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Barbi C, Temesi J, Giuriato G, Laginestra FG, Martignon C, Moro T, Schena F, Venturelli M, Vernillo G. Skeletal muscle fiber type and TMS-induced muscle relaxation in unfatigued and fatigued knee-extensor muscles. Am J Physiol Regul Integr Comp Physiol 2024; 326:R438-R447. [PMID: 38525536 DOI: 10.1152/ajpregu.00174.2023] [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: 07/14/2023] [Revised: 03/14/2024] [Accepted: 03/15/2024] [Indexed: 03/26/2024]
Abstract
The force drop after transcranial magnetic stimulation (TMS) delivered to the motor cortex during voluntary muscle contractions could inform about muscle relaxation properties. Because of the physiological relation between skeletal muscle fiber-type distribution and size and muscle relaxation, TMS could be a noninvasive index of muscle relaxation in humans. By combining a noninvasive technique to record muscle relaxation in vivo (TMS) with the gold standard technique for muscle tissue sampling (muscle biopsy), we investigated the relation between TMS-induced muscle relaxation in unfatigued and fatigued states, and muscle fiber-type distribution and size. Sixteen participants (7F/9M) volunteered to participate. Maximal knee-extensor voluntary isometric contractions were performed with TMS before and after a 2-min sustained maximal voluntary isometric contraction. Vastus lateralis muscle tissue was obtained separately from the participants' dominant limb. Fiber type I distribution and relative cross-sectional area of fiber type I correlated with TMS-induced muscle relaxation at baseline (r = 0.67, adjusted P = 0.01; r = 0.74, adjusted P = 0.004, respectively) and normalized TMS-induced muscle relaxation as a percentage of baseline (r = 0.50, adjusted P = 0.049; r = 0.56, adjusted P = 0.031, respectively). The variance in the normalized peak relaxation rate at baseline (59.8%, P < 0.001) and in the fatigue resistance (23.0%, P = 0.035) were explained by the relative cross-sectional area of fiber type I to total fiber area. Fiber type I proportional area influences TMS-induced muscle relaxation, suggesting TMS as an alternative method to noninvasively inform about skeletal muscle relaxation properties.NEW & NOTEWORTHY Transcranial magnetic stimulation (TMS)-induced muscle relaxation reflects intrinsic muscle contractile properties by interrupting the drive from the central nervous system during voluntary muscle contractions. We showed that fiber type I proportional area influences the TMS-induced muscle relaxation, suggesting that TMS could be used for the noninvasive estimation of muscle relaxation in unfatigued and fatigued human muscles when the feasibility of more direct method to study relaxation properties (i.e., muscle biopsy) is restricted.
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Affiliation(s)
- Chiara Barbi
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - John Temesi
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom
| | - Gaia Giuriato
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
- Surgical, Medical and Dental Department of Morphological Sciences Related to Transplant, Oncology and Regenerative Medicine, University of Modena and Reggio Emilia, Modena, Italy
| | | | - Camilla Martignon
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Tatiana Moro
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Federico Schena
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Massimo Venturelli
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
- Department of Internal Medicine, University of Utah, Salt Lake City, Utah, United States
| | - Gianluca Vernillo
- Department of Biomedical Sciences for Health, Università degli Studi di Milano, Milan, Italy
- Department of Social Sciences, University of Alberta, Camrose, Alberta, Canada
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Lunde PK, Manfra O, Støle TP, Lunde M, Martinsen M, Carlson CR, Louch WE. Polyarginine Cell-Penetrating Peptides Bind and Inhibit SERCA2. Cells 2023; 12:2358. [PMID: 37830576 PMCID: PMC10571751 DOI: 10.3390/cells12192358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 09/19/2023] [Accepted: 09/21/2023] [Indexed: 10/14/2023] Open
Abstract
Cell-penetrating peptides (CPPs) are short peptide sequences that have the ability to cross the cell membrane and deliver cargo. Although it is critical that CPPs accomplish this task with minimal off-target effects, such actions have in many cases not been robustly screened. We presently investigated whether the commonly used CPPs TAT and the polyarginines Arg9 and Arg11 exert off-target effects on cellular Ca2+ homeostasis. In experiments employing myocytes and homogenates from the cardiac left ventricle or soleus muscle, we observed marked inhibition of Ca2+ recycling into the sarcoplasmic reticulum (SR) following incubation with polyarginine CPPs. In both tissues, the rate of SR Ca2+ leak remained unchanged, indicating that protracted Ca2+ removal from the cytosol stemmed from inhibition of the SR Ca2+ ATPase 2 (SERCA2). No such inhibition occurred following treatment with TAT, or in preparations from the SERCA1-expressing extensor digitorum longus muscle. Experiments in HEK cells overexpressing individual SERCA isoforms confirmed that polyarginine incubation specifically inhibited the activity of SERCA2a and 2b, but not SERCA1 or 3. The attenuation of SERCA2 activity was not dependent on the presence of phospholamban, and ELISA-based analyses rather revealed direct interaction between the polyarginines and the actuator domain of the protein. Surface plasmon resonance experiments confirmed strong binding within this region of SERCA2, and slow dissociation between the two species. Based on these observations, we urge caution when employing polyarginine CPPs. Indeed, as SERCA2 is expressed in diverse cell types, the wide-ranging consequences of SERCA2 binding and inhibition should be anticipated in both experimental and therapeutic settings.
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Affiliation(s)
| | | | | | | | | | - Cathrine Rein Carlson
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, 0450 Oslo, Norway; (P.K.L.); (O.M.); (T.P.S.); (M.L.); (M.M.); (W.E.L.)
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Cogliati M, Cudicio A, Benedini M, Cabral HV, Negro F, Reggiani C, Orizio C. Influence of age on force and re-lengthening dynamics after tetanic stimulation withdrawal in the tibialis anterior muscle. Eur J Appl Physiol 2023; 123:1825-1836. [PMID: 37071199 PMCID: PMC10363076 DOI: 10.1007/s00421-023-05198-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 04/05/2023] [Indexed: 04/19/2023]
Abstract
PURPOSE During alternate movements across a joint, the changeover from one direction of rotation to the opposite may be influenced by the delay and rate of tension reduction and the compliance to re-lengthening of the previously active muscle group. Given the aging process may affect the above-mentioned factors, this work aimed to compare the dynamics of both the ankle torque decline and muscle re-lengthening, mirrored by mechanomyogram (MMG), in the tibialis anterior because of its important role in gait. METHODS During the relaxation phase, after a supramaximal 35 Hz stimulation applied at the superficial motor point, in 20 young (Y) and 20 old (O) subjects, the torque (T) and MMG dynamics characteristics were measured. RESULTS The T and MMG analysis provided: (I) the beginning of the decay after cessation of stimulation (T: 22.51 ± 5.92 ms [Y] and 51.35 ± 15.21 ms [O]; MMG: 27.38 ± 6.93 ms [Y] and 61.41 ± 18.42 ms [O]); (II) the maximum rate of reduction (T: - 110.4 ± 45.56 Nm/s [Y] and - 52.72 ± 32.12 Nm/s [O]; MMG: - 24.47 ± 10.95 mm/s [Y] and - 13.76 ± 6.54 mm/s [O]); (III) the muscle compliance, measuring the MMG reduction of every 10% reduction of torque (bin 20-10%: 15.69 ± 7.5[Y] and 10.8 ± 3.3 [O]; bin 10-0%: 22.12 ± 10.3 [Y] and 17.58 ± 5.6 [O]). CONCLUSION Muscle relaxation results are different in Y and O and can be monitored by a non-invasive method measuring physiological variables of torque and re-lengthening dynamics at the end of the electromechanical coupling previously induced by the neuromuscular stimulation.
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Affiliation(s)
- M. Cogliati
- Department of Clinical and Experimental Sciences, University of Brescia Viale Europa, 11, 25123 Brescia, Italy
| | - A. Cudicio
- Department of Clinical and Experimental Sciences, University of Brescia Viale Europa, 11, 25123 Brescia, Italy
| | - M. Benedini
- Department of Clinical and Experimental Sciences, University of Brescia Viale Europa, 11, 25123 Brescia, Italy
| | - H. V. Cabral
- Department of Clinical and Experimental Sciences, University of Brescia Viale Europa, 11, 25123 Brescia, Italy
| | - F. Negro
- Department of Clinical and Experimental Sciences, University of Brescia Viale Europa, 11, 25123 Brescia, Italy
- Centre of Research on the Neuromuscular Function and the Adapted Motor Activity, University of Brescia Viale Europa, 11, 25123 Brescia, Italy
| | - C. Reggiani
- Department of Biomedical Sciences, University of Padova, Padova, Italy
- Science and Research Center, ZRS, Koper, Slovenia
| | - C. Orizio
- Department of Clinical and Experimental Sciences, University of Brescia Viale Europa, 11, 25123 Brescia, Italy
- Centre of Research on the Neuromuscular Function and the Adapted Motor Activity, University of Brescia Viale Europa, 11, 25123 Brescia, Italy
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Xenofondos A, Papavasileiou A, Bassa E, Vrabas IS, Patikas DA. Postactivation Potentiation and the Asynchronous Action of Muscular and Neural Responses. Int J Sports Physiol Perform 2023:1-9. [PMID: 37295786 DOI: 10.1123/ijspp.2022-0336] [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: 09/02/2022] [Revised: 03/22/2023] [Accepted: 05/02/2023] [Indexed: 06/12/2023]
Abstract
PURPOSE This study examined the underlying mechanisms of postactivation potentiation and the time course of muscular- and neural-related variables. METHODS Fourteen trained males executed 4 sets of six 6-second maximum isometric conditioning plantar flexions, with 15 seconds and 2 minutes of interval between the contractions and sets, respectively. Peak twitch torque (TT), rate of torque development, time to peak torque, half relaxation time, and the neural-related variables of H-reflex and electromyogram, normalized to the maximum M-wave (H/M and RMS/M, respectively), were evaluated, as well as the level of the voluntary activation, assessed by the twitch interpolation technique. All neural-related variables were analyzed for the trial within each set when TT was maximal and for the trial within each set when the neural-related variable itself was maximal. RESULTS Compared with the baseline measures, TT and rate of torque development significantly increased in all sets (P < .001), whereas time to peak torque and half relaxation time significantly decreased in sets 1 to 4 and 2 to 4, respectively (P < .001). However, H/M and the RMS/M did not change for the repetition of each set for which the TT was maximal (P > .05). Interestingly, the within-set maximum H/M ratio of the lateral gastrocnemius muscle revealed a significant increase in all sets (P < .05), compared with the baseline measures. CONCLUSION One set of 4 contractions with 6-second duration is sufficient to cause postactivation potentiation for most participants, whereas peak TT augmentation does not coincide with changes in the examined neural-related variables. Further experiments should consider the time lag on their maximal values and their inherent between-participants variability.
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Affiliation(s)
- Anthi Xenofondos
- Physical Education and Sport Sciences, Frederick University, Nicosia,Cyprus
- Faculty of Physical Education and Sport Sciences, Aristotle University of Thessaloniki, Thessaloniki,Greece
| | - Anastasia Papavasileiou
- Faculty of Physical Education and Sport Sciences, Aristotle University of Thessaloniki, Thessaloniki,Greece
| | - Eleni Bassa
- Faculty of Physical Education and Sport Sciences, Aristotle University of Thessaloniki, Thessaloniki,Greece
| | - Ioannis S Vrabas
- Faculty of Physical Education and Sport Sciences, Aristotle University of Thessaloniki, Thessaloniki,Greece
| | - Dimitrios A Patikas
- Faculty of Physical Education and Sport Sciences, Aristotle University of Thessaloniki, Thessaloniki,Greece
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Powell AR, Deban SM, Lappin AK. Sustained force production by the jaw-adductor muscles of a megalophagous frog, Ceratophrys cranwelli. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2023; 339:437-445. [PMID: 36855228 DOI: 10.1002/jez.2690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 01/11/2023] [Accepted: 02/14/2023] [Indexed: 03/02/2023]
Abstract
Most frogs have weak jaws that play a relatively minor role in tongue-mediated prey capture. Horned frogs (Ceratophrys spp.), however, follow the projection of a large tongue with a vice-like grip of their jaws to hold and immobilize prey. Prey include relatively large vertebrates, which they may restrain for minutes to possibly hours. High endurance behaviors, such as prolonged biting, require that muscles be capable of sustained force production. The feeding behavior of Ceratophrys suggests that their jaw-adductor muscles may be capable of powering sustained bites for long periods. We examined the capacity for sustained bite force by conducting an in situ experiment during which we measured bite force while bilaterally and supramaximally stimulating the jaw-adductor muscles of euthanized Cranwell's horned frogs (C. cranwelli). Muscles were stimulated for at least 60 min with a series of tetanic trains, with one experiment lasting over 6 h. We found that a significant sustained force develops during the first few minutes of the experiment, and this force is present between tetanic trains when the muscles are not being stimulated. The sustained force persists long after tetanic forces are barely detectable. The observed sustained force phenomenon parallels that observed for the jaw-adductor muscles of alligator lizards (Elgaria), another animal capable of sustained biting. The ability to bite with sustained and significant force by C. cranwelli may be facilitated by a configuration of different muscle fiber types, such as slow tonic fibers, as well as specializations in the muscle fibers that mitigate the effects of fatigue.
