function. However, these extrapolations were frequently associated with non-trivial assumptions, such as muscle length changes corresponding linearly to SL changes. Here, we determined the in situ sarcomere FL relationship in a whole muscle preparation by simultaneously measuring muscle force and individual SLs in an intact muscle-tendon unit (MTU) using state-of-the-art multi-photon excitation microscopy. We found that despite great SL non-uniformity, the mean value of SLs measured from a minute volume of the mid-belly, equivalent to about 5×10-6% of the total muscle volume, agrees well with the theoretically predicted FL relationship, but only if the precise contractile filament lengths are known, and if passive forces from parallel elastic components and activation-associated sarcomere shortening are considered properly. As SLs are not uniformly distributed across the whole muscle and changes in SL with muscle length are location dependent, our results may not be valid for the proximal or distal parts of the muscle. The approach described here, and our findings, may encourage future studies to determine the role of SL non-uniformity in influencing sarcomere FL properties in different muscles and for different locations within single muscles.
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Affiliation(s)
- Eng Kuan Moo
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada T2N 1N4
| | - Timothy R Leonard
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada T2N 1N4
| | - Walter Herzog
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada T2N 1N4
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23
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Tahir U, Monroy JA, Rice NA, Nishikawa KC. Effects of a titin mutation on force enhancement and force depression in mouse soleus muscles. ACTA ACUST UNITED AC 2020; 223:jeb.197038. [PMID: 31862847 DOI: 10.1242/jeb.197038] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2019] [Accepted: 12/19/2019] [Indexed: 01/20/2023]
Abstract
The active isometric force produced by muscles varies with muscle length in accordance with the force-length relationship. Compared with isometric contractions at the same final length, force increases after active lengthening (force enhancement) and decreases after active shortening (force depression). In addition to cross-bridges, titin has been suggested to contribute to force enhancement and depression. Although titin is too compliant in passive muscles to contribute to active tension at short sarcomere lengths on the ascending limb and plateau of the force-length relationship, recent evidence suggests that activation increases titin stiffness. To test the hypothesis that titin plays a role in force enhancement and depression, we investigated isovelocity stretching and shortening in active and passive wild-type and mdm (muscular dystrophy with myositis) soleus muscles. Skeletal muscles from mdm mice have a small deletion in the N2A region of titin and show no increase in titin stiffness during active stretch. We found that: (1) force enhancement and depression were reduced in mdm soleus compared with wild-type muscles relative to passive force after stretch or shortening to the same final length; (2) force enhancement and force depression increased with amplitude of stretch across all activation levels in wild-type muscles; and (3) maximum shortening velocity of wild-type and mdm muscles estimated from isovelocity experiments was similar, although active stress was reduced in mdm compared with wild-type muscles. The results of this study suggest a role for titin in force enhancement and depression, which contribute importantly to muscle force during natural movements.
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Affiliation(s)
- Uzma Tahir
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011-5640, USA
| | - Jenna A Monroy
- W. M. Keck Science Department, The Claremont Colleges, Claremont, CA 91711-5916, USA
| | - Nicole A Rice
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011-5640, USA
| | - Kiisa C Nishikawa
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011-5640, USA
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Fukutani A, Shimoho K, Isaka T. Pre-activation affects the effect of stretch-shortening cycle by modulating fascicle behavior. Biol Open 2019; 8:8/12/bio044651. [PMID: 31862776 PMCID: PMC6955218 DOI: 10.1242/bio.044651] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The torque attained during active shortening is enhanced after an active stretch (stretch-shortening cycle, SSC). This study examined the influence of pre-activation on fascicle behavior and the SSC effect. Subjects exhibited the following three conditions by electrically induced plantar flexions. In the isometric-concentric (ISO-CON) condition, subjects exhibited active shortening from dorsiflexion of 15° to 0° after isometric pre-activation. In the eccentric-concentric (ECC-CON) condition, subjects exhibited the above active shortening immediately after the eccentric pre-activation. In the isometric-eccentric-concentric (ISO-ECC-CON) condition, isometric pre-activation was conducted before exhibiting the ECC-CON maneuver. Joint torque and fascicle length of the medial gastrocnemius were compared. The joint torque at the onset and end of shortening was larger in the ISO-ECC-CON than in the ISO-CON or ECC-CON conditions, while no differences were found between ISO-CON and ECC-CON conditions. The magnitude of fascicle elongation attained during the active stretch was larger in the ISO-ECC-CON than in the ECC-CON condition. This could be caused by the shorter fascicle length at the onset of active stretch due to isometric pre-activation. This shorter fascicle length could lead to larger fascicle elongation during the subsequent active stretch, which should emphasize the effect of active stretch-induced force enhancement mechanism. Summary: Due to the larger fascicle elongation induced by a pre-activation, the effect of the stretch-shortening cycle is enhanced.
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Affiliation(s)
- Atsuki Fukutani
- Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577, Japan
| | - Kento Shimoho
- Graduate School of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577, Japan
| | - Tadao Isaka
- Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577, Japan
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25
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Influence of muscle length on the stretch-shortening cycle in skinned rabbit soleus. Sci Rep 2019; 9:18350. [PMID: 31797995 PMCID: PMC6892932 DOI: 10.1038/s41598-019-54959-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 11/18/2019] [Indexed: 11/21/2022] Open
Abstract
Muscle force generated during shortening is instantaneously increased after active stretch. This phenomenon is called as stretch-shortening cycle (SSC) effect. It has been suggested that residual force enhancement contributes to the SSC effect. If so, the magnitude of SSC effect should be larger in the longer muscle length condition, because the residual force enhancement is prominent in the long muscle length condition. This hypothesis was examined by performing the SSC in the short and long muscle length conditions. Skinned fibers obtained from rabbit soleus (N = 20) were used in this study. To calculate the magnitude of SSC effect, the SSC trial (isometric-eccentric-concentric-isometric) and the control trial (isometric-concentric-isometric) were conducted in the short (within the range of 2.4 to 2.7 μm) and long muscle (within the range of 3.0 to 3.3 μm). The magnitude of SSC effect was calculated as the relative increase in the mechanical work attained during the shortening phase between control and SSC trials. As a result, the magnitude of SSC effect was significantly larger in the long (176.8 ± 18.1%) than in the short muscle length condition (157.4 ± 8.5%) (p < 0.001). This result supports our hypothesis that the magnitude of SSC effect is larger in the longer muscle length condition, possibly due to the larger magnitude of residual force enhancement.
