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Paish AD, Zero AM, McNeil CJ, Rice CL. Increased corticospinal inhibition following brief maximal and submaximal contractions in humans. J Appl Physiol (1985) 2023; 135:805-811. [PMID: 37616335 DOI: 10.1152/japplphysiol.00206.2023] [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: 03/31/2023] [Revised: 07/31/2023] [Accepted: 08/22/2023] [Indexed: 08/26/2023] Open
Abstract
A potentiating conditioning contraction (CC) has been shown to increase silent period duration, an index of corticospinal inhibition; however, it is unknown if the CC must induce potentiation for corticospinal inhibition to increase. Ten healthy, young adults (four females) completed this study to assess potentiation and silent period (SP) duration before and after four types of CCs: voluntary and electrically evoked maximal CCs to optimize potentiation, and voluntary and electrically evoked submaximal CCs (∼40% of maximal voluntary force) that induced minimal potentiation. Stimulation was applied to the ulnar nerve to evoke twitches for the assessment of potentiation and to evoke tetanic CCs of the first dorsal interosseous muscle. The SP was elicited by applying transcranial magnetic stimulation to the motor cortex during brief contractions at 25% of maximal voluntary force. Changes to twitch force and SP duration were not different for voluntary and tetanic contractions, so data were pooled. Twitch force increased by 81.2 ± 35.7% (P < 0.001) and 3.2 ± 6.5% (P = 0.039) following maximal and submaximal CCs, respectively. The SP was prolonged following maximal (12.6 ± 6.3%; P < 0.001) and submaximal (4.8 ± 4.9%; P < 0.001) CCs. Correlations between post-CC twitch force and SP duration were not significant for maximal or submaximal conditions (r = -0.068; r = 0.067; P ≥ 0.780, respectively). Duration of the SP increased not only following maximal-intensity CCs but also after submaximal-intensity CCs that induced virtually no potentiation (∼3%). Thus, we suggest that corticospinal inhibition is not directly related to mechanisms of muscle potentiation per se, but, rather, the level of muscle contraction likely mediates feedback from large diameter afferents that affect the SP.NEW & NOTEWORTHY The transcranial magnetic stimulation-induced silent period reflects a transient state of corticospinal inhibition that is influenced by recent history of muscle activation, which may include an effect of potentiation. We demonstrate that silent period duration increases following both voluntary and electrically evoked maximal and submaximal conditioning contractions, even though the latter intensity produced virtually no muscle potentiation. Feedback from group Ia and Ib muscle afferents is proposed as the cause of the increased corticospinal inhibition.
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Affiliation(s)
- Alexander D Paish
- Faculty of Health Sciences, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Alexander M Zero
- Faculty of Health Sciences, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Chris J McNeil
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Charles L Rice
- Faculty of Health Sciences, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
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Hahn D, Han SW, Joumaa V. The history-dependent features of muscle force production: A challenge to the cross-bridge theory and their functional implications. J Biomech 2023; 152:111579. [PMID: 37054597 DOI: 10.1016/j.jbiomech.2023.111579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2023] [Accepted: 04/03/2023] [Indexed: 04/15/2023]
Abstract
The cross-bridge theory predicts that muscle force is determined by muscle length and the velocity of active muscle length changes. However, before the formulation of the cross-bridge theory, it had been observed that the isometric force at a given muscle length is enhanced or depressed depending on active muscle length changes before that given length is reached. These enhanced and depressed force states are termed residual force enhancement (rFE) and residual force depression (rFD), respectively, and together they are known as the history-dependent features of muscle force production. In this review, we introduce early attempts in explaining rFE and rFD before we discuss more recent research from the past 25 years which has contributed to a better understanding of the mechanisms underpinning rFE and rFD. Specifically, we discuss the increasing number of findings on rFE and rFD which challenge the cross-bridge theory and propose that the elastic element titin plays a role in explaining muscle history-dependence. Accordingly, new three-filament models of force production including titin seem to provide better insight into the mechanism of muscle contraction. Complementary to the mechanisms behind muscle history-dependence, we also show various implications for muscle history-dependence on in-vivo human muscle function such as during stretch-shortening cycles. We conclude that titin function needs to be better understood if a new three-filament muscle model which includes titin, is to be established. From an applied perspective, it remains to be elucidated how muscle history-dependence affects locomotion and motor control, and whether history-dependent features can be changed by training.