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Affiliation(s)
- Anthony R Powell
- Biological Sciences Department, California State Polytechnic University, Pomona, California, USA
| | - Stephen M Deban
- Department of Integrative Biology, University of South Florida, Tampa, Florida, USA
| | - A Kristopher Lappin
- Biological Sciences Department, California State Polytechnic University, Pomona, California, USA
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Muñoz-Pérez I, Varela-Sanz A, Lago-Fuentes C, Navarro-Patón R, Mecías-Calvo M. Central and Peripheral Fatigue in Recreational Trail Runners: A Pilot Study. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 20:402. [PMID: 36612727 PMCID: PMC9819577 DOI: 10.3390/ijerph20010402] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 12/09/2022] [Accepted: 12/22/2022] [Indexed: 06/17/2023]
Abstract
BACKGROUND Understanding fatigue mechanisms is crucial for exercise performance. However, scientific evidence on non-invasive methods for assessing fatigue in trail running competitions is scarce, especially when vertical kilometer trail running races (VK) are considered. The main purpose of this study was to assess the autonomic nervous system (ANS) activity (i.e., central fatigue) and the state of muscle activation (i.e., peripheral fatigue) before and after a VK competition. METHODS A cross-sectional pilot study was performed. After applying inclusion/exclusion criteria, 8 recreational male trail runners (31.63 ± 7.21 yrs, 1.75 m ± 0.05 m, 70.38 ± 5.41 kg, BMI: 22.88 ± 0.48, running experience: 8.0 ± 3.63 yrs, weekly training volume: 58.75 ± 10.35 km) volunteered to participate and were assessed for both central (i.e., via heart rate variability, HRV) and peripheral (via tensiomyography, TMG) fatigue before and after a VK race. RESULTS After the VK, resting heart rate, RMSSD (p = 0.01 for both) and SDNN significantly decreased (p = 0.02), while the stress score and the sympathetic-parasympathetic ratio increased (p = 0.01 and p = 0.02, respectively). The TMG analyses suggest that runners already suffered peripheral fatigue before the VK and that 20-30 min are enough for muscular recovery after the race. In summary, our data suggest that participants experienced a pre-competition fatigue status. Further longitudinal studies are necessary to investigate the mechanisms underlying fatigue during trail running races, while training periodization and tapering strategies could play a key role for minimizing pre-competition fatigue status.
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Affiliation(s)
- Iker Muñoz-Pérez
- Facultad de Ciencias de la Educación y Deporte, Universidad de Deusto, 48007 Bilbao, Spain
| | - Adrián Varela-Sanz
- Physical and Sports Education Department, Faculty of Sport Sciences and Physical Education, University of A Coruna, 15179 A Coruna, Spain
| | - Carlos Lago-Fuentes
- Facultad de Ciencias de la Salud, Universidad Europea del Atlántico, 39011 Santander, Spain
| | - Rubén Navarro-Patón
- Facultad de Formación del Profesorado, Universidade de Santiago de Compostela, 27001 Lugo, Spain
| | - Marcos Mecías-Calvo
- Facultad de Formación del Profesorado, Universidade de Santiago de Compostela, 27001 Lugo, Spain
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Nguyen A, Balaban JP, Azizi E, Talmadge RJ, Lappin AK. Fatigue resistant jaw muscles facilitate long-lasting courtship behaviour in the southern alligator lizard ( Elgaria multicarinata). Proc Biol Sci 2020; 287:20201578. [PMID: 32962547 PMCID: PMC7542809 DOI: 10.1098/rspb.2020.1578] [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] [Indexed: 11/12/2022] Open
Abstract
The southern alligator lizard (Elgaria multicarinata) exhibits a courtship behaviour during which the male firmly grips the female's head in his jaws for many hours at a time. This extreme behaviour counters the conventional wisdom that reptilian muscle is incapable of powering high-endurance behaviours. We conducted in situ experiments in which the jaw-adductor muscles of lizards were stimulated directly while bite force was measured simultaneously. Fatigue tests were performed by stimulating the muscles with a series of tetanic trains. Our results show that a substantial sustained force gradually develops during the fatigue test. This sustained force persists after peak tetanic forces have declined to a fraction of their initial magnitude. The observed sustained force during in situ fatigue tests is consistent with the courtship behaviour of these lizards and probably reflects physiological specialization. The results of molecular analysis reveal that the jaw muscles contain masticatory and tonic myosin fibres. We propose that the presence of tonic fibres may explain the unusual sustained force properties during mate-holding behaviour. The characterization of muscle properties that facilitate extreme performance during specialized behaviours may reveal general mechanisms of muscle function, especially when done in light of convergently evolved systems exhibiting similar performance characteristics.
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Affiliation(s)
- Allyn Nguyen
- Biological Sciences Department, California State Polytechnic University, Pomona, CA 91768, USA
| | - Jordan P Balaban
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA
| | - Emanuel Azizi
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA
| | - Robert J Talmadge
- Biological Sciences Department, California State Polytechnic University, Pomona, CA 91768, USA
| | - A Kristopher Lappin
- Biological Sciences Department, California State Polytechnic University, Pomona, CA 91768, USA
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Hucteau E, Jubeau M, Cornu C, Cattagni T. Is there an intermuscular relationship in voluntary activation capacities and contractile kinetics? Eur J Appl Physiol 2020; 120:513-526. [PMID: 31925519 DOI: 10.1007/s00421-019-04299-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 12/30/2019] [Indexed: 01/14/2023]
Abstract
PURPOSE The force-generating capacities of human skeletal muscles are interrelated, highlighting a common construct of limb strength. This study aimed to further determine whether there is an intermuscular relationship in maximal voluntary activation capacities and contractile kinetics of human muscles. METHODS Twenty-six young healthy individuals participated in this study. Isometric maximal voluntary contraction (MVC) torque, voluntary activation level (VAL), and doublet twitch contractile kinetics (contraction time and half-relaxation time) evoked by a paired supramaximal peripheral nerve stimulation at 100 Hz were obtained in elbow flexors, knee extensors, plantar flexors and dorsiflexors of the dominant limb. RESULTS Peak MVC torque had significant positive correlations between all muscle group pairs (all P values < 0.01). A significant positive correlation for VAL was found only between knee extensors and plantar flexors (r = 0.60, P < 0.01). There were no significant correlations between all muscle group pairs for doublet twitch contraction time and doublet twitch half-relaxation time. DISCUSSION These results show that there is a partial common construct of maximal voluntary activation capacities that only concerns muscle groups that have incomplete activation during MVC (i.e., knee extensors and plantar flexors). This suggests that the common construct of MVC strength between these two muscle groups is partly influenced by neural mechanisms. The lack of intermuscular relationship of contractile kinetics showed that there is no common construct of muscle contractile kinetics, as assessed in vivo by investigating the time-course of evoked doublet twitch contractions.
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Affiliation(s)
- Elyse Hucteau
- Laboratoire "Motricité, Interactions, Performance" EA 4334, Faculty of Sport Sciences, UFR STAPS, University of Nantes, 25 bis Boulevard Guy Mollet-BP 72206, 44 322, Nantes cedex 3, France
| | - Marc Jubeau
- Laboratoire "Motricité, Interactions, Performance" EA 4334, Faculty of Sport Sciences, UFR STAPS, University of Nantes, 25 bis Boulevard Guy Mollet-BP 72206, 44 322, Nantes cedex 3, France
| | - Christophe Cornu
- Laboratoire "Motricité, Interactions, Performance" EA 4334, Faculty of Sport Sciences, UFR STAPS, University of Nantes, 25 bis Boulevard Guy Mollet-BP 72206, 44 322, Nantes cedex 3, France
| | - Thomas Cattagni
- Laboratoire "Motricité, Interactions, Performance" EA 4334, Faculty of Sport Sciences, UFR STAPS, University of Nantes, 25 bis Boulevard Guy Mollet-BP 72206, 44 322, Nantes cedex 3, France.
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Gago PR, Arndt A, Marques MC, Marinho DA, Ekblom MM. Effects of post activation potentiation on electromechanical delay. Clin Biomech (Bristol, Avon) 2019; 70:115-122. [PMID: 31476603 DOI: 10.1016/j.clinbiomech.2019.08.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 07/31/2019] [Accepted: 08/01/2019] [Indexed: 02/07/2023]
Abstract
Electromechanical delay (EMD) presumably depends upon both contractile and tensile factors. It has recently been used as an indirect measure of muscle tendon stiffness to study adaptations to stretching and training. The aim of the present study was to investigate whether contractile properties induced by a 6 s maximum voluntary isometric contraction (MVIC) could affect EMD without altering passive muscle tendon stiffness or stiffness index. Plantar flexor twitches were evoked via electrical stimulation of the tibial nerve in eight highly trained male sprinters before and after a 6 s MVIC in passive isometric or passively shortening or lengthening muscles. For each twitch, EMD, twitch contractile properties and SOLM-Wave were measured. Passive muscle tendon stiffness was measured from the slope of the relation between torque and ankle angle during controlled passive dorsal flexion and stiffness index by curve-fitting the torque angle data using a second-order polynomial function. EMD did not differ between isometric, lengthening or shortening movements. EMD was reduced by up to 11.56 ± 5.64% immediately after the MVIC and stayed depressed for up to 60 s after conditioning. Peak twitch torque and rate of torque development were potentiated by up to 119.41 ± 37.15% and 116.06 ± 37.39%, respectively. Rising time was reduced by up to 14.46 ± 7.22%. No significant changes occurred in passive muscle tendon stiffness or stiffness index. Using a conditioning MVIC, it was shown that there was an acute enhancement of contractile muscle properties as well as a significant reduction in EMD with no corresponding changes in stiffness. Therefore, caution should be taken when using and interpreting EMD as a proxy for muscle tendon stiffness.
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Affiliation(s)
- Paulo R Gago
- Biomechanics and Motor Control Laboratory, The Swedish School of Sport and Health Sciences (GIH), Stockholm, Sweden
| | - Anton Arndt
- Biomechanics and Motor Control Laboratory, The Swedish School of Sport and Health Sciences (GIH), Stockholm, Sweden; Institution CLINTEC, Karolinska Institute, Stockholm, Sweden
| | - Mário C Marques
- University of Beira Interior (UBI), Covilhã, Portugal; Research Centre in Sports Sciences, Health Sciences and Human Development (CIDESD), Covilhã, Portugal
| | - Daniel A Marinho
- University of Beira Interior (UBI), Covilhã, Portugal; Research Centre in Sports Sciences, Health Sciences and Human Development (CIDESD), Covilhã, Portugal.
| | - Maria M Ekblom
- Biomechanics and Motor Control Laboratory, The Swedish School of Sport and Health Sciences (GIH), Stockholm, Sweden
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Blackwood SJ, Katz A. Isoproterenol enhances force production in mouse glycolytic and oxidative muscle via separate mechanisms. Pflugers Arch 2019; 471:1305-1316. [PMID: 31451903 PMCID: PMC6814637 DOI: 10.1007/s00424-019-02304-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 07/22/2019] [Accepted: 08/13/2019] [Indexed: 02/04/2023]
Abstract
Fight or flight is a biologic phenomenon that involves activation of β-adrenoceptors in skeletal muscle. However, how force generation is enhanced through adrenergic activation in different muscle types is not fully understood. We studied the effects of isoproterenol (ISO, β-receptor agonist) on force generation and energy metabolism in isolated mouse soleus (SOL, oxidative) and extensor digitorum longus (EDL, glycolytic) muscles. Muscles were stimulated with isometric tetanic contractions and analyzed for metabolites and phosphorylase activity. Under conditions of maximal force production, ISO enhanced force generation markedly more in SOL (22%) than in EDL (8%). Similarly, during a prolonged tetanic contraction (30 s for SOL and 10 s for EDL), ISO-enhanced the force × time integral more in SOL (25%) than in EDL (3%). ISO induced marked activation of phosphorylase in both muscles in the basal state, which was associated with glycogenolysis (less in SOL than in EDL), and in EDL only, a significant decrease (16%) in inorganic phosphate (Pi). ATP turnover during sustained contractions (1 s EDL, 5 s SOL) was not affected by ISO in EDL, but essentially doubled in SOL. Under conditions of maximal stimulation, ISO has a minor effect on force generation in EDL that is associated with a decrease in Pi, whereas ISO has a marked effect on force generation in SOL that is associated with an increase in ATP turnover. Thus, phosphorylase functions as a phosphate trap in ISO-mediated force enhancement in EDL and as a catalyzer of ATP supply in SOL.