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Fukutani A, Herzog W. Current Understanding of Residual Force Enhancement: Cross-Bridge Component and Non-Cross-Bridge Component. Int J Mol Sci 2019; 20:ijms20215479. [PMID: 31689920 PMCID: PMC6862632 DOI: 10.3390/ijms20215479] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Revised: 10/31/2019] [Accepted: 11/01/2019] [Indexed: 02/06/2023] Open
Abstract
Muscle contraction is initiated by the interaction between actin and myosin filaments. The sliding of actin filaments relative to myosin filaments is produced by cross-bridge cycling, which is governed by the theoretical framework of the cross-bridge theory. The cross-bridge theory explains well a number of mechanical responses, such as isometric and concentric contractions. However, some experimental observations cannot be explained with the cross-bridge theory; for example, the increased isometric force after eccentric contractions. The steady-state, isometric force after an eccentric contraction is greater than that attained in a purely isometric contraction at the same muscle length and same activation level. This well-acknowledged and universally observed property is referred to as residual force enhancement (rFE). Since rFE cannot be explained by the cross-bridge theory, alternative mechanisms for explaining this force response have been proposed. In this review, we introduce the basic concepts of sarcomere length non-uniformity and titin elasticity, which are the primary candidates that have been used for explaining rFE, and discuss unresolved problems regarding these mechanisms, and how to proceed with future experiments in this exciting area of research.
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Affiliation(s)
- Atsuki Fukutani
- Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577, Japan.
| | - Walter Herzog
- Faculty of Kinesiology, The University of Calgary, 2500 University Drive, NW, Calgary, AB T2N 1N4, Canada.
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Blazevich AJ, Babault N. Post-activation Potentiation Versus Post-activation Performance Enhancement in Humans: Historical Perspective, Underlying Mechanisms, and Current Issues. Front Physiol 2019; 10:1359. [PMID: 31736781 PMCID: PMC6838751 DOI: 10.3389/fphys.2019.01359] [Citation(s) in RCA: 217] [Impact Index Per Article: 43.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 10/14/2019] [Indexed: 12/31/2022] Open
Abstract
Post-activation potentiation (PAP) is a well-described phenomenon with a short half-life (~28 s) that enhances muscle force production at submaximal levels of calcium saturation (i.e., submaximal levels of muscle activation). It has been largely explained by an increased myosin light chain phosphorylation occurring in type II muscle fibers, and its effects have been quantified in humans by measuring muscle twitch force responses to a bout of muscular activity. However, enhancements in (sometimes maximal) voluntary force production detected several minutes after high-intensity muscle contractions are also observed, which are also most prominent in muscles with a high proportion of type II fibers. This effect has been considered to reflect PAP. Nonetheless, the time course of myosin light chain phosphorylation (underpinning “classic” PAP) rarely matches that of voluntary force enhancement and, unlike PAP, changes in muscle temperature, muscle/cellular water content, and muscle activation may at least partly underpin voluntary force enhancement; this enhancement has thus recently been called post-activation performance enhancement (PAPE) to distinguish it from “classical” PAP. In fact, since PAPE is often undetectable at time points where PAP is maximal (or substantial), some researchers have questioned whether PAP contributes to PAPE under most conditions in vivo in humans. Equally, minimal evidence has been presented that PAP is of significant practical importance in cases where multiple physiological processes have already been upregulated by a preceding, comprehensive, active muscle warm-up. Given that confusion exists with respect to the mechanisms leading to acute enhancement of both electrically evoked (twitch force; PAP) and voluntary (PAPE) muscle function in humans after acute muscle activity, the first purpose of the present narrative review is to recount the history of PAP/PAPE research to locate definitions and determine whether they are the same phenomena. To further investigate the possibility of these phenomena being distinct as well as to better understand their potential functional benefits, possible mechanisms underpinning their effects will be examined in detail. Finally, research design issues will be addressed which might contribute to confusion relating to PAP/PAPE effects, before the contexts in which these phenomena may (or may not) benefit voluntary muscle function are considered.
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Affiliation(s)
- Anthony J Blazevich
- School of Medical and Health Science, Centre for Exercise and Sports Science Research (CESSR), Edith Cowan University, Joondalup, WA, Australia
| | - Nicolas Babault
- Faculty of Sport Sciences, French National Institute of Health and Medical Research (INSERM), Unit 1093 Cognition, Action and Sensorimotor Plasticity, Centre for Performance Expertise, University of Burgundy and Franche-Comté, Dijon, France
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Sleboda DA, Wold ES, Roberts TJ. Passive muscle tension increases in proportion to intramuscular fluid volume. ACTA ACUST UNITED AC 2019; 222:jeb.209668. [PMID: 31558592 DOI: 10.1242/jeb.209668] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Accepted: 09/22/2019] [Indexed: 12/15/2022]
Abstract
During extended bouts of exercise, muscle can increase in volume by as much as 20% as vascular fluid moves into the tissue. Recent findings suggest that the fluid content of muscle can influence the mechanics of force production; however, the extent to which natural volume fluctuations should be expected to influence muscle mechanics in vivo remains unclear. Here, using osmotic perturbations of bullfrog muscle, we explored the impacts of physiologically relevant volume fluctuations on a fundamental property of muscle: passive force production. We found that passive force and fluid volume were correlated over a 20% increase in muscle volume, with small changes in volume having significant effects on force (e.g. a 5% volume increase results in a >10% passive force increase). A simple physical model of muscle morphology reproduces these effects. These findings suggest that physiologically relevant fluid fluxes could alter passive muscle mechanics in vivo and affect organismal performance.