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Affiliation(s)
- Daniel Hahn
- Human Movement Science, Faculty of Sport Science, Ruhr University, Bochum, Germany; School of Human Movement and Nutrition Sciences, University of Queensland, Australia
| | - Seong-Won Han
- Institute of Physiology II, Faculty of Medicine, University of Münster, Germany.
| | - Venus Joumaa
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Alberta, Canada
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Contento VS, Power GA. Eccentric exercise-induced muscle weakness amplifies the history dependence of force. Eur J Appl Physiol 2023; 123:749-767. [PMID: 36447012 DOI: 10.1007/s00421-022-05105-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 11/16/2022] [Indexed: 12/05/2022]
Abstract
INTRODUCTION Following active lengthening or shortening contractions, isometric steady-state torque is increased (residual force enhancement; rFE) or decreased (residual force depression; rFD), respectively, compared to fixed-end isometric contractions at the same muscle length and level of activation. Though the mechanisms underlying this history dependence of force have been investigated extensively, little is known about the influence of exercise-induced muscle weakness on rFE and rFD. PURPOSE Assess rFE and rFD in the dorsiflexors at 20%, 60%, and 100% maximal voluntary torque (MVC) and activation matching, and electrically stimulated at 20% MVC, prior to, 1 h following, and 24 h following 150 maximal eccentric dorsiflexion contractions. METHODS Twenty-six participants (13 male, 24.7 ± 2.0y; 13 female, 22.5 ± 3.6y) were seated in a dynamometer with their right hip and knee angle set to 110° and 140°, respectively, with an ankle excursion set between 0° and 40° plantar flexion (PF). MVC torque, peak twitch torque, and prolonged low frequency force depression were used to assess eccentric exercise-induced neuromuscular impairments. History-dependent contractions consisted of a 1 s isometric (40°PF or 0°PF) phase, a 1 s shortening or lengthening phase (40°/s), and an 8 s isometric (0°PF or 40°PF) phase. RESULTS Following eccentric exercise; MVC torque was decreased, prolonged low frequency force depression was present, and both rFE and rFD increased for all maximal and submaximal conditions. CONCLUSIONS The history dependence of force during voluntary torque and activation matching, and electrically stimulated contractions is amplified following eccentric exercise. It appears that a weakened neuromuscular system amplifies the magnitude of the history-dependence of force.
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Affiliation(s)
- Vincenzo S Contento
- Department of Human Health and Nutritional Sciences, College of Biological Science, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Geoffrey A Power
- Department of Human Health and Nutritional Sciences, College of Biological Science, University of Guelph, Guelph, ON, N1G 2W1, Canada.
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Frischholz J, Raiteri BJ, Cresswell AG, Hahn D. Corticospinal excitability remains unchanged in the presence of residual force enhancement and does not contribute to increased torque production. PeerJ 2022; 10:e12729. [PMID: 35036100 PMCID: PMC8743010 DOI: 10.7717/peerj.12729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 12/10/2021] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Following stretch of an active muscle, muscle force is enhanced, which is known as residual force enhancement (rFE). As earlier studies found apparent corticospinal excitability modulations in the presence of rFE, this study aimed to test whether corticospinal excitability modulations contribute to rFE. METHODS Fourteen participants performed submaximal plantar flexion stretch-hold and fixed-end contractions at 30% of their maximal voluntary soleus muscle activity in a dynamometer. During the steady state of the contractions, participants either received subthreshold or suprathreshold transcranial magnetic stimulation (TMS) of their motor cortex, while triceps surae muscle responses to stimulation were obtained via electromyography (EMG), and net ankle joint torque was recorded. B-mode ultrasound imaging was used to confirm muscle fascicle stretch during stretch-hold contractions in a subset of participants. RESULTS Following stretch of the plantar flexors, an average rFE of 7% and 11% was observed for contractions with subthreshold and suprathreshold TMS, respectively. 41-46 ms following subthreshold TMS, triceps surae muscle activity was suppressed by 19-25%, but suppression was not significantly different between stretch-hold and fixed-end contractions. Similarly, the reduction in plantar flexion torque following subthreshold TMS was not significantly different between contraction conditions. Motor evoked potentials, silent periods and superimposed twitches following suprathreshold TMS were also not significantly different between contraction conditions. DISCUSSION As TMS of the motor cortex did not result in any differences between stretch-hold and fixed-end contractions, we conclude that rFE is not linked to changes in corticospinal excitability.