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Affiliation(s)
- Sarah J Blackwood
- Åstrand Laboratory of Work Physiology, Swedish School of Sport and Health Sciences, GIH, Box 5626, S-114 86, Stockholm, Sweden
| | - Abram Katz
- Åstrand Laboratory of Work Physiology, Swedish School of Sport and Health Sciences, GIH, Box 5626, S-114 86, Stockholm, Sweden.
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Glass LD, Cheng AJ, MacIntosh BR. Role of Ca 2+ in changing active force during intermittent submaximal stimulation in intact, single mouse muscle fibers. Pflugers Arch 2018; 470:1243-1254. [PMID: 29671103 PMCID: PMC6060763 DOI: 10.1007/s00424-018-2143-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 04/02/2018] [Accepted: 04/04/2018] [Indexed: 12/27/2022]
Abstract
Fatigue of single mouse fibers during repeated high-frequency stimulation results initially from decreased Ca2+ sensitivity while free myoplasmic calcium concentration ([Ca2+]m) increases, followed by decreasing [Ca2+]m. Recovery of active force with low-frequency stimulation is slow and persistent fatigue results from low [Ca2+]m. However, the consequences of intermittent submaximal contractions are not known. The aim of the present study was to investigate the changes in [Ca2+]m and active force during intermittent submaximal contractions and subsequent recovery. Single fibers of mouse flexor digitorum brevis muscles at 32 °C were stimulated with 40 or 50 Hz, for 350 ms every 2 s for 2 min and then every 1 s until < 40% of initial force. Values obtained during the intermittent stimulation were compared with a control force-[Ca2+]m relationship. A "P"-shaped pattern in the force-[Ca2+]m relationship was observed during intermittent stimulation. Early in the intermittent stimulation, [Ca2+]m increased while active force decreased. Subsequent force potentiation was accompanied by increased Ca2+ sensitivity. Later, as active force declined, [Ca2+]m decreased significantly (p < 0.001). This was followed, in the final phase, by a significant decrease in Ca2+ sensitivity determined by [Ca2+]m at half-maximal force (Ca50) (p = 0.001). Low-frequency fatigue persisted during recovery while Ca50 was not significantly different from prefatigue (p > 0.5). In conclusion, the main mechanism of fatigue is due to decreases in both [Ca2+]m and Ca2+ sensitivity following the initial force potentiation. The intermittent submaximal contractions resulted in persistent low-frequency fatigue seen during recovery, which was explained by depressed [Ca2+]m with no change in Ca2+ sensitivity.
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Affiliation(s)
- Lisa D. Glass
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta T2N 1N4 Canada
| | - Arthur J. Cheng
- Department of Physiology and Pharmacology, Karolinska Institutet, SE-171 77 Stockholm, Sweden
| | - Brian R. MacIntosh
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta T2N 1N4 Canada
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12
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Jones RL, Barnett CT, Davidson J, Maritza B, Fraser WD, Harris R, Sale C. β-alanine supplementation improves in-vivo fresh and fatigued skeletal muscle relaxation speed. Eur J Appl Physiol 2017; 117:867-879. [PMID: 28349262 PMCID: PMC5388709 DOI: 10.1007/s00421-017-3569-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 02/11/2017] [Indexed: 11/30/2022]
Abstract
Purpose In fresh muscle, supplementation with the rate-limiting precursor of carnosine, β-alanine (BA), results in a decline in muscle half-relaxation time (HRT) potentially via alterations to calcium (Ca2+) handling. Accumulation of hydrogen cation (H+) has been shown to impact Ca2+ signalling during muscular contraction, carnosine has the potential to serve as a cytoplasmic regulator of Ca2+ and H+ coupling, since it binds to both ions. The present study examined the effect of BA supplementation on intrinsic in-vivo isometric knee extensor force production and muscle contractility in both fresh and fatigued human skeletal muscle assessed during voluntary and electrically evoked (nerve and superficial muscle stimulation) contractions. Methods Twenty-three males completed two experimental sessions, pre- and post- 28 day supplementation with 6.4 g.day−1 of BA (n = 12) or placebo (PLA; n = 11). Isometric force was recorded during a series of voluntary and electrically evoked knee extensor contractions. Results BA supplementation had no effect on voluntary or electrically evoked isometric force production, or twitch electromechanical delay and time-to-peak tension. There was a significant decline in muscle HRT in fresh and fatigued muscle conditions during both resting (3 ± 13%; 19 ± 26%) and potentiated (1 ± 15%; 2 ± 20%) twitch contractions. Conclusions The mechanism for reduced HRT in fresh and fatigued skeletal muscle following BA supplementation is unclear. Due to the importance of muscle relaxation on total energy consumption, especially during short, repeated contractions, BA supplementation may prove to be beneficial in minimising contractile slowing induced by fatigue. Trial registration The trial is registered with Clinicaltrials.gov, ID number NCT02819505.
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Affiliation(s)
- Rebecca Louise Jones
- Musculoskeletal Physiology Research Group, Sport, Health and Performance Enhancement (SHAPE) Research Centre, School of Science and Technology, Nottingham Trent University, Erasmus Darwin Building, Clifton Lane, Clifton, Nottingham, NG11 8NS, UK
| | - Cleveland Thomas Barnett
- Musculoskeletal Physiology Research Group, Sport, Health and Performance Enhancement (SHAPE) Research Centre, School of Science and Technology, Nottingham Trent University, Erasmus Darwin Building, Clifton Lane, Clifton, Nottingham, NG11 8NS, UK
| | - Joel Davidson
- Musculoskeletal Physiology Research Group, Sport, Health and Performance Enhancement (SHAPE) Research Centre, School of Science and Technology, Nottingham Trent University, Erasmus Darwin Building, Clifton Lane, Clifton, Nottingham, NG11 8NS, UK
| | - Billy Maritza
- Musculoskeletal Physiology Research Group, Sport, Health and Performance Enhancement (SHAPE) Research Centre, School of Science and Technology, Nottingham Trent University, Erasmus Darwin Building, Clifton Lane, Clifton, Nottingham, NG11 8NS, UK
| | - William D Fraser
- Norwich Medical School, University of East Anglia, Norwich, Norfolk, UK
- Norfolk and Norwich University Hospital, Norwich, Norfolk, UK
| | | | - Craig Sale
- Musculoskeletal Physiology Research Group, Sport, Health and Performance Enhancement (SHAPE) Research Centre, School of Science and Technology, Nottingham Trent University, Erasmus Darwin Building, Clifton Lane, Clifton, Nottingham, NG11 8NS, UK.
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Abstract
Understanding of the musculoskeletal system has evolved from the collection of individual phenomena in highly selected experimental preparations under highly controlled and often unphysiological conditions. At the systems level, it is now possible to construct complete and reasonably accurate models of the kinetics and energetics of realistic muscles and to combine them to understand the dynamics of complete musculoskeletal systems performing natural behaviors. At the reductionist level, it is possible to relate most of the individual phenomena to the anatomical structures and biochemical processes that account for them. Two large challenges remain. At a systems level, neuroscience must now account for how the nervous system learns to exploit the many complex features that evolution has incorporated into muscle and limb mechanics. At a reductionist level, medicine must now account for the many forms of pathology and disability that arise from the many diseases and injuries to which this highly evolved system is inevitably prone. © 2017 American Physiological Society. Compr Physiol 7:429-462, 2017.
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Affiliation(s)
| | - Gerald E Loeb
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA
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Neyroud D, Cheng AJ, Bourdillon N, Kayser B, Place N, Westerblad H. Muscle Fatigue Affects the Interpolated Twitch Technique When Assessed Using Electrically-Induced Contractions in Human and Rat Muscles. Front Physiol 2016; 7:252. [PMID: 27445844 PMCID: PMC4924481 DOI: 10.3389/fphys.2016.00252] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 06/10/2016] [Indexed: 11/13/2022] Open
Abstract
The interpolated twitch technique (ITT) is the gold standard to assess voluntary activation and central fatigue. Yet, its validity has been questioned. Here we studied how peripheral fatigue can affect the ITT. Repeated contractions at submaximal frequencies were produced by supramaximal electrical stimulations of the human adductor pollicis muscle in vivo and of isolated rat soleus fiber bundles; an extra stimulation pulse was given during contractions to induce a superimposed twitch. Human muscles fatigued by repeated 30-Hz stimulation trains (3 s on–1 s off) showed an ~80% reduction in the superimposed twitch force accompanied by a severely reduced EMG response (M-wave amplitude), which implies action potential failure. Subsequent experiments combined a less intense stimulation protocol (1.5 s on–3 s off) with ischemia to cause muscle fatigue, but which preserved M-wave amplitude. However, the superimposed twitch force still decreased markedly more than the potentiated twitch force; with ITT this would reflect increased “voluntary activation.” In contrast, the superimposed twitch force was relatively spared when a similar protocol was performed in rat soleus bundles. Force relaxation was slowed by >150% in fatigued human muscles, whereas it was unchanged in rat soleus bundles. Accordingly, results similar to those in the human muscle were obtained when relaxation was slowed by cooling the rat soleus muscles. In conclusion, our data demonstrate that muscle fatigue can confound the quantification of central fatigue using the ITT.
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Affiliation(s)
- Daria Neyroud
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of LausanneLausanne, Switzerland; Department of Physiology, Faculty of Biology and Medicine, University of LausanneLausanne, Switzerland
| | - Arthur J Cheng
- Department of Physiology and Pharmacology, Karolinska Institutet Stockholm, Sweden
| | - Nicolas Bourdillon
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of LausanneLausanne, Switzerland; Department of Physiology, Faculty of Biology and Medicine, University of LausanneLausanne, Switzerland
| | - Bengt Kayser
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of LausanneLausanne, Switzerland; Department of Physiology, Faculty of Biology and Medicine, University of LausanneLausanne, Switzerland
| | - Nicolas Place
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of LausanneLausanne, Switzerland; Department of Physiology, Faculty of Biology and Medicine, University of LausanneLausanne, Switzerland
| | - Håkan Westerblad
- Department of Physiology and Pharmacology, Karolinska Institutet Stockholm, Sweden
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15
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De Andrade PBM, Neff LA, Strosova MK, Arsenijevic D, Patthey-Vuadens O, Scapozza L, Montani JP, Ruegg UT, Dulloo AG, Dorchies OM. Caloric restriction induces energy-sparing alterations in skeletal muscle contraction, fiber composition and local thyroid hormone metabolism that persist during catch-up fat upon refeeding. Front Physiol 2015; 6:254. [PMID: 26441673 PMCID: PMC4584973 DOI: 10.3389/fphys.2015.00254] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2015] [Accepted: 08/28/2015] [Indexed: 11/18/2022] Open
Abstract
Weight regain after caloric restriction results in accelerated fat storage in adipose tissue. This catch-up fat phenomenon is postulated to result partly from suppressed skeletal muscle thermogenesis, but the underlying mechanisms are elusive. We investigated whether the reduced rate of skeletal muscle contraction-relaxation cycle that occurs after caloric restriction persists during weight recovery and could contribute to catch-up fat. Using a rat model of semistarvation-refeeding, in which fat recovery is driven by suppressed thermogenesis, we show that contraction and relaxation of leg muscles are slower after both semistarvation and refeeding. These effects are associated with (i) higher expression of muscle deiodinase type 3 (DIO3), which inactivates tri-iodothyronine (T3), and lower expression of T3-activating enzyme, deiodinase type 2 (DIO2), (ii) slower net formation of T3 from its T4 precursor in muscles, and (iii) accumulation of slow fibers at the expense of fast fibers. These semistarvation-induced changes persisted during recovery and correlated with impaired expression of transcription factors involved in slow-twitch muscle development. We conclude that diminished muscle thermogenesis following caloric restriction results from reduced muscle T3 levels, alteration in muscle-specific transcription factors, and fast-to-slow fiber shift causing slower contractility. These energy-sparing effects persist during weight recovery and contribute to catch-up fat.