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Affiliation(s)
- David A Sleboda
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
| | - Ethan S Wold
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
| | - Thomas J Roberts
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
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Fortuna R, Goecking T, Seiberl W, Herzog W. Force depression following a stretch-shortening cycle depends on the amount of residual force enhancement established in the initial stretch phase. Physiol Rep 2019; 7:e14188. [PMID: 31420953 PMCID: PMC6697760 DOI: 10.14814/phy2.14188] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 06/28/2019] [Accepted: 07/05/2019] [Indexed: 11/24/2022] Open
Abstract
Studies on residual force enhancement (rFE) and residual force depression (rFD) of the muscle-tendon unit (MTU) have typically been conducted independent of each other, with little information available on how stretch-induced rFE affects the shortening phase and the steady-state MTU isometric force at the end of stretch-shortening cycles (SSCs). We showed previously that when rFE is kept constant, but the force at the end of the stretch is varied by changing the stretch speed, the steady-state forces at the end of SSCs were the same. These results led to the hypothesis that the amount of rFE of the MTU established in the initial stretch phase of SSCs determines the steady-state force following the shortening phase of SSCs. This study was aimed at testing this hypothesis. Steady-state MTU isometric thumb adduction forces were measured for pure isometric contractions, following pure shortening contractions, following pure stretch contractions, and following SSCs with constant shortening speed and magnitude. However, two stretch magnitudes (30° and 10° thumb abduction) and stretch speeds (15°/sec and ~ 60°/sec, respectively) were chosen such that forces at the end of the stretch phase of the SSCs were the same, while rFE differed substantially. As hypothesized, the steady-state isometric MTU forces following SSCs were positively related to the stretch-magnitude dependent amount of rFE established in the stretch phase and were independent of the force reached at the end of the stretch phase in SSCs. Among many competing theories, these results can potentially be explained with the idea that there is a length-specific engagement of a passive structural element at the initial length of muscle activation.
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Affiliation(s)
- Rafael Fortuna
- Human Performance Laboratory, Faculty of KinesiologyUniversity of CalgaryCalgaryCanada
| | - Tobias Goecking
- Department of Biomechanics in Sports, Faculty of Sport and Health SciencesTechnical University of MunichMunichGermany
- Institute of Sport Science, Department of Human SciencesBundeswehr University MunichMunichGermany
| | - Wolfgang Seiberl
- Human Performance Laboratory, Faculty of KinesiologyUniversity of CalgaryCalgaryCanada
- Department of Biomechanics in Sports, Faculty of Sport and Health SciencesTechnical University of MunichMunichGermany
- Institute of Sport Science, Department of Human SciencesBundeswehr University MunichMunichGermany
| | - Walter Herzog
- Human Performance Laboratory, Faculty of KinesiologyUniversity of CalgaryCalgaryCanada
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Fukutani A, Sawatsky A, Leonard T, Herzog W. Contribution of the Achilles tendon to force potentiation in a stretch-shortening cycle. ACTA ACUST UNITED AC 2019; 222:jeb.204032. [PMID: 31278128 DOI: 10.1242/jeb.204032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 07/01/2019] [Indexed: 11/20/2022]
Abstract
Muscle force during concentric contractions is potentiated by a preceding eccentric contraction: a phenomenon known as the stretch-shortening cycle (SSC) effect. Tendon elongation is often considered to be the primary factor for this force potentiation. However, direct examination of the influence of tendon elongation on the SSC effect has not been made. The aim of this study was to evaluate the contribution of tendon elongation to the SSC effect by comparing the magnitude of the SSC effect in the rat soleus with and without the Achilles tendon. The rat soleus was subjected to concentric contractions without pre-activation (CON) and concentric contractions with an eccentric pre-activation (ECC). For the 'with-tendon' condition, the calcaneus was rigidly fixed to a force transducer, while for the 'without-tendon' condition, the soleus was fixed at the muscle-tendon junction. The SSC effect was calculated as the ratio of the mechanical work done during the concentric phase for the ECC and the CON conditions. Substantial and similar (P=0.167) SSC effects were identified for the with-tendon (318±86%) and the without-tendon conditions (271±70%). The contribution of tendon elongation to the SSC effect was negligible for the rat soleus. Other factors, such as pre-activation and residual force enhancement, may cause the large SSC effects and need to be evaluated.
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Affiliation(s)
- Atsuki Fukutani
- Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga, 525-8577, Japan
| | - Andrew Sawatsky
- Faculty of Kinesiology, The University of Calgary, 2500 University Drive, NW, Calgary, AB, T2N 1N4, Canada
| | - Timothy Leonard
- Faculty of Kinesiology, The University of Calgary, 2500 University Drive, NW, Calgary, AB, T2N 1N4, Canada
| | - Walter Herzog
- Faculty of Kinesiology, The University of Calgary, 2500 University Drive, NW, Calgary, AB, T2N 1N4, Canada
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Tomalka A, Röhrle O, Han JC, Pham T, Taberner AJ, Siebert T. Extensive eccentric contractions in intact cardiac trabeculae: revealing compelling differences in contractile behaviour compared to skeletal muscles. Proc Biol Sci 2019; 286:20190719. [PMID: 31138072 DOI: 10.1098/rspb.2019.0719] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Force enhancement (FE) is a phenomenon that is present in skeletal muscle. It is characterized by progressive forces upon active stretching-distinguished by a linear rise in force-and enhanced isometric force following stretching (residual FE (RFE)). In skeletal muscle, non-cross-bridge (XB) structures may account for this behaviour. So far, it is unknown whether differences between non-XB structures within the heart and skeletal muscle result in deviating contractile behaviour during and after eccentric contractions. Thus, we investigated the force response of intact cardiac trabeculae during and after isokinetic eccentric muscle contractions (10% of maximum shortening velocity) with extensive magnitudes of stretch (25% of optimum muscle length). The different contributions of XB and non-XB structures to the total muscle force were revealed by using an actomyosin inhibitor. For cardiac trabeculae, we found that the force-length dynamics during long stretch were similar to the total isometric force-length relation. This indicates that no (R)FE is present in cardiac muscle while stretching the muscle from 0.75 to 1.0 optimum muscle length. This finding is in contrast with the results obtained for skeletal muscle, in which (R)FE is present. Our data support the hypothesis that titin stiffness does not increase with activation in cardiac muscle.