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Affiliation(s)
- Jasmin Frischholz
- Human Movement Science, Faculty of Sport Science, Ruhr University Bochum, Bochum, Germany
| | - Brent J. Raiteri
- Human Movement Science, Faculty of Sport Science, Ruhr University Bochum, Bochum, Germany
| | - Andrew G. Cresswell
- School of Human Movement and Nutrition Sciences, University of Queensland, Brisbane, Australia
| | - Daniel Hahn
- Human Movement Science, Faculty of Sport Science, Ruhr University Bochum, Bochum, Germany,School of Human Movement and Nutrition Sciences, University of Queensland, Brisbane, Australia
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de Campos D, Orssatto LBR, Trajano GS, Herzog W, Fontana HDB. Residual force enhancement in human skeletal muscles: A systematic review and meta-analysis. JOURNAL OF SPORT AND HEALTH SCIENCE 2022; 11:94-103. [PMID: 34062271 PMCID: PMC8847921 DOI: 10.1016/j.jshs.2021.05.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 02/21/2021] [Accepted: 03/15/2021] [Indexed: 05/05/2023]
Abstract
OBJECTIVE We reviewed and appraised the existing evidence of in vivo manifestations of residual force enhancement in human skeletal muscles and assessed, through a meta-analysis, the effect of an immediate history of eccentric contraction on the subsequent torque capacity of voluntary and electrically evoked muscle contractions. METHODS Our search was conducted from database inception to May 2020. Descriptive information was extracted from, and quality was assessed for, 45 studies. Meta-analyses and metaregressions were used to analyze residual torque enhancement and its dependence on the angular amplitude of the preceding eccentric contraction. RESULTS Procedures varied across studies with regards to muscle group tested, angular stretch amplitude, randomization of contractions, time window analyzed, and verbal command. Torque capacity in isometric (constant muscle tendon unit length and joint angle) contractions preceded by an eccentric contraction was typically greater compared to purely isometric contractions, and this effect was greater for electrically evoked muscle contractions than voluntary contractions. Residual torque enhancement differed across muscle groups for the voluntary contractions, with a significant enhancement in torque observed for the adductor pollicis, ankle dorsiflexors, ankle plantar flexors, and knee extensors, but not for the elbow and knee flexors. Meta-regressions revealed that the angular amplitude of the eccentric contraction (normalized to the respective joint's full range of motion) was not associated with the residual torque enhancement observed. CONCLUSION There is evidence of residual torque enhancement for most, but not all, muscle groups, and residual torque enhancement is greater for electrically evoked than for voluntary contractions. Contrary to our hypothesis, and contrary to generally accepted findings on isolated muscle preparations, residual torque enhancement in voluntary and electrically evoked contractions does not seem to depend on the angular amplitude of the preceding eccentric contraction.
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Affiliation(s)
- Daiani de Campos
- Biomechanics Laboratory, Federal University of Santa Catarina, Florianopolis 88040-001, Brazil
| | - Lucas B R Orssatto
- Faculty of Health, School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane QLD 4030, Australia
| | - Gabriel S Trajano
- Faculty of Health, School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane QLD 4030, Australia
| | - Walter Herzog
- Biomechanics Laboratory, Federal University of Santa Catarina, Florianopolis 88040-001, Brazil; Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, AB T2N 1N4, Canada
| | - Heiliane de Brito Fontana
- Biomechanics Laboratory, Federal University of Santa Catarina, Florianopolis 88040-001, Brazil; School of Biological Sciences, Federal University of Santa Catarina, Florianopolis 88040-900, Brazil.