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Affiliation(s)
- Paula B M De Andrade
- Department of Medicine, Physiology, University of Fribourg Fribourg, Switzerland
| | - Laurence A Neff
- Pharmaceutical Biochemistry, Geneva-Lausanne School of Pharmaceutical Sciences, University of Geneva, University of Lausanne Geneva, Switzerland
| | - Miriam K Strosova
- Pharmacology, Geneva-Lausanne School of Pharmaceutical Sciences, University of Geneva, University of Lausanne Geneva, Switzerland
| | - Denis Arsenijevic
- Department of Medicine, Physiology, University of Fribourg Fribourg, Switzerland
| | - Ophélie Patthey-Vuadens
- Pharmaceutical Biochemistry, Geneva-Lausanne School of Pharmaceutical Sciences, University of Geneva, University of Lausanne Geneva, Switzerland ; Pharmacology, Geneva-Lausanne School of Pharmaceutical Sciences, University of Geneva, University of Lausanne Geneva, Switzerland
| | - Leonardo Scapozza
- Pharmaceutical Biochemistry, Geneva-Lausanne School of Pharmaceutical Sciences, University of Geneva, University of Lausanne Geneva, Switzerland
| | - Jean-Pierre Montani
- Department of Medicine, Physiology, University of Fribourg Fribourg, Switzerland
| | - Urs T Ruegg
- Pharmacology, Geneva-Lausanne School of Pharmaceutical Sciences, University of Geneva, University of Lausanne Geneva, Switzerland
| | - Abdul G Dulloo
- Department of Medicine, Physiology, University of Fribourg Fribourg, Switzerland
| | - Olivier M Dorchies
- Pharmaceutical Biochemistry, Geneva-Lausanne School of Pharmaceutical Sciences, University of Geneva, University of Lausanne Geneva, Switzerland ; Pharmacology, Geneva-Lausanne School of Pharmaceutical Sciences, University of Geneva, University of Lausanne Geneva, Switzerland
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Rodríguez-Matoso D, Mantecón A, Barbosa-Almeida E, Valverde T, García-Manso JM, Rodríguez-Ruiz D. Mechanical response of knee muscles in high level bodyboarders during performance. REV BRAS MED ESPORTE 2015. [DOI: 10.1590/1517-86922015210201507] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
INTRODUCTION: bodyboarding is a kind of surfing that has been growing very rapidly over the last decade and has now developed into one of the fastest growing water sports in the world.OBJECTIVES: evaluate the effects of fatigue on rectus femoris RF, vastus lateralis VL and vastus medialis VM and biceps femoris BF and semitendinosus ST during a high-level bodyboard competition using tensiomyography TMG.METHODS: subjects were 11 highly experienced years of practice: 15, SD=4.65 male bodyboarders age: 28.17, SD=2.89, body weight: 74.83, SD=6.13kg; height: 179.25, SD=3.93cm; BMI: 23.29, SD=1.81 participating in the final of the 2010 Spanish championship.RESULTS: the fatigue is especially evident due to a decrease in the values of relaxation time Tr and sustain time Ts caused by the specific characteristics of waves, how the waves evolve and the type of manoeuvre executed in competition due to the wave characteristics. The maximum radial displacement Dm value increased slightly in all muscles analysed and normalised response speed Vrn was stable, with a tendency to improve as athletes adapted to the type of physical effort and the environmental conditions of the competition.CONCLUSIONS: the study shows that the fatigue in the extensor and flexor muscles of the knee occurs in response to the demands of competition.
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17
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Gago P, Marques MC, Marinho DA, Ekblom MM. Passive muscle length changes affect twitch potentiation in power athletes. Med Sci Sports Exerc 2014; 46:1334-42. [PMID: 24389516 DOI: 10.1249/mss.0000000000000245] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
INTRODUCTION A conditioning maximal voluntary muscle action (MVC) has been shown to induce postactivation potentiation, that is, improved contractile muscle properties, when muscles are contracted isometrically. It is still uncertain how the contractile properties are affected during ongoing muscle length changes. The purpose of this study was to investigate the effects of a 6-s conditioning MVC on twitch properties of the plantarflexors during ongoing muscle length changes. METHODS Peak twitch, rate of torque development, and rate of torque relaxation, rising time, and half relaxation time were measured from supramaximal twitches evoked in the plantarflexors of 11 highly trained athletes. Twitches were evoked before a 6-s MVC and subsequently on eight different occasions during a 10-min recovery for five different modes: fast lengthening, slow lengthening, isometric, fast shortening, and slow shortening of the plantarflexors. RESULTS The magnitude and the duration of effects from the conditioning MVC were significantly different between modes. Peak twitch, rate of torque development, and rate of torque relaxation significantly increased for all modes but more so for twitches evoked during fast and slow shortening as compared with lengthening. Rising time was reduced in the lengthening modes but slightly prolonged in the shortening modes. Half relaxation time was significantly reduced for all modes, except fast lengthening. CONCLUSIONS The findings show that the effects of a conditioning MVC on twitch contractile properties are dependent on direction and velocity of ongoing muscle length changes. This may imply that functional enhancements from a conditioning MVC might be expected to be greatest for concentric muscle actions but are still present in isometric and eccentric parts of a movement.
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Affiliation(s)
- Paulo Gago
- 1Sports Sciences Department, University of Beira Interior, Covilhã, PORTUGAL; 2Research Center for Sport, Health and Human Development, PORTUGAL; 3Biomechanics and Motor Control laboratory, Swedish School of Sport and Health Sciences, Stockholm, SWEDEN; and 4Department of Neuroscience, Karolinska Institutet, Stockholm, SWEDEN
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Hortemo KH, Munkvik M, Lunde PK, Sejersted OM. Multiple causes of fatigue during shortening contractions in rat slow twitch skeletal muscle. PLoS One 2013; 8:e71700. [PMID: 23977116 PMCID: PMC3745421 DOI: 10.1371/journal.pone.0071700] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 07/08/2013] [Indexed: 01/18/2023] Open
Abstract
Fatigue in muscles that shorten might have other causes than fatigue during isometric contractions, since both cross-bridge cycling and energy demand are different in the two exercise modes. While isometric contractions are extensively studied, the causes of fatigue in shortening contractions are poorly mapped. Here, we investigate fatigue mechanisms during shortening contractions in slow twitch skeletal muscle in near physiological conditions. Fatigue was induced in rat soleus muscles with maintained blood supply by in situ shortening contractions at 37°C. Muscles were stimulated repeatedly (1 s on/off at 30 Hz) for 15 min against a constant load, allowing the muscle to shorten and perform work. Fatigue and subsequent recovery was examined at 20 s, 100 s and 15 min exercise. The effects of prior exercise were investigated in a second exercise bout. Fatigue developed in three distinct phases. During the first 20 s the regulatory protein Myosin Light Chain-2 (slow isoform, MLC-2s) was rapidly dephosphorylated in parallel with reduced rate of force development and reduced shortening. In the second phase there was degradation of high-energy phosphates and accumulation of lactate, and these changes were related to slowing of muscle relengthening and relaxation, culminating at 100 s exercise. Slowing of relaxation was also associated with increased leak of calcium from the SR. During the third phase of exercise there was restoration of high-energy phosphates and elimination of lactate, and the slowing of relaxation disappeared, whereas dephosphorylation of MLC-2s and reduced shortening prevailed. Prior exercise improved relaxation parameters in a subsequent exercise bout, and we propose that this effect is a result of less accumulation of lactate due to more rapid onset of oxidative metabolism. The correlation between dephosphorylation of MLC-2s and reduced shortening was confirmed in various experimental settings, and we suggest MLC-2s as an important regulator of muscle shortening.
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Affiliation(s)
- Kristin Halvorsen Hortemo
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- KG Jebsen Cardiac Research Centre and Centre for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Morten Munkvik
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- KG Jebsen Cardiac Research Centre and Centre for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Per Kristian Lunde
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- KG Jebsen Cardiac Research Centre and Centre for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Ole M. Sejersted
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- KG Jebsen Cardiac Research Centre and Centre for Heart Failure Research, University of Oslo, Oslo, Norway
- * E-mail:
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Katz A, Hernández A, Caballero DMR, Briceno JFB, Amezquita LVR, Kosterina N, Bruton JD, Westerblad H. Effects of N-acetylcysteine on isolated mouse skeletal muscle: contractile properties, temperature dependence, and metabolism. Pflugers Arch 2013; 466:577-85. [PMID: 23912895 DOI: 10.1007/s00424-013-1331-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 07/18/2013] [Accepted: 07/18/2013] [Indexed: 02/08/2023]
Abstract
The effects of the general antioxidant N-acetylcysteine (NAC) on muscle function and metabolism were examined. Isolated paired mouse extensor digitorum longus muscles were studied in the absence or presence of 20 mM NAC. Muscles were electrically stimulated to perform 100 isometric tetanic contractions (300 ms duration) at frequencies resulting in ∼85% of maximal force (70-150 Hz at 25-40 °C). NAC did not significantly affect peak force in the unfatigued state at any temperature but significantly slowed tetanic force development in a temperature-dependent fashion (e.g., time to 50% of peak tension averaged 35 ± 2 ms [control] and 37 ± 1 ms [NAC] at 25 °C vs. 21 ± 1 ms [control] and 52 ± 6 ms [NAC, P < 0.01] at 40 °C). During repeated contractions, NAC maximally enhanced peak force by the fifth tetanus at all temperatures (by ∼30%). Thereafter, the effect of NAC disappeared rapidly at high temperatures (35-40 °C) and more slowly at the lower temperatures (25-30 °C). At all temperatures, the enhancing effect of NAC on peak force was associated with a slowing of relaxation. NAC did not significantly affect myosin light chain phosphorylation at rest or after five contractions (∼50% increase vs. rest). After five tetani, lactate and inorganic phosphate increased about 20-fold and 2-fold, respectively, both in control and NAC-treated muscles. Interestingly, after five tetani, the increase in glucose 6-P was ∼2-fold greater, whereas the increase in malate was inhibited by ∼75% with NAC vs. control, illustrating the metabolic effects of NAC. NAC slightly decreased the maximum shortening velocity in early fatigue (five to seven repeated tetani). These data demonstrate that the antioxidant NAC transiently enhances muscle force generation by a mechanism that is independent of changes in myosin light chain phosphorylation and inorganic phosphate. The slowing of relaxation suggests that NAC enhances isometric force by facilitating fusion (i.e., delaying force decline between pulses). The initial slowing of tension development and subsequent slowing of relaxation suggest that NAC would result in impaired performance during a high-intensity dynamic exercise.
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Affiliation(s)
- Abram Katz
- Department of Physiology and Pharmacology, Karolinska Institutet, 17177, Stockholm, Sweden,
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Cheng AJ, Rice CL. Factors contributing to the fatigue-related reduction in active dorsiflexion joint range of motion. Appl Physiol Nutr Metab 2013; 38:490-7. [DOI: 10.1139/apnm-2012-0357] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Reductions in active joint range of motion (ROM) are responsible for decreased work-generating capacity during fatiguing repetitive isotonic shortening contractions. Factors responsible for impairing the joint-angle-specific net torque developed during muscle shortening could include fatigue-induced torque loss, shortening-induced torque depression in the agonist muscle, and opposing passive tension of the antagonists, but these have not been systematically explored. Nine men (aged 25.8 ± 2.0 years) performed a maximal-effort fatiguing task that consisted of repetitive loaded shortening dorsiflexions through a 40° ankle joint ROM until active ROM decreased by 50%. Torque developed during contractile shortening, as well as passive opposing tension, was quantified before and after the reduction in active ROM. Before fatigue, and compared with maximum voluntary isometric contraction torque at the terminal ROM, shortening-induced torque depression in the agonist muscle and passive tension from the antagonists reduced net torque developed at the end of contractile shortening by ∼42% and ∼19%, respectively. After fatigue, a steepened ascending joint torque–angle relationship remained during contractile shortening, but neither muscle coactivation nor contractile slowing contributed to the fatigue-induced torque loss. Fatigue-induced torque loss, shortening-induced torque depression in the agonist, and passive tension in the antagonist greatly depressed net torque developed at the end of contractile shortening. These contributed to the fatigue-induced reduction in active ROM by impairing the ability of the dorsiflexors to generate sufficient torque to overcome the imposed load at the end of contractile shortening.