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Affiliation(s)
- André Tomalka
- 1 Department of Motion and Exercise Science, University of Stuttgart , Stuttgart , Germany
| | - Oliver Röhrle
- 2 Institute of Applied Mechanics (Civil Engineering), University of Stuttgart , Stuttgart , Germany.,3 Cluster of Excellence for Simulation Technology (SimTech) , Stuttgart , Germany
| | - June-Chiew Han
- 4 Auckland Bioengineering Institute, The University of Auckland , Auckland , New Zealand
| | - Toan Pham
- 5 Department of Physiology, The University of Auckland , Auckland , New Zealand
| | - Andrew J Taberner
- 4 Auckland Bioengineering Institute, The University of Auckland , Auckland , New Zealand.,6 Department of Engineering Science, The University of Auckland , Auckland , New Zealand
| | - Tobias Siebert
- 1 Department of Motion and Exercise Science, University of Stuttgart , Stuttgart , Germany
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Fukutani A, Shimoho K, Isaka T. Isometric preactivation before active lengthening increases residual force enhancement. Scand J Med Sci Sports 2019; 29:1153-1160. [DOI: 10.1111/sms.13454] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 03/22/2019] [Accepted: 03/29/2019] [Indexed: 11/27/2022]
Affiliation(s)
- Atsuki Fukutani
- Faculty of Sport and Health Science Ritsumeikan University Kusatsu Japan
| | - Kento Shimoho
- Graduate School of Sport and Health Science Ritsumeikan University Kusatsu Japan
| | - Tadao Isaka
- Faculty of Sport and Health Science Ritsumeikan University Kusatsu Japan
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33
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On a three-dimensional constitutive model for history effects in skeletal muscles. Biomech Model Mechanobiol 2019; 18:1665-1681. [DOI: 10.1007/s10237-019-01167-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Accepted: 05/08/2019] [Indexed: 01/07/2023]
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34
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Abstract
Passive force enhancement is defined as the increase in passive, steady-state, isometric force of an actively stretched muscle compared with the same muscle stretched passively to that same length. Passive force enhancement is long lasting, increases with increasing muscle length and increasing stretch magnitudes, contributes to the residual force enhancement in skeletal and cardiac muscle, and is typically only observed at muscle lengths at which passive forces occur naturally. Passive force enhancement is typically equal to or smaller than the total residual force enhancement, it persists when a muscle is deactivated and reactivated, but can be abolished instantaneously when a muscle is shortened quickly from its stretched length. There is strong evidence that the passive force enhancement is caused by the filamentous sarcomeric protein titin, although the detailed molecular mechanisms underlying passive force enhancement remain unknown. Here I propose a tentative mechanism based on experimental evidence that associates passive force enhancement with the shortening of titin's free spring length in the I-band region of sarcomeres. I suggest that this shortening is accomplished by titin binding to actin and that the trigger for titin-actin interactions is associated with the formation of strongly bound cross bridges between actin and myosin that exposes actin attachment sites for titin through movement of the regulatory proteins troponin and tropomyosin.
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Affiliation(s)
- Walter Herzog
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary , Calgary, Alberta , Canada
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35
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Holt NC. Beyond bouncy gaits: The role of multiscale compliance in skeletal muscle performance. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2019; 333:50-59. [DOI: 10.1002/jez.2261] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 01/15/2019] [Accepted: 03/05/2019] [Indexed: 01/21/2023]
Affiliation(s)
- Natalie C. Holt
- Department of Biological Sciences; Northern Arizona University; Flagstaff Arizona
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36
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Johnston K, Moo EK, Jinha A, Herzog W. On sarcomere length stability during isometric and post-active-stretch isometric contractions. J Exp Biol 2019; 222:jeb.209924. [DOI: 10.1242/jeb.209924] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 10/31/2019] [Indexed: 01/18/2023]
Abstract
Sarcomere length (SL) instability and SL non-uniformity have been used to explain fundamental properties of skeletal muscles, such as creep, force depression following active muscle shortening, and residual force enhancement following active stretching of muscles. Regarding residual force enhancement, it has been argued that active muscle stretching causes SL instability, thereby increasing SL non-uniformity. However, we recently showed that SL non-uniformity is not increased by active muscle stretching, but it remains unclear if SL stability is affected by active stretching. Here, we used single myofibrils of rabbit psoas and measured SL non-uniformity and SL instability during isometric contractions and for isometric contractions following active stretching at average SLs corresponding to the descending limb of the force-length relationship. We defined isometric contractions as contractions during which mean SL remained constant. SL instability was quantified by the rate of change of individual SLs over the course of steady state, isometric force; and SL non-uniformity was defined as deviations of SLs from the mean SL at an instant of time. We found that while the mean SL remained constant during isometric contraction, by definition, individual SLs did not. SLs were more stable in the force-enhanced, isometric state following active stretching compared to the isometric reference state. We also found that SL instability was not correlated with the rate of change of SL non-uniformity. Also, SL non-uniformity was not different in the isometric and the post-stretch isometric contractions. We conclude that since SL is more stable but similarly non-uniform in the force-enhanced compared to the corresponding isometric reference contraction, it appears unlikely that either SL instability or SL non-uniformity contribute to the residual force enhancement property of skeletal muscle.