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Maximal and submaximal isometric torque is elevated immediately following highly controlled active stretches of the hamstrings. J Electromyogr Kinesiol 2021; 56:102500. [DOI: 10.1016/j.jelekin.2020.102500] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 10/29/2020] [Accepted: 11/09/2020] [Indexed: 01/22/2023] Open
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Chapman ND, Whitting JW, Broadbent S, Crowley-McHattan ZJ, Meir R. Residual Force Enhancement Is Present in Consecutive Post-Stretch Isometric Contractions of the Hamstrings during a Training Simulation. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:1154. [PMID: 33525530 PMCID: PMC7908171 DOI: 10.3390/ijerph18031154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 01/21/2021] [Accepted: 01/25/2021] [Indexed: 11/17/2022]
Abstract
Residual force enhancement (rFE) is observed when isometric force following an active stretch is elevated compared to an isometric contraction at corresponding muscle lengths. Acute rFE has been confirmed in vivo in upper and lower limb muscles. However, it is uncertain whether rFE persists using multiple, consecutive contractions as per a training simulation. Using the knee flexors, 10 recreationally active participants (seven males, three females; age 31.00 years ± 8.43 years) performed baseline isometric contractions at 150° knee flexion (180° representing terminal knee extension) of 50% maximal voluntary activation of semitendinosus. Participants performed post-stretch isometric (PS-ISO) contractions (three sets of 10 repetitions) starting at 90° knee extension with a joint rotation of 60° at 60°·s-1 at 50% maximal voluntary activation of semitendinosus. Baseline isometric torque and muscle activation were compared to PS-ISO torque and muscle activation across all 30 repetitions. Significant rFE was noted in all repetitions (37.8-77.74%), with no difference in torque between repetitions or sets. There was no difference in activation of semitendinosus or biceps femoris long-head between baseline and PS-ISO contractions in all repetitions (ST; baseline ISO = 0.095-1.000 ± 0.036-0.039 Mv, PS-ISO = 0.094-0.098 ± 0.033-0.038 and BFlh; baseline ISO = 0.068-0.075 ± 0.031-0.038 Mv). This is the first investigation to observe rFE during multiple, consecutive submaximal PS-ISO contractions. PS-ISO contractions have the potential to be used as a training stimulus.
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Affiliation(s)
- Neil D. Chapman
- School of Health and Human Sciences, Southern Cross University, Lismore, NSW 2480, Australia; (J.W.W.); (S.B.); (Z.J.C.-M.); (R.M.)
- Faculty of Health Sciences and Medicine, Bond University, Robina, QLD 4229, Australia
| | - John W. Whitting
- School of Health and Human Sciences, Southern Cross University, Lismore, NSW 2480, Australia; (J.W.W.); (S.B.); (Z.J.C.-M.); (R.M.)
| | - Suzanne Broadbent
- School of Health and Human Sciences, Southern Cross University, Lismore, NSW 2480, Australia; (J.W.W.); (S.B.); (Z.J.C.-M.); (R.M.)
- School of Health and Behavioural Sciences, University of the Sunshine Coast, Sippy Downs, QLD 4556, Australia
| | - Zachary J. Crowley-McHattan
- School of Health and Human Sciences, Southern Cross University, Lismore, NSW 2480, Australia; (J.W.W.); (S.B.); (Z.J.C.-M.); (R.M.)
| | - Rudi Meir
- School of Health and Human Sciences, Southern Cross University, Lismore, NSW 2480, Australia; (J.W.W.); (S.B.); (Z.J.C.-M.); (R.M.)
