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Uçar N, Öner H, Kuş MA, Karaca H, Fırat T. The effect of neuromuscular electrical stimulation applied at different muscle lengths on muscle architecture and sarcomere morphology in rats. Anat Rec (Hoboken) 2024; 307:356-371. [PMID: 37194371 DOI: 10.1002/ar.25240] [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: 12/30/2022] [Revised: 04/04/2023] [Accepted: 04/26/2023] [Indexed: 05/18/2023]
Abstract
Neuromuscular electrical stimulation (NMES) is often used to increase muscle strength and functionality. Muscle architecture is important for the skeletal muscle functionality. The aim of this study was to investigate the effects of NMES applied at different muscle lengths on skeletal muscle architecture. Twenty-four rats were randomly assigned to four groups (two NMES groups and two control groups). NMES was applied on the extensor digitorum longus muscle at long muscle length, which is the longest and stretched position of the muscle at 170° plantar flexion, and at medium muscle length, which is the length of the muscle at 90° plantar flexion. A control group was created for each NMES group. NMES was applied for 8 weeks, 10 min/day, 3 days/week. After 8 weeks, muscle samples were removed at the NMES intervention lengths and examined macroscopically, and microscopically using a transmission electron microscope and streo-microscope. Muscle damage, and architectural properties of the muscle including pennation angle, fibre length, muscle length, muscle mass, physiological cross-sectional area, fibre length/muscle length, sarcomere length, sarcomere number were then evaluated. There was an increase in fibre length and sarcomere number, and a decrease in pennation angle at both lengths. In the long muscle length group, muscle length was increased, but widespread muscle damage was observed. These results suggest that the intervention of NMES at long muscle length can increase the muscle length but also causes muscle damage. In addition, the greater longitudinal increase in muscle length may be a result of the continuous degeneration-regeneration cycle.
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Affiliation(s)
- Nehir Uçar
- Department of Therapy and Rehabilitation, Vocational School of Health Sciences, University of Burdur Mehmet Akif Ersoy, Burdur, Turkey
| | - Hakan Öner
- Department of Histology and Embryology, Faculty of Veterinary Medicine, University of Burdur Mehmet Akif Ersoy, Burdur, Turkey
| | - Murat Abdulgani Kuş
- Department of Emergency Aid and Disaster Management, University of Burdur Mehmet Akif Ersoy, Burdur, Turkey
| | - Harun Karaca
- Department of Histology and Embryology, Faculty of Veterinary Medicine, University of Burdur Mehmet Akif Ersoy, Burdur, Turkey
| | - Tüzün Fırat
- Faculty of Physical Therapy and Rehabilitation, Hacettepe University, Ankara, Turkey
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2
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Rice PE, Nimphius S. When Task Constraints Delimit Movement Strategy: Implications for Isolated Joint Training in Dancers. Front Sports Act Living 2020; 2:49. [PMID: 33345041 PMCID: PMC7739566 DOI: 10.3389/fspor.2020.00049] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 04/07/2020] [Indexed: 12/18/2022] Open
Abstract
Athletic performance is determined by numerous variables that cannot always be controlled or modified. Due to aesthetic requirements during sports such as dance, body alignment constrains possible movement solutions. Increased power transference around the ankle-joint, coupled with lower hip-joint power, has become a preferential strategy in dancers during leaps and may be considered a dance-specific stretch-shortening cycle (SSC) demand. Newell's theoretical model of interacting constraints includes organismic (or individual), environmental, and task constraints describing the different endogenous and exogenous constraints individuals must overcome for movement and athletic performance. The unique task constraints imposed during dance will be used as a model to justify an isolated joint, single-targeted block progression training to improve physical capacity within the context of motor behavior to enhance dance-specific SSC performance. The suggested ankle-specific block progression consists of isometrics, dynamic constant external resistance, accentuated eccentrics, and plyometrics. Such programming tactics intend to collectively induce tendon remodeling, muscle hypertrophy, greater maximal strength, improved rate of force development, increased motor unit firing rates, and enhanced dynamic movement performance. The current perspective provides a dualistic approach and justification (physiological and motor behavioral) for specific strength and conditioning programming strategies. We propose implementation of a single-targeted block progression program, inspired by Newell's theoretical model of interacting constraints, may elicit positive training adaptations in a directed manner in this population. The application of Newell's theoretical model in the context of a strength and conditioning supports development of musculoskeletal properties and control and is conceptually applicable to a range of athletes.