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Affiliation(s)
- Kaleena Johnston
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Eng Kuan Moo
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Azim Jinha
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Walter Herzog
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
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Chen J, Power GA. Modifiability of the history dependence of force through chronic eccentric and concentric biased resistance training. J Appl Physiol (1985) 2018; 126:647-657. [PMID: 30571280 DOI: 10.1152/japplphysiol.00928.2018] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The increase and decrease in steady-state isometric force following active muscle lengthening and shortening are referred to as residual force enhancement (RFE) and force depression (FD), respectively. The RFE and FD states are associated with decreased (activation reduction; AR) and increased (activation increase; AI) neuromuscular activity, respectively. Although the mechanisms have been discussed over the last 60 years, no studies have systematically investigated the modifiability of RFE and FD with training. The purpose of the present study was to determine whether RFE and FD could be modulated through eccentric and concentric biased resistance training. Fifteen healthy young adult men (age: 24 ± 2 yr, weight: 77 ± 8 kg, height: 178 ± 5 cm) underwent 4 wk of isokinetic dorsiflexion training, in which one leg was trained eccentrically (-25°/s) and the other concentrically (+25°/s) over a 50° ankle excursion. Maximal and submaximal (40% maximum voluntary contraction) steady-state isometric torque and EMG values following active lengthening and shortening were compared to purely isometric values at the same joint angles and torque levels. Residual torque enhancement (rTE) decreased by ~36% after eccentric training ( P < 0.05) and increased by ~89% after concentric training ( P < 0.05), whereas residual torque depression (rTD), AR, AI, and optimal angles for torque production were not significantly altered by resistance training ( P ≥ 0.05). It appears that rTE, but not rTD, for the human ankle dorsiflexors is differentially modifiable through contraction type-dependent resistance training. NEW & NOTEWORTHY The history dependence of force production is a property of muscle unexplained by current cross bridge and sliding filament theories. Whether a muscle is actively lengthened (residual force enhancement; RFE) or shortened (force depression) to a given length, the isometric force should be equal to a purely isometric contraction-but it is not! In this study we show that eccentric training decreased RFE, whereas concentric training increased RFE and converted all nonresponders (i.e., not exhibiting RFE) into responders.
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Affiliation(s)
- Jackey Chen
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph , Guelph, Ontario , Canada
| | - Geoffrey A Power
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph , Guelph, Ontario , Canada
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O’Shaughnessy B, Thiyagarajan S. Mechanisms of contractile ring tension production and constriction. Biophys Rev 2018; 10:1667-1681. [PMID: 30456601 PMCID: PMC6297097 DOI: 10.1007/s12551-018-0476-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 10/23/2018] [Indexed: 12/24/2022] Open
Abstract
The contractile ring is a remarkable tension-generating cellular machine that constricts and divides cells into two during cytokinesis, the final stage of the cell cycle. Since the ring's discovery, the parallels with muscle have been emphasized. Both are contractile actomyosin machineries, and long ago, a muscle-like sliding filament mechanism was proposed for the ring. This review focuses on the mechanisms that generate ring tension and constrict contractile rings. The emphasis is on fission yeast, whose contractile ring is sufficiently well characterized that realistic mathematical models are feasible, and possible lessons from fission yeast that may apply to animal cells are discussed. Recent discoveries relevant to the organization in fission yeast rings suggest a stochastic steady-state version of the classic sliding filament mechanism for tension. The importance of different modes of anchoring for tension production and for organizational stability of constricting rings is discussed. Possible mechanisms are discussed that set the constriction rate and enable the contractile ring to meet the technical challenge of maintaining structural integrity and tension-generating capacity while continuously disassembling throughout constriction.
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Affiliation(s)
- Ben O’Shaughnessy
- Department of Chemical Engineering, Columbia University, New York, NY 10027 USA
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39
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Residual force enhancement during submaximal and maximal effort contractions of the plantar flexors across knee angle. J Biomech 2018; 78:70-76. [DOI: 10.1016/j.jbiomech.2018.07.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 07/06/2018] [Accepted: 07/09/2018] [Indexed: 11/23/2022]
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40
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Herzog W. The multiple roles of titin in muscle contraction and force production. Biophys Rev 2018; 10:1187-1199. [PMID: 29353351 PMCID: PMC6082311 DOI: 10.1007/s12551-017-0395-y] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 12/29/2017] [Indexed: 11/27/2022] Open
Abstract
Titin is a filamentous protein spanning the half-sarcomere, with spring-like properties in the I-band region. Various structural, signaling, and mechanical functions have been associated with titin, but not all of these are fully elucidated and accepted in the scientific community. Here, I discuss the primary mechanical functions of titin, including its accepted role in passive force production, stabilization of half-sarcomeres and sarcomeres, and its controversial contribution to residual force enhancement, passive force enhancement, energetics, and work production in shortening muscle. Finally, I provide evidence that titin is a molecular spring whose stiffness changes with muscle activation and actin-myosin-based force production, suggesting a novel model of force production that, aside from actin and myosin, includes titin as a "third contractile" filament. Using this three-filament model of sarcomeres, the stability of (half-) sarcomeres, passive force enhancement, residual force enhancement, and the decrease in metabolic energy during and following eccentric contractions can be explained readily.
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Affiliation(s)
- Walter Herzog
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, T2N 1N4, Canada.