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Power GA, Hinks A, Mashouri P, Contento VS, Chen J. The long and short of residual force enhancement non-responders. Eur J Appl Physiol 2020; 120:2565-2567. [DOI: 10.1007/s00421-020-04511-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Jakobi JM, Kuzyk SL, McNeil CJ, Dalton BH, Power GA. Motor unit contributions to activation reduction and torque steadiness following active lengthening: a study of residual torque enhancement. J Neurophysiol 2020; 123:2209-2216. [PMID: 32347154 DOI: 10.1152/jn.00394.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Following active lengthening, steady-state isometric (ISO) torque is greater than a purely ISO contraction at the same muscle length, this is referred to as residual torque enhancement (rTE). A phenomenon of rTE is activation reduction, characterized by reduced electromyography (EMG) amplitude for a given torque output. We hypothesized that lower motor unit discharge rates would contribute to activation reduction and lessening torque steadiness. Ten young male subjects performed ISO dorsiflexion contractions at 10 and 20% of maximal voluntary contraction (MVC) torque. During rTE trials, the muscle was activated at 10° of plantar flexion, then the ankle was rotated to the ISO position at 40°. Fine wire electrodes recorded motor unit (MU)-discharge rates and variability from the tibialis anterior. Surface EMG quantified activation reduction, and steadiness was determined as the coefficient of variation of torque. The activation reduction was 44 and 24% at 10 and 20% MVC, respectively (P < 0.05). Fewer MUs were recorded in the rTE than ISO condition at 10% (~47%) and 20% (~36%) MVC (P < 0.05). Discharge rates were 19 and 26% lower in the rTE compared with the ISO condition for 10 and 20% MVC, respectively (P < 0.05), with no difference in variability between conditions (P > 0.05). Steadiness was ~22 and 18% lower for the rTE than ISO condition at 10 and 20% MVC (P < 0.05). Our findings indicate that activation reduction may be attributed to lower MU discharge rate and fewer detectable MUs and that this theoretically contributes to a reduction in steadiness in the rTE condition.NEW & NOTEWORTHY Our findings indicate that lower electromyographic activity during the torque enhanced condition following active lengthening compared with a purely isometric contraction arises from fewer active motor units and a lower discharge rate of those that are active. We used an acute condition of increased torque capacity to induce a decrease in net output of the motor neuron pool during a submaximal task to demonstrate, in humans, the impact of motor unit activity on torque steadiness.
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Affiliation(s)
- Jennifer M Jakobi
- School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia, Okanagan, British Columbia, Canada
| | - Samantha L Kuzyk
- School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia, Okanagan, British Columbia, Canada
| | - Chris J McNeil
- School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia, Okanagan, British Columbia, Canada
| | - Brian H Dalton
- School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia, Okanagan, British Columbia, Canada
| | - Geoffrey A Power
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, Ontario, Canada
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Contento VS, Dalton BH, Power GA. The Inhibitory Tendon-Evoked Reflex Is Increased in the Torque-Enhanced State Following Active Lengthening Compared to a Purely Isometric Contraction. Brain Sci 2019; 10:brainsci10010013. [PMID: 31878094 PMCID: PMC7016668 DOI: 10.3390/brainsci10010013] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 12/16/2019] [Accepted: 12/18/2019] [Indexed: 11/16/2022] Open
Abstract
Residual torque enhancement (rTE) is a history-dependent property of muscle, which results in an increase in steady-state isometric torque production following an active lengthening contraction as compared to a purely isometric (ISO) contraction at the same muscle length and level of activation. Once thought to be only an intrinsic property of muscle, recent evidence during voluntary contractions indicates a neuromechanical coupling between motor neuron excitability and the contractile state of the muscle. However, the mechanism by which this occurs has yet to be elucidated. The purpose of this study was to investigate inhibition arising from tendon-mediated feedback (e.g., Golgi tendon organ; GTO) through tendon electrical stimulation (TStim) in the ISO and rTE states during activation-matching and torque-matching tasks. Fourteen male participants (22 ± 2 years) performed 10 activation-matching contractions at 40% of their maximum tibialis anterior electromyography amplitude (5 ISO/5 rTE) and 10 torque-matching contractions at 40% of their maximum dorsiflexion torque (5 ISO/5 rTE). During both tasks, 10 TStim were delivered during the isometric steady state of all contractions, and the resulting tendon-evoked inhibitory reflexes were averaged and analyzed. Reflex amplitude increased by ~23% in the rTE state compared to the ISO state for the activation-matching task, and no differences were detected for the torque-matching task. The current data indicate an important relationship between afferent feedback in the torque-enhanced state and voluntary control of submaximal contractions. The history-dependent properties of muscle is likely to alter motor neuron excitability through modifications in tension- or torque-mediated afferent feedback arising from the tendon.