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Affiliation(s)
- Arthur J. Cheng
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON N6A 5B9, Canada
| | - Charles L. Rice
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, and Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, N6A 5B9 Canada
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Intense resistance exercise induces early and transient increases in ryanodine receptor 1 phosphorylation in human skeletal muscle. PLoS One 2012; 7:e49326. [PMID: 23173055 PMCID: PMC3500289 DOI: 10.1371/journal.pone.0049326] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2012] [Accepted: 10/10/2012] [Indexed: 12/22/2022] Open
Abstract
Background While ryanodine receptor 1 (RyR1) critically contributes to skeletal muscle contraction abilities by mediating Ca2+ion oscillation between sarcoplasmatic and myofibrillar compartments, AMP-activated protein kinase (AMPK) senses contraction-induced energetic stress by phosphorylation at Thr172. Phosphorylation of RyR1 at serine2843 (pRyR1Ser2843) results in leaky RyR1 channels and impaired Ca2+homeostasis. Because acute resistance exercise exerts decreased contraction performance in skeletal muscle, preceded by high rates of Ca2+-oscillation and energetic stress, intense myofiber contractions may induce increased RyR1 and AMPK phosphorylation. However, no data are available regarding the time-course and magnitude of early RyR1 and AMPK phosphorylation in human myofibers in response to acute resistance exercise. Purpose Determine the effects and early time-course of resistance exercise on pRyR1Ser2843 and pAMPKThr172 in type I and II myofibers. Methods 7 male subjects (age 23±2 years, height: 185±7 cm, weight: 82±5 kg) performed 3 sets of 8 repetitions of maximum eccentric knee extensions. Muscle biopsies were taken at rest, 15, 30 and 60 min post exercise. pRyR1Ser2843 and pAMPKThr172 levels were determined by western blot and semi-quantitative immunohistochemistry techniques. Results While total RyR1 and total AMPK levels remained unchanged, RyR1 was significantly more abundant in type II than type I myofibers. pRyR1Ser2843 increased 15 min and peaked 30 min (p<0.01) post exercise in both myofiber types. Type I fibers showed relatively higher increases in pRyR1Ser2843 levels than type II myofibers and remained elevated up to 60 min post resistance exercise (p<0.05). pAMPKThr172 also increased 15 to 30 min post exercise (p<0.01) in type I and II myofibers and in whole skeletal muscle. Conclusion Resistance exercise induces acutely increased pRyR1Ser2843 and concomitantly pAMPKThr172 levels for up to 30 min in resistance exercised myofibers. This provides a time-course by which pRyR1Ser2843 can mechanistically impact Ca2+handling properties and consequently induce reduced myofiber contractility beyond immediate fatiguing mechanisms.
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Maximal voluntary contraction force, SR function and glycogen resynthesis during the first 72 h after a high-level competitive soccer game. Eur J Appl Physiol 2011; 111:2987-95. [PMID: 21448723 DOI: 10.1007/s00421-011-1919-y] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Accepted: 03/08/2011] [Indexed: 10/18/2022]
Abstract
The aim of this study was to examine maximal voluntary knee-extensor contraction force (MVC force), sarcoplasmic reticulum (SR) function and muscle glycogen levels in the days after a high-level soccer game when players ingested an optimised diet. Seven high-level male soccer players had a vastus lateralis muscle biopsy and a blood sample collected in a control situation and at 0, 24, 48 and 72 h after a competitive soccer game. MVC force, SR function, muscle glycogen, muscle soreness and plasma myoglobin were measured. MVC force sustained over 1 s was 11 and 10% lower (P < 0.05) after 0 and 24 h, respectively, compared with control. The rate of SR Ca(2+) uptake at 800 nM [Ca(2+)](free) was lower (P < 0.05) after 0 h (2.5 μmol Ca(2+) g prot(-1) min(-1)) than for all other time points (24 h: 5.1 μmol Ca(2+) g prot(-1) min(-1)). However, SR Ca(2+) release rate was not affected. Plasma myoglobin was sixfold higher (P < 0.05) immediately after the game, but normalised 24 h after the game. Quadriceps muscle soreness (0-10 VAS-scale) was higher (P < 0.05) after 0 h (3.6), 24 h (1.8), 48 h (1.1) and 72 h (1.4) compared with control (0.1). Muscle glycogen was 57 and 27% lower (P < 0.001) 0 and 24 h after the game compared with control (193 and 328 vs. 449 mmol kg d w(-1)). In conclusion, maximal voluntary contraction force and SR Ca(2+) uptake were impaired and muscle soreness was elevated after a high-level soccer game, with faster recovery of SR function in comparison with MVC force, soreness and muscle glycogen.
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Ereline J, Gapeyeva H, Pääsuke M. Comparison of twitch contractile properties of plantarflexor muscles in Nordic combined athletes, cross-country skiers, and sedentary men. Eur J Sport Sci 2011. [DOI: 10.1080/17461391.2010.481335] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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24
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Place N, Yamada T, Bruton JD, Westerblad H. Muscle fatigue: from observations in humans to underlying mechanisms studied in intact single muscle fibres. Eur J Appl Physiol 2010; 110:1-15. [DOI: 10.1007/s00421-010-1480-0] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/07/2010] [Indexed: 01/01/2023]
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The influence of muscle length on the fatigue-related reduction in joint range of motion of the human dorsiflexors. Eur J Appl Physiol 2010; 109:405-15. [DOI: 10.1007/s00421-010-1364-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/13/2010] [Indexed: 10/19/2022]
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26
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Zanou N, Shapovalov G, Louis M, Tajeddine N, Gallo C, Van Schoor M, Anguish I, Cao ML, Schakman O, Dietrich A, Lebacq J, Ruegg U, Roulet E, Birnbaumer L, Gailly P. Role of TRPC1 channel in skeletal muscle function. Am J Physiol Cell Physiol 2010; 298:C149-62. [PMID: 19846750 PMCID: PMC2806157 DOI: 10.1152/ajpcell.00241.2009] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Accepted: 10/19/2009] [Indexed: 11/22/2022]
Abstract
Skeletal muscle contraction is reputed not to depend on extracellular Ca2+. Indeed, stricto sensu, excitation-contraction coupling does not necessitate entry of Ca2+. However, we previously observed that, during sustained activity (repeated contractions), entry of Ca2+ is needed to maintain force production. In the present study, we evaluated the possible involvement of the canonical transient receptor potential (TRPC)1 ion channel in this entry of Ca2+ and investigated its possible role in muscle function. Patch-clamp experiments reveal the presence of a small-conductance channel (13 pS) that is completely lost in adult fibers from TRPC1(-/-) mice. The influx of Ca2+ through TRPC1 channels represents a minor part of the entry of Ca(2+) into muscle fibers at rest, and the activity of the channel is not store dependent. The lack of TRPC1 does not affect intracellular Ca2+ concentration ([Ca2+](i)) transients reached during a single isometric contraction. However, the involvement of TRPC1-related Ca2+ entry is clearly emphasized in muscle fatigue. Indeed, muscles from TRPC1(-/-) mice stimulated repeatedly progressively display lower [Ca2+](i) transients than those observed in TRPC1(+/+) fibers, and they also present an accentuated progressive loss of force. Interestingly, muscles from TRPC1(-/-) mice display a smaller fiber cross-sectional area, generate less force per cross-sectional area, and contain less myofibrillar proteins than their controls. They do not present other signs of myopathy. In agreement with in vitro experiments, TRPC1(-/-) mice present an important decrease of endurance of physical activity. We conclude that TRPC1 ion channels modulate the entry of Ca(2+) during repeated contractions and help muscles to maintain their force during sustained repeated contractions.
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Affiliation(s)
- Nadège Zanou
- Laboratory of Cell Physiology, Inst. of Neuroscience, Université Catholique de Louvain, 55/40 av. Hippocrate, 1200 Brussels, Belgium.
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LEE SAMUELCK, DING JUN, PROSSER LAURAA, WEXLER ANTHONYS, BINDER-MACLEOD STUARTA. A predictive mathematical model of muscle forces for children with cerebral palsy. Dev Med Child Neurol 2009; 51:949-58. [PMID: 19703211 PMCID: PMC7935412 DOI: 10.1111/j.1469-8749.2009.03350.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIM The purpose of this study was to determine if our previously developed muscle model could be used to predict forces of the quadriceps femoris and triceps surae muscles of children with spastic diplegic cerebral palsy (CP). METHOD Twenty-two children with CP (12 males, 10 females; mean age 10y, SD 2y, range 7-13y; Gross Motor Function Classification System levels II and III) participated. A physiologically based mathematical model with four free parameters is presented. RESULTS For individuals with CP, the model predicted well the force profile throughout each contraction and both peak force and force-time integral responses to a wide range of stimulation frequencies (5-100Hz) and different stimulation patterns (constant-, variable-, and doublet-frequency trains) both for nonfatigued and fatigued muscles. INTERPRETATION The significance of this work is the insight the model can provide into the physiology of muscle in CP. Additionally, the model can potentially be applied clinically to design optimal electrical stimulation patterns for interventions to address impairments in strength and function in individuals with CP, such as functional electrical stimulation-assisted cycling.
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Affiliation(s)
- SAMUEL C K LEE
- Department of Physical Therapy, University of Delaware, Newark, DE, USA.,Research Department, Shriners Hospitals for Children, Philadelphia, PA 19140, USA
| | - JUN DING
- Department of Physical Therapy, University of Delaware, Newark, DE, USA
| | - LAURA A PROSSER
- Department of Physical Therapy, University of Delaware, Newark, DE, USA.,Research Department, Shriners Hospitals for Children, Philadelphia, PA 19140, USA
| | - ANTHONY S WEXLER
- Departments of Mechanical and Aeronautical Engineering, Civil and Environmental Engineering, and Land and Water resources, University of California, Davis, CA, USA
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Choi SJ, Widrick JJ. Combined effects of fatigue and eccentric damage on muscle power. J Appl Physiol (1985) 2009; 107:1156-64. [PMID: 19661451 DOI: 10.1152/japplphysiol.00403.2009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Many physical activities can induce both transient and long-lasting muscle dysfunction. The separate and interactive effects of short-term fatigue and long-lasting contraction-induced damage were evaluated in an in vitro mouse soleus preparation (35 degrees C) using the work loop technique. Repetitive fatiguing work loops reduced positive work (work produced by the muscle), increased negative work (work required to reextend the muscle), and reduced cyclical power (net work/time) immediately after treatment. These changes were readily reversible. The fatigue treatment had no long-term effects on optimal muscle length (L(o)) and isometric force (P(o)). High strain lengthening work loops, where the muscle contracted eccentrically, resulted in both immediate and long-lasting positive work, power, and P(o) deficits as well as a shift in L(o) to longer lengths. When the treatments were combined, i.e., fatigued muscles subjected to eccentric activity, the immediate power deficit exceeded the sum of the power deficits noted for the other two treatments. Much of this effect was due to an exaggerated rise in negative work. However, in the long term, power and P(o) deficits and the shift in L(o) were reduced compared with the damage-only treatment. These results show that 1) the immediate effects of combined fatigue and damage on cyclical power are synergistic, in large part because of a reduced ability of the muscle to relax; and 2) fatigued muscles are less susceptible to long-term contraction-induced dysfunction. Fatigue may protect against long-term damage by reducing the probability that sarcomeres are lengthened beyond myofilament overlap.
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Affiliation(s)
- Seung Jun Choi
- Dept. of Physical Medicine and Rehabilitation, Harvard Medical School, and Spaulding Rehabilitation Hospital, 125 Nashua St., Boston, MA 02114, USA
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Jones DA, Turner DL, McIntyre DB, Newham DJ. Energy turnover in relation to slowing of contractile properties during fatiguing contractions of the human anterior tibialis muscle. J Physiol 2009; 587:4329-38. [PMID: 19596896 DOI: 10.1113/jphysiol.2009.175265] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Slowing and loss of muscle power are major factors limiting physical performance but little is known about the molecular mechanisms involved. The slowing might be a consequence of slow detachment of cross bridges and, if this were the case, then a reduction in the ATP cost of an isometric contraction would be expected as the muscle fatigued. The human anterior tibialis muscle was stimulated repeatedly under ischaemic conditions at 50 Hz for 1.6 s with a 50% duty cycle and muscle metabolites measured by (31)P magnetic resonance spectroscopy. Over the course of 20 contractions the half-time of relaxation increased from 36.5 +/- 0.09 ms (mean +/- s.e.m.) to 113 +/- 17 ms and isometric force was reduced to 63 +/- 3% of the initial value. ATP turnover was determined from the change in high energy phosphates and lactate production, the latter estimated from the change of intracellular pH. ATP turnover over the first three contractions was 2.45 +/- 0.09 mM s(1) and decreased to 1.8 +/- 0.06 mm s(1) over the last five tetani. However, when this latter value was normalised for the decrease in isometric force, it became 2.56 +/- 0.3 mM s(1), which is the same as the turnover of the fresh muscle. The data suggest that the rate of cross bridge detachment is unaffected by fatigue and are consistent the suggestion that it is the rate of attachment which is slowed rather than the rate of detachment. The present results focus attention on stages in the cross bridge cycle concerned with attachment and the transition from low to high force states that may be influenced by metabolic changes in the fatiguing muscle.