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Affiliation(s)
- Paige E Rice
- Centre for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia.,Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, United States
| | - Sophia Nimphius
- Centre for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia.,Sports Performance Research Institute New Zealand, Auckland University of Technology, Auckland, New Zealand
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3
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Muscle alterations induced by electrostimulation are lower at short quadriceps femoris length. Eur J Appl Physiol 2019; 120:325-335. [DOI: 10.1007/s00421-019-04277-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 11/27/2019] [Indexed: 10/25/2022]
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4
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Kamandulis S, Muanjai P, Skurvydas A, Brazaitis M, Sniečkus A, Venckūnas T, Streckis V, Mickeviciene D, Jones DA. The contribution of low-frequency fatigue to the loss of quadriceps contractile function following repeated drop jumps. Exp Physiol 2019; 104:1701-1710. [PMID: 31420978 DOI: 10.1113/ep087914] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 08/15/2019] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Why do some subjects recover slowly following a bout of eccentric exercise and why is recovery faster following a repeated bout? What is the main finding and its importance? The results are consistent with two major causes of the reduction of quadriceps torque, the onset of low-frequency fatigue which recovered relatively fast and a second, delayed form of damage. Differences in the delayed damage process largely accounted for the differences in the rate of torque recovery between subjects after a first bout and it was suppression of the delayed damage which accounted for the faster recovery following a repeated bout of eccentric exercise. ABSTRACT The purpose of this study was to determine the extent to which low-frequency fatigue (LFF) accounts for the loss of quadriceps strength and time course of recovery following a series of drop jumps (DJs). Seventeen female subjects (20.8 ± 1.4 years) undertook 100 DJs, which were repeated 4 weeks later. Maximum isometric torque (MIT) and the ratio of torque generated by 20 and 100 Hz electrical stimulation (20/100), as a measure of LFF, were measured over 7 days following each series of DJs. After the first series the 20/100 ratio fell to a greater extent than MIT (to 35 ± 8.7% and 69 ± 11%, respectively) but recovered over 2-3 days, while MIT showed little recovery over this time. Changes of the 20/100 ratio were similar between subjects with fast or slow MIT recovery. Following the second series of DJs, changes in the 20/100 ratio were similar to those of the first bout and there were no differences between fast and slow recovering subjects. MIT, however, recovered more rapidly than after the first bout; the faster recovery was confined to the subjects who recovered slowly following the first bout. The results are consistent with two major causes of the reduction of quadriceps torque, the onset of low-frequency fatigue which recovered relatively fast and a second, delayed, form of damage. The latter largely accounted for the differences in MIT recovery between subjects after the first bout, while suppression of the delayed damage accounted for the faster recovery following the repeated bout.