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41
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History dependence of the EMG-torque relationship. J Electromyogr Kinesiol 2018; 41:109-115. [DOI: 10.1016/j.jelekin.2018.05.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 05/18/2018] [Accepted: 05/22/2018] [Indexed: 11/22/2022] Open
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Nishikawa KC, Lindstedt SL, LaStayo PC. Basic science and clinical use of eccentric contractions: History and uncertainties. JOURNAL OF SPORT AND HEALTH SCIENCE 2018; 7:265-274. [PMID: 30356648 PMCID: PMC6189250 DOI: 10.1016/j.jshs.2018.06.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 12/30/2017] [Accepted: 01/09/2018] [Indexed: 05/18/2023]
Abstract
The peculiar attributes of muscles that are stretched when active have been noted for nearly a century. Understandably, the focus of muscle physiology has been primarily on shortening and isometric contractions, as eloquently revealed by A.V. Hill and subsequently by his students. When the sliding filament theory was introduced by A.F. Huxley and H.E. Huxley, it was a relatively simple task to link Hill's mechanical observations to the actions of the cross bridges during these shortening and isometric contractions. In contrast, lengthening or eccentric contractions have remained somewhat enigmatic. Dismissed as necessarily causing muscle damage, eccentric contractions have been much more difficult to fit into the cross-bridge theory. The relatively recent discovery of the giant elastic sarcomeric filament titin has thrust a previously missing element into any discussion of muscle function, in particular during active stretch. Indeed, the unexpected contribution of giant elastic proteins to muscle contractile function is highlighted by recent discoveries that twitchin-actin interactions are responsible for the "catch" property of invertebrate muscle. In this review, we examine several current theories that have been proposed to account for the properties of muscle during eccentric contraction. We ask how well each of these explains existing data and how an elastic filament can be incorporated into the sliding filament model. Finally, we review the increasing body of evidence for the benefits of including eccentric contractions into a program of muscle rehabilitation and strengthening.
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Affiliation(s)
- Kiisa C. Nishikawa
- Center for Bioengineering Innovation and Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Stan L. Lindstedt
- Center for Bioengineering Innovation and Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
- Corresponding author
| | - Paul C. LaStayo
- Department of Physical Therapy and Athletic Training, University of Utah, 520 Wakara Way, Salt Lake City, UT 86011, USA
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Schappacher-Tilp G. Titin-mediated thick filament activation stabilizes myofibrils on the descending limb of their force-length relationship. JOURNAL OF SPORT AND HEALTH SCIENCE 2018; 7:326-332. [PMID: 30356636 PMCID: PMC6189248 DOI: 10.1016/j.jshs.2018.05.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 12/17/2017] [Accepted: 12/29/2017] [Indexed: 06/08/2023]
Abstract
PURPOSE The aim of this study was to extend current half-sarcomere models by involving a recently found force-mediated activation of the thick filament and analyze the effect of this mechanosensing regulation on the length stability of half-sarcomeres arranged in series. METHODS We included a super-relaxed state of myosin motors and its force-dependent activation in a conventional cross-bridge model. We simulated active stretches of a sarcomere consisting of 2 non-uniform half-sarcomeres on the descending limb of the force-length relationship. RESULTS The mechanosensing model predicts that, in a passive sarcomere on the descending limb of the force-length relationship, the longer half-sarcomere has a higher fraction of myosin motors in the on-state than the shorter half-sarcomere. The difference in the number of myosin motors in the on-state ensures that upon calcium-mediated thin filament activation, the force-dependent thick filament activation keeps differences in active force within 20% during an active stretch. In the classical cross-bridge model, the corresponding difference exceeds 80%, leading to great length instabilities. CONCLUSION Our simulations suggest that, in contrast to the classical cross-bridge model, the mechanosensing regulation is able to stabilize a system of non-uniform half-sarcomeres arranged in series on the descending limb of the force-length relationship.
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Herzog W. Why are muscles strong, and why do they require little energy in eccentric action? JOURNAL OF SPORT AND HEALTH SCIENCE 2018; 7:255-264. [PMID: 30356622 PMCID: PMC6189244 DOI: 10.1016/j.jshs.2018.05.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 01/22/2018] [Accepted: 03/24/2018] [Indexed: 05/21/2023]
Abstract
It is well acknowledged that muscles that are elongated while activated (i.e., eccentric muscle action) are stronger and require less energy (per unit of force) than muscles that are shortening (i.e., concentric contraction) or that remain at a constant length (i.e., isometric contraction). Although the cross-bridge theory of muscle contraction provides a good explanation for the increase in force in active muscle lengthening, it does not explain the residual increase in force following active lengthening (residual force enhancement), or except with additional assumptions, the reduced metabolic requirement of muscle during and following active stretch. Aside from the cross-bridge theory, 2 other primary explanations for the mechanical properties of actively stretched muscles have emerged: (1) the so-called sarcomere length nonuniformity theory and (2) the engagement of a passive structural element theory. In this article, these theories are discussed, and it is shown that the last of these-the engagement of a passive structural element in eccentric muscle action-offers a simple and complete explanation for many hitherto unexplained observations in actively lengthening muscle. Although by no means fully proven, the theory has great appeal for its simplicity and beauty, and even if over time it is shown to be wrong, it nevertheless forms a useful framework for direct hypothesis testing.