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Affiliation(s)
- David A Jones
- School of Sport and Exercise Sciences, University of Birmingham, Birmingham B15 2TT, UK.
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Abstract
During exercise, fatigue is defined as a reversible reduction in force- or power-generating capacity and can be elicited by “central” and/or “peripheral” mechanisms. During skeletal muscle contractions, both aspects of fatigue may develop independent of alterations in convective O2delivery; however, reductions in O2supply exacerbate and increases attenuate the rate of accumulation. In this regard, peripheral fatigue development is mediated via the O2-dependent rate of accumulation of metabolic by-products (e.g., inorganic phosphate) and their interference with excitation-contraction coupling within the myocyte. In contrast, the development of O2-dependent central fatigue is elicited 1) by interference with the development of central command and/or 2) via inhibitory feedback on central motor drive secondary to the peripheral effects of low convective O2transport. Changes in convective O2delivery in the healthy human can result from modifications in arterial O2content, blood flow, or a combination of both, and they can be induced via heavy exercise even at sea level; these changes are exacerbated during acute and chronic exposure to altitude. This review focuses on the effects of changes in convective O2delivery on the development of central and peripheral fatigue.
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Abstract
Fatigue of skeletal muscle involves many systems beginning with the central nervous system and ending with the contractile machinery. This review concentrates on those factors that directly affect the actomyosin interaction: the build-up of metabolites; myosin phosphorylation; and oxidation of the myofibrillar proteins by free radicals. The decrease in [ATP] and increase in [ADP] appear to play little role in modulating function. The increase in phosphate inhibits tension. The decrease in pH, long thought to be a major factor, is now known to play a more minor role. Myosin phosphorylation potentiates the force achieved in a twitch, and a further role in inhibiting velocity is proposed. Protein oxidation can both potentiate and inhibit the actomyosin interaction. It is concluded that these factors, taken together, do not fully explain the inhibition of the actomyosin interaction observed in living fibers, and thus additional modulators of this interaction remain to be discovered.
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Affiliation(s)
- Roger Cooke
- Department of Biochemistry and Biophysics and Cardiovascular Research Institute, University of California, San Francisco, California 94158-2517, USA.
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Abstract
Impaired calcium release from the sarcoplasmic reticulum (SR) has been identified as a contributor to fatigue in isolated skeletal muscle fibers. The functional importance of this phenomenon can be quantified by the use of agents, such as caffeine, which can increase SR Ca2+release during fatigue. A number of possible mechanisms for impaired calcium release have been proposed. These include reduction in the amplitude of the action potential, potentially caused by extracellular K+accumulation, which may reduce voltage sensor activation but is counteracted by a number of mechanisms in intact animals. Reduced effectiveness of SR Ca2+channel opening is caused by the fall in intracellular ATP and the rise in Mg2+concentrations that occur during fatigue. Reduced Ca2+available for release within the SR can occur if inorganic phosphate enters the SR and precipitates with Ca2+. Further progress requires the development of methods that can identify impaired SR Ca2+release in intact, blood-perfused muscles and that can distinguish between the various mechanisms proposed.
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Abstract
Repeated, intense use of muscles leads to a decline in performance known as muscle fatigue. Many muscle properties change during fatigue including the action potential, extracellular and intracellular ions, and many intracellular metabolites. A range of mechanisms have been identified that contribute to the decline of performance. The traditional explanation, accumulation of intracellular lactate and hydrogen ions causing impaired function of the contractile proteins, is probably of limited importance in mammals. Alternative explanations that will be considered are the effects of ionic changes on the action potential, failure of SR Ca2+release by various mechanisms, and the effects of reactive oxygen species. Many different activities lead to fatigue, and an important challenge is to identify the various mechanisms that contribute under different circumstances. Most of the mechanistic studies of fatigue are on isolated animal tissues, and another major challenge is to use the knowledge generated in these studies to identify the mechanisms of fatigue in intact animals and particularly in human diseases.
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Guo R, Li SB, Zhao LN, Zhao YS, Lu W, Yuan P, Deng P, Liao F. A new linearly-combined bi-exponential model for kinetic analysis of the isometric relaxation process of Bufo gastrocnemius under electric stimulation in vitro. J Zhejiang Univ Sci B 2007; 8:867-74. [PMID: 18257119 PMCID: PMC2100157 DOI: 10.1631/jzus.2007.b0867] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2007] [Accepted: 10/22/2007] [Indexed: 11/11/2022]
Abstract
There was a slow-relaxing tail of skeletal muscles in vitro upon the inhibition of Ca(2+)-pump by cyclopiazonic acid (CPA). Herein, a new linearly-combined bi-exponential model to resolve this slow-relaxing tail from the fast-relaxing phase was investigated for kinetic analysis of the isometric relaxation process of Bufo gastrocnemius in vitro, in comparison to the single exponential model and the classical bi-exponential model. During repetitive stimulations at a 2-s interval by square pulses of a 2-ms duration at 12 V direct currency (DC), the isometric tension of Bufo gastrocnemius was recorded at 100 Hz. The relaxation curve with tensions falling from 90% of the peak to the 15th datum before next stimulation was analyzed by three exponential models using a program in MATLAB 6.5. Both the goodness of fit and the distribution of the residuals for the best fitting supported the comparable validity of this new bi-exponential model for kinetic analysis of the relaxation process of the control muscles. After CPA treatment, however, this new bi-exponential model showed an obvious statistical superiority for kinetic analysis of the muscle relaxation process, and it gave the estimated rest tension consistent to that by experimentation, whereas both the classical bi-exponential model and the single exponential model gave biased rest tensions. Moreover, after the treatment of muscles by CPA, both the single exponential model and the classical bi-exponential model yielded lowered relaxation rates, nevertheless, this new bi-exponential model had relaxation rates of negligible changes except much higher rest tensions. These results suggest that this novel linearly-combined bi-exponential model is desirable for kinetic analysis of the relaxation process of muscles with altered Ca(2+)-pumping activity.
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Tammik K, Matlep M, Ereline J, Gapeyeva H, Pääsuke M. Muscle contractile properties in children with spastic diplegia. Brain Dev 2007; 29:553-8. [PMID: 17418991 DOI: 10.1016/j.braindev.2007.02.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2006] [Revised: 02/10/2007] [Accepted: 02/17/2007] [Indexed: 10/23/2022]
Abstract
The aim of the present study was to evaluate contractile properties of the plantarflexor muscles in children with spastic diplegia (SD) in comparison of age-matched healthy children. Twelve prepubertal children with SD aged 11-12 years (6 girls and 6 boys) and 12 age- and gender-matched healthy control children (6 girls and 6 boys) participated in this study. Subjects were seated in a custom-made dynamometric chair with the dominant leg flexed 90 degrees at the knee and ankle joints. Twitch contraction characteristics of the plantarflexor muscles were measured by supramaximal electrical stimulation of posterior tibial nerve in popliteal fossa using square-wave pulses of 1 ms duration at rest and after a brief (5 s) isometric maximal voluntary contraction (MVC), i.e., during post-activation potentiation (PAP). Children with SD had significantly lower (p<0.05) MVC force, twitch contraction peak force (PF), PAP of twitch force, and twitch maximal rates of force development and relaxation compared to control group. Twitch contraction PF:MVC force ratio was higher (p<0.05) in children with SD than in the control group. However, no significant differences in twitch contraction and half-relaxation times were observed between the measured groups. It was concluded that prepubertal children with SD in comparison of normal children are characterized by markedly reduced isometric voluntary and electrically evoked twitch contraction maximal force, capacity for twitch PAP, and rates of twitch force production and relaxation of the plantarflexor muscles. The time-course characteristics of isometric twitch contraction were similar in children with SD and normal children.
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Affiliation(s)
- Karin Tammik
- Institute of Exercise Biology and Physiotherapy, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Estonia
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Pääsuke M, Saapar L, Ereline J, Gapeyeva H, Requena B, Oöpik V. Postactivation potentiation of knee extensor muscles in power- and endurance-trained, and untrained women. Eur J Appl Physiol 2007; 101:577-85. [PMID: 17674025 DOI: 10.1007/s00421-007-0532-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/09/2007] [Indexed: 11/26/2022]
Abstract
This study compared postactivation potentiation (PAP) in knee extensor muscles after a 10 s conditioning isometric maximal voluntary contraction (MVC) in female power- (PT, n=12) and endurance-trained (ET, n=12) athletes, and untrained (UT, n=12) women aged 20-24 years. Isometric twitch characteristics of the knee extensor muscles were assessed in pre-MVC condition and during 15 min post-MVC period using supramaximal electrical stimulation of the femoral nerve by rectangular pulses of 1 ms duration. A significant (P<0.05) potentiation of twitch peak torque (Pt, 30-51% in different groups), maximal rates of torque development (50-125%) and relaxation (76-124%) occurred immediately (2 s) post-MVC. PAP declined sharply at 1-3 min of recovery, whereas a significant potentiation of twitch Pt was still present for ET athletes at 1 min, and for UT women and PT athletes at 5 min of recovery, respectively. There were no significant (P>0.05) changes in twitch contraction and half-relaxation times after a 10 s conditioning MVC. We concluded that PAP in knee extensor muscles is enhanced in PT but not in ET female athletes. The magnitude of PAP was greater when measured immediately after the conditioning MVC and its decline was slower in PT compared with ET athletes. Immediately post-MVC, twitch speed-related characteristics were potentiated to a greater extent than twitch Pt. The time-course of isometric twitch was not significantly altered by conditioning MVC.
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Affiliation(s)
- Mati Pääsuke
- Institute of Exercise Biology and Physiotherapy, University of Tartu, 5 Jakobi Street, 51014, Tartu, Estonia.
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Clark BC, Cook SB, Ploutz-Snyder LL. Reliability of techniques to assess human neuromuscular function in vivo. J Electromyogr Kinesiol 2007; 17:90-101. [PMID: 16427317 DOI: 10.1016/j.jelekin.2005.11.008] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2005] [Revised: 11/21/2005] [Accepted: 11/28/2005] [Indexed: 11/20/2022] Open
Abstract
The purpose of this study was to comprehensively evaluate the reliability of a large number of commonly utilized experimental tests of in vivo human neuromuscular function separated by 4-weeks. Numerous electrophysiological parameters (i.e., voluntary and evoked electromyogram [EMG] signals), contractile properties (i.e., evoked forces and rates of force development and relaxation), muscle morphology (i.e., MRI-derived cross-sectional area [CSA]) and performance tasks (i.e., steadiness and time to task failure) were assessed from the plantarflexor muscle group in 17 subjects before and following 4-weeks where they maintained their normal lifestyle. The reliability of the measured variables had wide-ranging levels of consistency, with coefficient of variations (CV) ranging from approximately 2% to 20%, and intraclass correlation coefficients (ICC) between 0.53 and 0.99. Overall, we observed moderate to high-levels of reliability in the vast majority of the variables we assessed (24 out of the 29 had ICC>0.70 and CV<15%). The variables demonstrating the highest reliability were: CSA (ICC=0.93-0.98), strength (ICC=0.97), an index of nerve conduction velocity (ICC=0.95), and H-reflex amplitude (ICC=0.93). Conversely, the variables demonstrating the lowest reliability were: the amplitude of voluntary EMG signal (ICC=0.53-0.88), and the time to task failure of a sustained submaximal contraction (ICC=0.64). Additionally, relatively little systematic bias (calculated through the limits of agreement) was observed in these measures over the repeat sessions. In conclusion, while the reliability differed between the various measures, in general it was rather high even when the testing sessions are separated by a relatively long duration of time.
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Affiliation(s)
- Brian C Clark
- Musculoskeletal Research Laboratory, Department of Exercise Science, Syracuse University, 820 Comstock Avenue, Room 201, Syracuse, NY 13244, USA.