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Affiliation(s)
- Sigitas Kamandulis
- Institute of Sport Science and Innovations, Lithuanian Sports University, Kaunas, Lithuania
| | - Pornpimol Muanjai
- Institute of Sport Science and Innovations, Lithuanian Sports University, Kaunas, Lithuania.,Department of Physical Therapy, Allied Health Sciences Faculty, Burapha University, Chonburi, Thailand
| | - Albertas Skurvydas
- Institute of Sport Science and Innovations, Lithuanian Sports University, Kaunas, Lithuania
| | - Marius Brazaitis
- Institute of Sport Science and Innovations, Lithuanian Sports University, Kaunas, Lithuania
| | - Audrius Sniečkus
- Institute of Sport Science and Innovations, Lithuanian Sports University, Kaunas, Lithuania
| | - Tomas Venckūnas
- Institute of Sport Science and Innovations, Lithuanian Sports University, Kaunas, Lithuania
| | - Vytautas Streckis
- Institute of Sport Science and Innovations, Lithuanian Sports University, Kaunas, Lithuania
| | - Dalia Mickeviciene
- Institute of Sport Science and Innovations, Lithuanian Sports University, Kaunas, Lithuania
| | - David A Jones
- School of Healthcare Science, Manchester Metropolitan University, Manchester, UK
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Lieber RL. Biomechanical response of skeletal muscle to eccentric contractions. JOURNAL OF SPORT AND HEALTH SCIENCE 2018; 7:294-309. [PMID: 30356666 PMCID: PMC6189273 DOI: 10.1016/j.jshs.2018.06.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 12/29/2017] [Accepted: 01/09/2018] [Indexed: 05/18/2023]
Abstract
The forced lengthening of an activated skeletal muscle has been termed an eccentric contraction (EC). This review highlights the mechanically unique nature of the EC and focuses on the specific disruption of proteins within the cell known as cytoskeletal proteins. The major intermediate filament cytoskeletal protein, desmin, has been the focus of work in this area because changes to desmin occur within minutes of ECs and because desmin has been shown to play both a mechanical and biologic role in a muscle's response to EC. It is hoped that these types of studies will assist in decreasing the incidence of muscle injury in athletes and facilitating the development of new therapies to treat muscle injuries.
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6
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Allen TJ, Jones T, Tsay A, Morgan DL, Proske U. Muscle damage produced by isometric contractions in human elbow flexors. J Appl Physiol (1985) 2017; 124:388-399. [PMID: 29074710 DOI: 10.1152/japplphysiol.00535.2017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Isometric exercise is often prescribed during rehabilitation from injury to maintain muscle condition and prevent disuse atrophy. However, such exercise can lead to muscle soreness and damage. Here we investigate which parameters of isometric contractions are responsible for the damage. Bouts of 30 repetitions of maximum voluntary contractions of elbow flexors in 38 subjects were carried out and peak force, soreness, and tenderness were measured before the exercise, immediately afterwards, at 2 h, and at 24 h postexercise. When one arm was held near the optimum angle for force generation (90°), the force it produced was greater by 28% than by the other arm held at a longer length (155°). However, despite the smaller contraction forces of the muscle held at the longer length, after the exercise it exhibited a greater fall in force that persisted out to 24 h (20% fall) and more delayed soreness than the muscle exercised at 90° (7% fall at 24 h). The result indicates a length dependence of the damage process for isometric contractions at maximum effort. In four additional experiments, evidence was provided that the damage occurred during the plateau of the contraction and not the rising or relaxation phases. The damage had a prompt onset and was cumulative, continuing for the duration of the contraction. We interpret our findings in terms of the nonuniform lengthening of sarcomeres during the plateau of the contractions and conclude that muscle damage from isometric exercise is minimized if carried out at lengths below the optimum, using half-maximum or smaller contractions. NEW & NOTEWORTHY Isometric exercise, where muscle contracts while the limb is held fixed, is often possible for individuals rehabilitating from injury and can help maintain muscle condition. Such exercise has been reported to cause some muscle damage and soreness. We confirm this and show that to minimize damage, exercising muscles should be held at shorter than the optimum length for force and carried out at half-maximum effort or less.