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Affiliation(s)
- Vincenzo S. Contento
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada;
| | - Brian H. Dalton
- School of Health and Exercise Science, University of British Columbia, Kelowna, BC V1V 1V7, Canada;
| | - Geoffrey A. Power
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada;
- Correspondence:
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Chen J, Power GA. Modifiability of the history dependence of force through chronic eccentric and concentric biased resistance training. J Appl Physiol (1985) 2018; 126:647-657. [PMID: 30571280 DOI: 10.1152/japplphysiol.00928.2018] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The increase and decrease in steady-state isometric force following active muscle lengthening and shortening are referred to as residual force enhancement (RFE) and force depression (FD), respectively. The RFE and FD states are associated with decreased (activation reduction; AR) and increased (activation increase; AI) neuromuscular activity, respectively. Although the mechanisms have been discussed over the last 60 years, no studies have systematically investigated the modifiability of RFE and FD with training. The purpose of the present study was to determine whether RFE and FD could be modulated through eccentric and concentric biased resistance training. Fifteen healthy young adult men (age: 24 ± 2 yr, weight: 77 ± 8 kg, height: 178 ± 5 cm) underwent 4 wk of isokinetic dorsiflexion training, in which one leg was trained eccentrically (-25°/s) and the other concentrically (+25°/s) over a 50° ankle excursion. Maximal and submaximal (40% maximum voluntary contraction) steady-state isometric torque and EMG values following active lengthening and shortening were compared to purely isometric values at the same joint angles and torque levels. Residual torque enhancement (rTE) decreased by ~36% after eccentric training ( P < 0.05) and increased by ~89% after concentric training ( P < 0.05), whereas residual torque depression (rTD), AR, AI, and optimal angles for torque production were not significantly altered by resistance training ( P ≥ 0.05). It appears that rTE, but not rTD, for the human ankle dorsiflexors is differentially modifiable through contraction type-dependent resistance training. NEW & NOTEWORTHY The history dependence of force production is a property of muscle unexplained by current cross bridge and sliding filament theories. Whether a muscle is actively lengthened (residual force enhancement; RFE) or shortened (force depression) to a given length, the isometric force should be equal to a purely isometric contraction-but it is not! In this study we show that eccentric training decreased RFE, whereas concentric training increased RFE and converted all nonresponders (i.e., not exhibiting RFE) into responders.
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Affiliation(s)
- Jackey Chen
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph , Guelph, Ontario , Canada
| | - Geoffrey A Power
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph , Guelph, Ontario , Canada
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Sypkes CT, Contento VS, Bent LR, McNeil CJ, Power GA. Central contributions to torque depression: an antagonist perspective. Exp Brain Res 2018; 237:443-452. [PMID: 30456694 DOI: 10.1007/s00221-018-5435-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 11/13/2018] [Indexed: 11/30/2022]
Abstract
Torque depression (TD) is the reduction in steady-state isometric torque following active muscle shortening when compared to an isometric reference contraction at the same muscle length and activation level. Central nervous system excitability differs in the TD state. While torque production about a joint is influenced by both agonist and antagonist muscle activation, investigations of corticospinal excitability have focused on agonist muscle groups. Hence, it is unknown how the TD state affects spinal and supraspinal excitability of an antagonist muscle. Eight participants (~ 24y, three female) performed 14 submaximal dorsiflexion contractions at the intensity needed to maintain a level of integrated electromyographic activity in the soleus equivalent to 15% of that recorded during a maximum plantar flexion contraction. The seven contractions of the TD protocol included a 2 s isometric phase at an ankle angle of 140°, a 1 s shortening phase at 40°/s, and a 7 s isometric phase at an angle of 100°. The seven isometric reference contractions were performed at an ankle angle of 100° for 10 s. Motor evoked potentials (MEPs), cervicomedullary motor evoked potentials (CMEPs), and maximal M-waves (Mmax) were recorded from the soleus in both conditions. In the TD compared to isometric reference state, a 13% reduction in dorsiflexor torque was accompanied by 10% lower spinal excitability (normalized CMEP amplitude; CMEP/Mmax), and 17% greater supraspinal excitability (normalized MEP amplitude; MEP/CMEP) for the soleus muscle. These findings demonstrate a neuromechanical coupling following active muscle shortening and indicate that the underlying mechanisms of TD influence antagonist activation during voluntary force production.
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Affiliation(s)
- Caleb T Sypkes
- Neuromechanical Performance Research Laboratory, Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON, Canada
| | - Vincenzo S Contento
- Neuromechanical Performance Research Laboratory, Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON, Canada
| | - Leah R Bent
- Neuromechanical Performance Research Laboratory, Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON, Canada
| | - Chris J McNeil
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - Geoffrey A Power
- Neuromechanical Performance Research Laboratory, Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON, Canada.
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