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Kuu S, Gapeyeva H, Ereline J, Pääsuke M. Twitch contractile properties of plantarflexor muscles in young and middle-aged recreationally physically active and non-active women. Aging Clin Exp Res 2007; 19:48-54. [PMID: 17332721 DOI: 10.1007/bf03325210] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
BACKGROUND AND AIMS This study examined the effect of recreational physical activity on the contractile properties of skeletal muscles in middle-aged vs young women. METHODS A total 74 young (20-29-year-old) and middle-aged (45-54-year-old) women participated. The subjects were distributed into four groups: 1) young recreationally physically active (RPA) (n=19), 2) young recreationally physically non-active (RPN) (n=21), 3) middle-aged RPA (n=23) and 4) middle- aged RPN (n=16). RPA women exercised regularly in groups of recreational gymnastics 2-3 times per week. Isometric twitch of the plantarflexor muscles was evoked by supramaximal electrical stimulation of the tibial nerve in resting and post-activation potentiation state. RESULTS A greater resting twitch maximal rate of force development (RFD), and potentiated twitch peak force (PF) and maximal rate of relaxation (RR) were observed in the young RPA women compared with the two middle-aged women groups. In young RPN women, these characteristics were greater than in the middle-aged RPN women, whereas they did not differ significantly when compared with the middle-aged RPA women. A shorter resting and potentiated twitch contraction time, and a greater potentiated twitch maximal RFD were found in the young compared with the middle-aged groups. There were no significant differences in twitch characteristics between RPA and RPN women of similar age. CONCLUSIONS The recreational gymnastic type of physical activity did not have a marked effect on twitch contractile properties in young and middle-aged women. A reduced speed of isometric twitch contraction was found in middle-aged women, which was more pronounced in the post-activation potentiation state.
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Affiliation(s)
- Saima Kuu
- Institute of Exercise Biology and Physiotherapy, Centre of Behavioural and Health Sciences, University of Tartu, Jakobi 5, Tartu 51014, Estonia.
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Clark BC, Fernhall B, Ploutz-Snyder LL. Adaptations in human neuromuscular function following prolonged unweighting: I. Skeletal muscle contractile properties and applied ischemia efficacy. J Appl Physiol (1985) 2006; 101:256-63. [PMID: 16514004 DOI: 10.1152/japplphysiol.01402.2005] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Strength loss following disuse may result from alterations in muscle and/or neurological properties. In this paper, we report our findings on human plantar flexor muscle properties following 4 wk of limb suspension (unilateral lower limb suspension), along with the effect of applied ischemia (Isc) on these properties. In the companion paper (Part II), we report our findings on the changes in neurological properties. Measurements of voluntary and evoked forces, the compound muscle fiber action potential (CMAP), and muscle cross-sectional area (CSA) were collected before and after 4 wk of unilateral lower limb suspension in adults (n = 18; 19-28 yr). A subset of subjects (n = 6) received applications of Isc 3 days/wk (3 sets; 5-min duration). In the subjects not receiving Isc, the loss in CSA and strength was as expected ( approximately 9 and 14%). We observed a 30% slowing in the duration of the CMAP, a 10% decrease in evoked doublet force, a 12% increase in the twitch-to-doublet force ratio, and an altered postactivation potentiation response (11% increase in the postactivation potentiation-to-doublet ratio). We also detected a 10% slowing in the ability of the plantar flexor to develop force during the initial phase of an evoked contraction, along with a 6% reduction in in vivo specific doublet force. In the Isc subjects, no preservation was observed in strength or the evoked muscle properties. However, the Isc group did maintain CSA of the lateral gastrocnemius, as the control subjects' lateral gastrocnemius atrophied 10.2%, whereas the subjects receiving Isc atrophied 4.7%. Additionally, Isc abolished the unweighting-induced slowing in the CMAP. These findings suggest that unweighting alters the contractile properties involved in the excitation-contraction coupling processes and that Isc impacts the sarcolemma.
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Affiliation(s)
- Brian C Clark
- Musculoskeletal Research Laboratory, Department of Exercise Science, Syracuse University, New York, USA.
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Zhang SJ, Andersson DC, Sandström ME, Westerblad H, Katz A. Cross bridges account for only 20% of total ATP consumption during submaximal isometric contraction in mouse fast-twitch skeletal muscle. Am J Physiol Cell Physiol 2006; 291:C147-54. [PMID: 16481370 DOI: 10.1152/ajpcell.00578.2005] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is generally believed that cross bridges account for >50% of the total ATP consumed by skeletal muscle during contraction. We investigated the effect of N-benzyl-p-toluene sulfonamide (BTS), an inhibitor of myosin ATPase, on muscle force production and energy metabolism under near-physiological conditions (50-Hz stimulation frequency at 30 degrees C results in 35% of maximal force). Extensor digitorum longus muscles from mice were isolated and stimulated to perform continuous isometric tetanic contractions. Metabolites of energy metabolism were analyzed with fluorometric techniques. ATP turnover was estimated from the changes in phosphocreatine (PCr), ATP, and lactate (-2DeltaATP - DeltaPCr + [1.5Deltalactate]). During contractions (2-10 s), BTS decreased force production to approximately 5% of control. Under these conditions, BTS inhibited ATP turnover by only 18-25%. ATP turnover decreased markedly and similarly with and without BTS as the duration of contraction progressed. In conclusion, cross bridges (i.e., actomyosin ATPase) account for only a small fraction (approximately 20%) of the ATP consumption during contraction in mouse fast-twitch skeletal muscle under near-physiological conditions, suggesting that ion pumping is the major energy-consuming process.
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Affiliation(s)
- Shi-Jin Zhang
- Department of Physiology and Pharmacology, Karolinska Institutet, Von Eulers väg 8, 171 77 Stockholm, Sweden
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Ursu D, Schuhmeier RP, Melzer W. Voltage-controlled Ca2+ release and entry flux in isolated adult muscle fibres of the mouse. J Physiol 2004; 562:347-65. [PMID: 15528246 PMCID: PMC1665514 DOI: 10.1113/jphysiol.2004.073882] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The voltage-activated fluxes of Ca(2+) from the sarcoplasmic reticulum (SR) and from the extracellular space were studied in skeletal muscle fibres of adult mice. Single fibres of the interosseus muscle were enzymatically isolated and voltage clamped using a two-electrode technique. The fibres were perfused from the current-passing micropipette with a solution containing 15 mm EGTA and 0.2 mm of either fura-2 or the faster, lower affinity indicator fura-FF. Electrical recordings in parallel with the fluorescence measurements allowed the estimation of intramembrane gating charge movements and transmembrane Ca(2+) inward current exhibiting half-maximal activation at -7.60 +/- 1.29 and 3.0 +/- 1.44 mV, respectively. The rate of Ca(2+) release from the SR was calculated after fitting the relaxation phases of fluorescence ratio signals with a kinetic model to quantify overall Ca(2+) removal. Results obtained with the two indicators were similar. Ca(2+) release was 2-3 orders of magnitude larger than the flux carried by the L-type Ca(2+) current. At maximal depolarization (+50 mV), release flux peaked at about 3 ms after the onset of the voltage pulse and then decayed in two distinct phases. The slower phase, most likely resulting from SR depletion, indicated a decrease in lumenal Ca(2+) content by about 80% within 100 ms. Unlike in frog fibres, the kinetics of the rapid phase of decay showed no dependence on the filling state of the SR and the results provide little evidence for a substantial increase of SR permeability on depletion. The approach described here promises insight into excitation-contraction coupling in future studies of genetically altered mice.
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Affiliation(s)
- D Ursu
- University of Ulm, Department of Applied Physiology, Albert-Einstein-Allee 11, D-89069 Ulm, Germany
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42
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Bruton JD, Dahlstedt AJ, Abbate F, Westerblad H. Mitochondrial function in intact skeletal muscle fibres of creatine kinase deficient mice. J Physiol 2004; 552:393-402. [PMID: 14561823 PMCID: PMC2343388 DOI: 10.1113/jphysiol.2003.050732] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Creatine kinase (CK) has a central role in skeletal muscle, acting as a fast energy buffer and shuttle between sites of energy production (mitochondria) and consumption (cross-bridges and ion pumps). Unexpectedly, isolated fast-twitch skeletal muscle cells of mice deficient in both cytosolic and mitochondrial CK (CK-/-) are highly fatigue resistant during stimulation protocols that stress aerobic metabolism. We have now studied different aspects of mitochondrial function in CK-/- skeletal muscle. Intact, single fibres of flexor digitorum brevis (FDB) muscles were fatigued by repeated tetanic stimulation (70 Hz, 350 ms duration, duty cycle 0.14). Under control conditions, CK-/- FDB fibres were more fatigue resistant than wild-type fibres. However, after mitochondrial inhibition with cyanide, force declined markedly faster in CK-/- fibres than in wild-type fibres. The rapid force decline in CK-/- fibres was not due to decreased myoplasmic [Ca2+] during tetani (measured with indo-1), which in these fibres remained virtually constant during fatigue in the presence of cyanide. Intact, single fibres of highly oxidative soleus muscles were fatigued by repeated tetani (50 Hz, 500 ms duration, duty cycle 0.5). All CK-/- soleus fibres tested (n = 9) produced > 40 % force at the end of the fatiguing stimulation period (500 tetani), whereas force fell to < 40 % before 500 tetani in two of three wild-type fibres. Mitochondrial [Ca2+] (measured with rhod-2 and confocal microscopy) increased during repeated tetanic stimulation in CK-/- but not in wild-type FDB fibres. In conclusion, mitochondria and energy shuttling operate effectively in CK-/- fibres and this is associated with an increase in mitochondrial [Ca2+].
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Affiliation(s)
- Joseph D Bruton
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77 Stockholm, Sweden
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43
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Allman BL, Rice CL. An age-related shift in the force-frequency relationship affects quadriceps fatigability in old adults. J Appl Physiol (1985) 2004; 96:1026-32. [PMID: 14594856 DOI: 10.1152/japplphysiol.00991.2003] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined the effect of an age-related leftward shift in the force-frequency relationship on the comparative quadriceps fatigability of nine young (27 ± 1 yr old) and nine old men (78 ± 1 yr old) during low-frequency electrical stimulation. Two different protocols of intermittent trains (6 pulses on, 650 ms off) of electrical stimulation at 25% maximum voluntary contraction were performed by both groups: 1) 180 trains at 14.3 Hz [constant frequency (CF) protocol], and 2) 180 trains at the frequency corresponding to 60% of each subject's force-frequency curve [normalized frequency (NF) protocol; young 14.9 ± 0.4 vs. old 12.7 ± 0.5 Hz; P < 0.05]. The quadriceps of the old men were weaker (∼31%) and relaxation was slower compared with the young men, as assessed by the maximal relaxation rate constant of the 50-Hz tetanus (young 12.1 ± 0.2 vs. old 9.2 ± 0.5 s-1; P < 0.05) and a leftward shift in the force-frequency relationship. The NF protocol revealed a decreased fatigability in the quadriceps with old age (percentage of 1st contraction force remaining at 180th: old 63.4 ± 1.5 vs. young 58.2 ± 1.7%; P < 0.05) that was masked during the CF protocol (old 60.7 ± 1.6 vs. young 58.6 ± 2.3%; P > 0.05). Irrespective of the protocol, the maximal relaxation rate was reduced to ∼73 and ∼57% of the prefatigue value in the young and old men, respectively. The age-related leftward shift in the force-frequency relationship of the quadriceps contributed to an underestimation of the fatigue resistance with old age during the CF protocol. However, when the stimulation frequency used in the NF protocol was adjusted to account for the age-related shift in the force-frequency relationship, the quadriceps muscles of the old men were less fatigable than those of the young men. Thus we suggest that whole muscle fatigability is better examined by electrical stimulation protocols that are adjusted for inter- and intragroup differences in the force-frequency relationship.
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Affiliation(s)
- Brian L Allman
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Canada
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44
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Koopman WJH, Renders M, Oosterhof A, van Kuppevelt TH, van Engelen BGM, Willems PHGM. Upregulation of Ca2+ removal in human skeletal muscle: a possible role for Ca2+-dependent priming of mitochondrial ATP synthesis. Am J Physiol Cell Physiol 2003; 285:C1263-9. [PMID: 12839829 DOI: 10.1152/ajpcell.00097.2003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In muscle, ATP is required for the powerstroke of the myosin head, the detachment of actin and myosin filaments, and the reuptake of Ca2+ into the sarcoplasmic reticulum. During contraction-relaxation, large amounts of ATP are consumed at the sites of action of the myosin-ATPase and sarcoplasmic reticulum Ca2+-ATPase. The present study addresses the consequences of a reduction in mitochondrial ATP production capacity on sarcoplasmic Ca2+ handling. To this end, myotubes were cultured from patient quadriceps with a biochemically defined decrease in the maximal rate of mitochondrial ATP production and were loaded with indo 1 for imaging of sarcoplasmic Ca2+ changes in real time by confocal microscopy. Myotubes were field-stimulated with 10-ms pulses of 16 V to evoke transient rises in sarcoplasmic Ca2+ concentration ([Ca2+]S). Three single pulses, two pulse trains (1 Hz), and one single pulse were applied in succession to mimic changing workloads. Control myotubes displayed [Ca2+]S transients with an amplitude that was independent of the strength of the stimulus. Intriguingly, the rate of sarcoplasmic Ca2+ removal (CRR) was significantly upregulated during the second and subsequent transients. In myotubes with a reduced mitochondrial ATP production capacity, the amplitude of the [Ca2+]S transients was markedly increased at higher stimulus intensities. Moreover, upregulation of the CRR was significantly decreased compared with control. Taken together, these results are in good agreement with a tight coupling between mitochondrial ATP production and sarcoplasmic Ca2+ handling. Moreover, they support the existence of a relatively long-lasting mitochondrial memory for sarcoplasmic [Ca2+] rises. This memory, which manifested itself as an increase in CRR upon recurrent stimulation, was impaired in patient myotubes with a reduced mitochondrial ATP production capacity.