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de Brito Fontana H, de Campos D, Sakugawa RL. Predictors of residual force enhancement in voluntary contractions of elbow flexors. JOURNAL OF SPORT AND HEALTH SCIENCE 2018; 7:318-325. [PMID: 30356605 PMCID: PMC6189239 DOI: 10.1016/j.jshs.2018.06.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2018] [Revised: 01/24/2018] [Accepted: 02/20/2018] [Indexed: 05/21/2023]
Abstract
BACKGROUND The steady-state increase in muscle force generating potential following a lengthening contraction is called residual force enhancement (RFE). In this study, we aimed to test for differences in torque, electromyographic activity (EMG), and the associated neuromuscular efficiency (NME) between isometric voluntary contractions of elbow flexors preceded and not preceded by a lengthening contraction. The dependence of such differences on (i) stretch amplitude, (ii) the region of the force-length (FxL) relationship where contraction occurs, and (iii) the individual's ability to produce (negative) work during the stretch was investigated. METHODS Sixteen healthy adults participated in the study. Elbow flexor torque, angle, and biceps brachii EMG for purely isometric contractions (reference contractions) and for isometric contractions preceded by active stretches of 20° and 40° were measured at the ascending, plateau, and descending regions of subject-specific FxL curves. All contractions were performed in an isokinetic dynamometer. Two-factor (stretch × FxL region) repeated measures analysis of variance ANOVAs was used to analyze the effect of active stretch on EMG, torque, and NME across conditions. The relationships between mechanical work during stretch-calculated as the torque-angular displacement integral-and the changes in EMG, torque, and NME were analyzed using Pearson correlation. RESULTS In general, torque, EMG, and NME following active stretches differed from the values observed for the purely isometric reference contractions. While although the detailed effects of active stretch on torque and EMG differed between regions of the FxL relationship, NME increased by about 19% for all muscle lengths. Up to 30% of the interindividual variability in torque generating potential change in response to active stretching was accounted for by differences in (negative) work capacity between subjects. CONCLUSION Our results suggest that (i) RFE contributes to "flatten" the elbow flexor torque-angle relationship, favoring torque production at lengths where the purely isometric torques are reduced substantially, and (ii) RFE contributes to a reduction in energy cost of torque production during isometric contractions for the entire operating range.
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Affiliation(s)
- Heiliane de Brito Fontana
- Biological Sciences Center, Federal University of Santa Catarina, Campus Reitor João David Ferreira Lima, Florianópolis, SC 88040-900, Brazil
- Biomechanics Laboratory, Federal University of Santa Catarina, Campus Reitor João David Ferreira Lima, Florianópolis, SC 88040-900, Brazil
| | - Daiani de Campos
- Biomechanics Laboratory, Federal University of Santa Catarina, Campus Reitor João David Ferreira Lima, Florianópolis, SC 88040-900, Brazil
| | - Raphael Luiz Sakugawa
- Biomechanics Laboratory, Federal University of Santa Catarina, Campus Reitor João David Ferreira Lima, Florianópolis, SC 88040-900, Brazil
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Fukutani A, Joumaa V, Herzog W. Influence of residual force enhancement and elongation of attached cross-bridges on stretch-shortening cycle in skinned muscle fibers. Physiol Rep 2018; 5:5/22/e13477. [PMID: 29180479 PMCID: PMC5704075 DOI: 10.14814/phy2.13477] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 09/13/2017] [Accepted: 09/17/2017] [Indexed: 11/24/2022] Open
Abstract
Increased muscle force during stretch‐shortening cycles (SSCs) has been widely examined. However, the mechanisms causing increased muscle force in SSCs remain unknown. The purpose of this study was to determine the influence of residual force enhancement and elongation of attached cross‐bridges on the work enhancement in SSCs. For the Control condition, skinned rabbit soleus fibers were elongated passively from an average sarcomere length of 2.4 to 3.0 μm, activated and then actively shortened to 2.4 μm. For the Transition condition, fibers were elongated actively from an average sarcomere length of 2.4 to 3.0 μm. Two seconds after the end of active lengthening, fibers were actively shortened to 2.4 μm. In the SSC condition, fibers were lengthened actively from an average sarcomere length of 2.4 to 3.0 μm, and then immediately shortened actively to 2.4 μm. Increased muscle force in the SSCs was quantified by the increase in mechanical work during active shortening compared to the mechanical work measured during the purely active shortening contractions. Work enhancement was significantly greater in the SSC compared to the Transition conditions. This difference was associated with the pause given between the active lengthening and shortening phase in the Transition test, which likely resulted in a reduction of the average elongation of the attached cross‐bridges caused by active stretching. Since some work enhancement was still observed in the Transition condition, another factor, for example the stretch‐induced residual force enhancement, must also have contributed to the work enhancement in SSCs.
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Affiliation(s)
- Atsuki Fukutani
- Human Performance Laboratory Faculty of Kinesiology University of Calgary, Calgary, Alberta, Canada .,Japan Society for the Promotion of Science, Chiyoda-ku, Tokyo, Japan.,Research Organization of Science and Technology, Ritsumeikan University, Kusatsu, Shiga, Japan
| | - Venus Joumaa
- Human Performance Laboratory Faculty of Kinesiology University of Calgary, Calgary, Alberta, Canada
| | - Walter Herzog
- Human Performance Laboratory Faculty of Kinesiology University of Calgary, Calgary, Alberta, Canada
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Joumaa V, Bertrand F, Liu S, Poscente S, Herzog W. Does partial titin degradation affect sarcomere length nonuniformities and force in active and passive myofibrils? Am J Physiol Cell Physiol 2018; 315:C310-C318. [PMID: 29768046 DOI: 10.1152/ajpcell.00183.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The aim of this study was to determine the role of titin in preventing the development of sarcomere length nonuniformities following activation and after active and passive stretch by determining the effect of partial titin degradation on sarcomere length nonuniformities and force in passive and active myofibrils. Selective partial titin degradation was performed using a low dose of trypsin. Myofibrils were set at a sarcomere length of 2.4 µm and then passively stretched to sarcomere lengths of 3.4 and 4.4 µm. In the active condition, myofibrils were set at a sarcomere length of 2.8 µm, activated, and actively stretched by 1 µm/sarcomere. The extent of sarcomere length nonuniformities was calculated for each sarcomere as the absolute difference between sarcomere length and the mean sarcomere length of the myofibril. Our main finding is that partial titin degradation does not increase sarcomere length nonuniformities after passive stretch and activation compared with when titin is intact but increases the extent of sarcomere length nonuniformities after active stretch. Furthermore, when titin was partially degraded, active and passive stresses were substantially reduced. These results suggest that titin plays a crucial role in actively stretched myofibrils and is likely involved in active and passive force production.
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Affiliation(s)
- V Joumaa
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, AB, Canada
| | - F Bertrand
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, AB, Canada
| | - S Liu
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, AB, Canada
| | - S Poscente
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, AB, Canada
| | - W Herzog
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, AB, Canada
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Force depression following a stretch-shortening cycle is independent of stretch peak force and work performed during shortening. Sci Rep 2018; 8:1534. [PMID: 29367663 PMCID: PMC5784084 DOI: 10.1038/s41598-018-19657-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 01/03/2018] [Indexed: 11/24/2022] Open
Abstract
The steady-state isometric force following active muscle shortening or lengthening is smaller (force depression; FD) or greater (residual force enhancement; RFE) than a purely isometric contraction at the corresponding length. The mechanisms behind these phenomena remain not fully understood, with few studies investigating the effects of FD and RFE in stretch-shortening cycles (SSC). The purpose of this study was to investigate the influence of RFE and peak force at the end of the stretch phase on the steady-state isometric force following shortening. Isometric thumb adduction force measurements were preceded by an isometric, a shortening contraction to induce FD, and SSCs at different stretch speeds (15°/s, 60°/s, and 120°/s). The different peak force values at the end of stretch and the different amounts of work performed during shortening did not influence the steady-state isometric force at the end of the SSC. We conclude that the FD following SSC depends exclusively on the amount of RFE established in the initial stretch phase in situations where the timing and contractile conditions of the shortening phase are kept constant .
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DuVall MM, Jinha A, Schappacher-Tilp G, Leonard TR, Herzog W. Differences in titin segmental elongation between passive and active stretch in skeletal muscle. ACTA ACUST UNITED AC 2017; 220:4418-4425. [PMID: 28970245 DOI: 10.1242/jeb.160762] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 09/26/2017] [Indexed: 12/25/2022]
Abstract
Since the 1950s, muscle contraction has been explained using a two-filament system in which actin and myosin exclusively dictate active force in muscle sarcomeres. Decades later, a third filament called titin was discovered. This titin filament has recently been identified as an important regulator of active force, but has yet to be incorporated into contemporary theories of muscle contraction. When sarcomeres are actively stretched, a substantial and rapid increase in force occurs, which has been suggested to arise in part from titin-actin binding that is absent in passively stretched sarcomeres. However, there is currently no direct evidence for such binding within muscle sarcomeres. Therefore, we aimed to determine whether titin binds to actin in actively but not in passively stretched sarcomeres by observing length changes of proximal and distal titin segments in the presence and absence of calcium. We labeled I-band titin with fluorescent F146 antibody in rabbit psoas myofibrils and tracked segmental elongations during passive (no calcium) and active (high calcium) stretch. Without calcium, proximal and distal segments of titin elongated as expected based on their free spring properties. In contrast, active stretch differed statistically from passive stretch, demonstrating that calcium activation increases titin segment stiffness, but not in an actin-dependent manner. The consistent elongation of the proximal segment was contrary to what was expected if titin's proximal segment was attached to actin. This rapid calcium-dependent change in titin stiffness likely contributes to active muscle force regulation in addition to actin and myosin.
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Affiliation(s)
- Michael M DuVall
- Human Performance Lab., University of Calgary, Calgary, AB, Canada T2N 1N4 .,Center for Bioengineering Innovation, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Azim Jinha
- Human Performance Lab., University of Calgary, Calgary, AB, Canada T2N 1N4
| | - Gudrun Schappacher-Tilp
- Department of Mathematics and Scientific Computing, Karl-Franzens-Universitat Graz, 8010 Graz, Austria
| | - Timothy R Leonard
- Human Performance Lab., University of Calgary, Calgary, AB, Canada T2N 1N4
| | - Walter Herzog
- Human Performance Lab., University of Calgary, Calgary, AB, Canada T2N 1N4
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Heidlauf T, Klotz T, Rode C, Siebert T, Röhrle O. A continuum-mechanical skeletal muscle model including actin-titin interaction predicts stable contractions on the descending limb of the force-length relation. PLoS Comput Biol 2017; 13:e1005773. [PMID: 28968385 PMCID: PMC5638554 DOI: 10.1371/journal.pcbi.1005773] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 10/12/2017] [Accepted: 09/12/2017] [Indexed: 11/18/2022] Open
Abstract
Contractions on the descending limb of the total (active + passive) muscle force-length relationship (i. e. when muscle stiffness is negative) are expected to lead to vast half-sarcomere-length inhomogeneities. This is however not observed in experiments-vast half-sarcomere-length inhomogeneities can be absent in myofibrils contracting in this range, and initial inhomogeneities can even decrease. Here we show that the absence of half-sarcomere-length inhomogeneities can be predicted when considering interactions of the semi-active protein titin with the actin filaments. Including a model of actin-titin interactions within a multi-scale continuum-mechanical model, we demonstrate that stability, accurate forces and nearly homogeneous half-sarcomere lengths can be obtained on the descending limb of the static total force-length relation. This could be a key to durable functioning of the muscle because large local stretches, that might harm, for example, the transverse-tubule system, are avoided.
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Affiliation(s)
- Thomas Heidlauf
- Institute of Applied Mechanics (CE), University of Stuttgart, Stuttgart, Germany
- Stuttgart Research Centre for Simulation Technology (SRC SimTech), University of Stuttgart, Stuttgart, Germany
| | - Thomas Klotz
- Institute of Applied Mechanics (CE), University of Stuttgart, Stuttgart, Germany
- Stuttgart Research Centre for Simulation Technology (SRC SimTech), University of Stuttgart, Stuttgart, Germany
| | - Christian Rode
- Institute of Motion Science, Friedrich-Schiller-University, Jena, Germany
| | - Tobias Siebert
- Department of Sport and Motion Science, University of Stuttgart, Stuttgart, Germany
| | - Oliver Röhrle
- Institute of Applied Mechanics (CE), University of Stuttgart, Stuttgart, Germany
- Stuttgart Research Centre for Simulation Technology (SRC SimTech), University of Stuttgart, Stuttgart, Germany
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