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Affiliation(s)
- Werner J H Koopman
- 160 Biochemistry NCMLS, University Medical Center Nijmegen, PO Box 9101, NL-6500 HB Nijmegen, The Netherlands
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45
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Emre M, Karayaylali I, San M. Effects of trimetazidine and selenium on high-frequency fatigue in isolated rat diaphragm muscle. Adv Ther 2003; 20:261-9. [PMID: 14964346 DOI: 10.1007/bf02849855] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Trimetazidine (TMZ), which has been used in numerous experimental studies, is applied nowadays with the aim of reducing myocardial ischemia. The aim of this study was to determine the prefatigue and postfatigue contractile characteristics associated with the relationship between the force and frequency of contraction in muscle. The study was conducted using diaphragm muscle isolated from 40 male Wistar rats weighing 230 to 270 g. The rats were divided into 4 groups of 10 animals each: controls and TMZ-, selenium (Se)-, and TMZ+Se-treated groups. The rats in the control group were treated with 2 mL of physiologic serum (SF), those in the second group with Se 30 microg/kg in 2mL of SF, those in the third group with TMZ 5 mg/kg in 2 mL of SF, and those in the fourth group with a combination of TMZ 5 mg/kg + Se 30 microg/kg in 2 mL of SF. All rats were treated twice daily for 15 days by means of gastric lavage. The rats were then killed by cervical dislocation. The diaphragm muscle bands were removed and placed in an organ bath. After a 2-hour thermoregulatory period, muscles were fatigued with 5-ms pulses at a frequency of 40 Hz. Force-frequency relationships were studied after the application of 10, 50, and 100 Hz and the development of contraction curves. Contraction forces for the groups treated with TMZ, Se, and TMZ+Se (16.1 +/- 1.2, 13.2 +/- 1.3, and 14.9 +/- 1.0 g, respectively) were significantly lower than for the control group (17.0 +/- 1.4 g) during the prefatigue period (P<.001). Similarly, postfatigue contraction forces for the treated groups (15.7 +/- 1.3, 8.8 +/- 1.0, and 12.0 +/- 1.4 g, respectively) were significantly lower than for the control group (12.4 +/- 1.2 g, P<.001, P<.001, and P<.05, respectively). A significant decrease was noted in postfatigue contraction forces and contraction and relaxation rates in the Se- and TMZ+Se-treated groups compared with prefatigue values (P<.001), but the difference was not significant. Force-frequency relationships were evaluated at 10, 50, and 100 Hz. The tetanic contraction forces for the control, Se-, TMZ-, and TMZ+Se-treated groups at 100 Hz were 81.3 +/- 5.7, 91.6 +/- 6.8, 65.3 +/- 5.0, and 84.9 +/- 7.5 g, respectively. In the TMZ-treated group, a significant increase was observed in tetanic contraction forces at 100 Hz compared with controls (P<.001); no significant changes were seen in the force-frequency relationships at 10 and 50 Hz. The decrease in the contraction force in the postfatigue period was prevented to a larger extent in the TMZ-treated group than in the TMZ+Se- and Se-treated groups.
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Affiliation(s)
- Mustafa Emre
- Cukurova University Medical School, Department of Biophysics, Balcali-Adana, Turkey
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46
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Johansson C, Lunde PK, Gothe S, Lannergren J, Westerblad H. Isometric force and endurance in skeletal muscle of mice devoid of all known thyroid hormone receptors. J Physiol 2003; 547:789-96. [PMID: 12562961 PMCID: PMC2342733 DOI: 10.1113/jphysiol.2002.032086] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The importance of thyroid hormone receptors for isometric force, endurance and content of specific muscle enzymes was studied in isolated slow-twitch soleus and fast-twitch extensor digitorum longus (EDL) muscles in mice deficient in all known subtypes of thyroid hormone receptors (i.e. TR alpha1, beta1, beta2 and beta3). The weights of soleus and EDL muscles were lower in TR-deficient (TRalpha1-/-beta-/-) mice than in wild-type controls. The force per cross-sectional area was not significantly different between TRalpha1-/-beta-/- and wild-type muscles. Soleus muscles of TRalpha1-/-beta-/- mice showed increased contraction and relaxation times and the force-frequency relationship was shifted to the left. Soleus muscles of TRalpha1-/-beta-/- mice were more fatigue resistant than wild-type controls. Protein analysis of TRalpha1-/-beta-/- soleus muscles showed a marked increase in expression of the slow isoform of the sarcoplasmic reticulum Ca2+ pump (SERCa2), whilst expression of the fast type (SERCa1) was decreased. There was also a major decrease in the alpha2-subunit of the Na+-K+ pump in TRalpha1-/-beta-/- soleus muscles. EDL muscles from TRalpha1-/-beta-/- and wild-type mice showed no significant difference in contraction and relaxation times, fatigue resistance and protein expression. In conclusion, the present data show changes in contractile characteristics of skeletal muscles of TRalpha1-/-beta-/- mice similar to those seen in hypothyroidism. We have previously shown that muscles of mice deficient in TRalpha1 or TRbeta display modest changes in muscle function. Thus, in skeletal muscle there seems to be functional overlap between TRalpha1 and TRbeta, so that the lack of one of the receptors to some extent can be compensated for by the presence of the other.
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MESH Headings
- Animals
- Blotting, Western
- Isometric Contraction/physiology
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Mice, Mutant Strains
- Muscle Fatigue/physiology
- Muscle Fibers, Fast-Twitch/chemistry
- Muscle Fibers, Fast-Twitch/physiology
- Muscle Fibers, Slow-Twitch/chemistry
- Muscle Fibers, Slow-Twitch/physiology
- Muscle Relaxation/physiology
- Muscle, Skeletal/cytology
- Muscle, Skeletal/physiology
- Physical Endurance/physiology
- Thyroid Hormone Receptors alpha/analysis
- Thyroid Hormone Receptors alpha/genetics
- Thyroid Hormone Receptors beta/analysis
- Thyroid Hormone Receptors beta/genetics
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Affiliation(s)
- Catarina Johansson
- Department of Physiology and Pharmacology, Karolinska Institute, S-171 77 Stockholm, Sweden
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Garland SJ, Walton D, Ivanova TD. Effect of force level and training status on contractile properties following fatigue. CANADIAN JOURNAL OF APPLIED PHYSIOLOGY = REVUE CANADIENNE DE PHYSIOLOGIE APPLIQUEE 2003; 28:93-101. [PMID: 12671198 DOI: 10.1139/h03-008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study examined the effects of fatigue on the contractile properties of the twitch contraction evoked by the H-reflex and the maximal M-wave. Untrained subjects demonstrated more pronounced slowing of half relaxation time (HRT) in the H-reflex twitch than in the M-wave twitch and also more slowing of HRT in high force vs. low force contractions. Endurance-trained subjects, however, demonstrated a shortening of the H-reflex twitch. The twitch contractile properties following fatigue are dependent on force level and training status.
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Affiliation(s)
- S Jayne Garland
- School of Physical Therapy, Elborn College, the University of Western Ontario, London, ON N6G 1H1
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Lännergren J, Westerblad H, Bruton JD. Changes in mitochondrial Ca2+ detected with Rhod-2 in single frog and mouse skeletal muscle fibres during and after repeated tetanic contractions. J Muscle Res Cell Motil 2002; 22:265-75. [PMID: 11763199 DOI: 10.1023/a:1012227009544] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The present study investigated mitochondrial Ca2+ uptake and release in intact living skeletal muscle fibres subjected to bouts of repetitive activity. Confocal microscopy was used in conjunction with the Ca2+-sensitive dye Rhod-2 to monitor changes in mitochondrial Ca2+ in single Xenopus or mouse muscle fibres. A marked increase in the mitochondrial Ca2+ occurred in Xenopus fibres after 10 tetani applied at 4 s intervals. The mitochondrial Ca2+ continued to increase with increasing number of tetani. After the end of tetanic stimulation, mitochondrial Ca2+ declined to 50% of the maximal increase within 10 min and thereafter took up to 60 min to return to its original value. Depolarization of the mitochondria with FCCP greatly attenuated the rise in the mitochondrial Ca2+ evoked by repetitive tetanic stimulation. In addition, FCCP slowed the rate of decay of the tetanic Ca2+ transient which in turn led to an elevation of resting cytosolic Ca2+. Accumulation of Ca2+ in the mitochondria was accompanied by a modest mitochondrial depolarization. In contrast to the situation in Xenopus fibres, mitochondria in mouse toe muscle fibres did not show any change in the mitochondrial Ca2+ during repetitive stimulation and FCCP had no effect on the rate of decay of the tetanic Ca2+ transient. It is concluded that in Xenopus fibres, mitochondria play a role in the regulation of cytosolic Ca2+ and contribute to the relaxation of tetanic Ca2+ transients. In contrast to their important role in Xenopus fibres, mitochondria in mouse fast-twitch skeletal fibres play little role in Ca2+ homeostasis.
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Affiliation(s)
- J Lännergren
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
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49
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Ding J, Wexler AS, Binder-Macleod SA. A predictive fatigue model--I: Predicting the effect of stimulation frequency and pattern on fatigue. IEEE Trans Neural Syst Rehabil Eng 2002; 10:48-58. [PMID: 12173739 DOI: 10.1109/tnsre.2002.1021586] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Previously we developed a mathematical force- and fatigue-model system that could predict fatigue produced by a wide range of frequencies and pulse patterns. However, the models tended to overestimate the forces produced by higher frequency trains. This paper presents modifications to our previously developed force- and fatigue-model system to improve the accuracy in predicting forces during repetitive activation of human skeletal muscle. By comparing the predictions produced by the modified force and fatigue models to those by our previous models, the modification appears to be successful. The current force- and fatigue-model system accounts for about 93% variance in experimental data produced by fatigue protocols consisting of trains with a wide range of frequencies and pulse patterns. In addition, the present models successfully predict the effect of stimulation frequency and pulse pattern on muscle fatigue. The success of our current force- and fatigue-model system suggests its potential use in helping to identify the optimal activation pattern to use during the clinical application of functional electrical stimulation.
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Affiliation(s)
- Jun Ding
- Interdisciplinary Graduate Program in Biomechanics and Movement Science, University of Delaware, Newark 19716, USA
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50
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Verburg E, Thorud HM, Eriksen M, Vøllestad NK, Sejersted OM. Muscle contractile properties during intermittent nontetanic stimulation in rat skeletal muscle. Am J Physiol Regul Integr Comp Physiol 2001; 281:R1952-65. [PMID: 11705782 DOI: 10.1152/ajpregu.2001.281.6.r1952] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To examine changes in contractile properties and mechanisms of fatigue during submaximal nontetanic skeletal muscle activity, in situ perfused soleus (60-min protocol) and extensor digitorum longus (EDL; 10-min protocol) muscles of the rat were electrically stimulated intermittently at low frequency. The partly fused trains of contractions showed a two-phase change in appearance. During the first phase, relaxation slowed, one-half relaxation time increased, and maximal relaxation first derivative of force (dF/dt) decreased. Developed force during the trains was reduced and was closely related to the rate of relaxation in this first phase. During the second phase, relaxation became faster again, one-half relaxation time decreased, and force returned to resting levels between contractions in a train. In contrast, developed force remained reduced, so that peak force of the contractions was 51% (soleus) and 30% (EDL) of control. In the soleus muscle, the changes in contractile properties were not related to ATP, creatine phosphate, or lactate content. The changes in contractile properties fit best with a mechanism of fatigue involving changes in Ca(2+) handling by the sarcoplasmic reticulum.
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Affiliation(s)
- E Verburg
- Institute for Experimental Medical Research, University of Oslo, Ullevaal Hospital, N-0407 Oslo, Norway
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