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Affiliation(s)
- Trevor J Allen
- Department of Physiology, Monash University , Clayton, Victoria , Australia
| | - Tyson Jones
- Department of Physiology, Monash University , Clayton, Victoria , Australia
| | - Anthony Tsay
- Department of Physiology, Monash University , Clayton, Victoria , Australia
| | - David L Morgan
- Department of Physiology, Monash University , Clayton, Victoria , Australia
| | - Uwe Proske
- Department of Physiology, Monash University , Clayton, Victoria , Australia
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Fatouros IG, Jamurtas AZ. Insights into the molecular etiology of exercise-induced inflammation: opportunities for optimizing performance. J Inflamm Res 2016; 9:175-186. [PMID: 27799809 PMCID: PMC5085309 DOI: 10.2147/jir.s114635] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The study of exercise-induced muscle damage (EIMD) is of paramount importance not only because it affects athletic performance but also because it is an excellent model to study the mechanisms governing muscle cachexia under various clinical conditions. Although, a large number of studies have investigated EIMD and its associated inflammatory response, several aspects of skeletal muscles responses remain unclear. In the first section of this article, the mechanisms of EIMD are reviewed in an attempt to follow the events that result in functional and structural alterations of skeletal muscle. In the second section, the inflammatory response associated with EIMD is presented with emphasis in leukocyte accumulation through mechanisms that are largely coordinated by pro- and anti-inflammatory cytokines released either by injured muscle itself or other cells. The practical applications of EIMD and the subsequent inflammatory response are discussed with respect to athletic performance. Specifically, the mechanisms leading to performance deterioration and development of muscle soreness are discussed. Emphasis is given to the factors affecting individual responses to EIMD and the resulting interindividual variability to this phenomenon.
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Affiliation(s)
- Ioannis G Fatouros
- School of Physical Education and Sport Sciences, University of Thessaly, Karies, Trikala, Greece
| | - Athanasios Z Jamurtas
- School of Physical Education and Sport Sciences, University of Thessaly, Karies, Trikala, Greece
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Joseph CW, Bradshaw EJ, Furness TP, Kemp J, Clark RA. Early changes in Achilles tendon behaviour in vivo following downhill backwards walking. J Sports Sci 2015; 34:1215-21. [PMID: 26512914 DOI: 10.1080/02640414.2015.1102955] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Downhill backwards walking causes repeated, cyclical loading of the muscle-tendon unit. The effect this type of repeated loading has on the mechanical behaviour of the Achilles tendon is presently unknown. This study aimed to investigate the biomechanical response of the Achilles tendon aponeurosis complex following a downhill backwards walking protocol. Twenty active males (age: 22.3 ± 3.0 years; mass: 74.7 ± 5.6 kg; height: 1.8 ± 0.7 m) performed 60 min of downhill (8.5°), backwards walking on a treadmill at -0.67 m · s(-1). Data were collected before, immediately post, and 24-, 48- and 168-h post-downhill backwards walking. Achilles tendon aponeurosis elongation, strain and stiffness were measured using ultrasonography. Muscle force decreased immediately post-downhill backward walking (P = 0.019). There were increases in Achilles tendon aponeurosis stiffness at 24-h post-downhill backward walking (307 ± 179.6 N · mm(-1), P = 0.004), and decreases in Achilles tendon aponeurosis strain during maximum voluntary contraction at 24 (3.8 ± 1.7%, P = 0.008) and 48 h (3.9 ± 1.8%, P = 0.002) post. Repeated cyclical loading of downhill backwards walking affects the behaviour of the muscle-tendon unit, most likely by altering muscle compliance, and these changes result in tendon stiffness increases.
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Affiliation(s)
- C W Joseph
- a Clinical Research Centre for Movement Disorders and Gait , Monash Health , Kingston , Australia.,b Australian Centre for Research into Injury in Sport and its Prevention (ACRISP) , Federation University Australia , Ballarat , Australia
| | - E J Bradshaw
- c School of Exercise Science , Australian Catholic University , Fitzroy , Australia
| | - T P Furness
- d School of Nursing, Midwifery & Paramedicine , Australian Catholic University , Fitzroy , Australia
| | - J Kemp
- c School of Exercise Science , Australian Catholic University , Fitzroy , Australia
| | - R A Clark
- c School of Exercise Science , Australian Catholic University , Fitzroy , Australia
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Mueller SM, Knechtle P, Knechtle B, Toigo M. An Ironman triathlon reduces neuromuscular performance due to impaired force transmission and reduced leg stiffness. Eur J Appl Physiol 2014; 115:795-802. [PMID: 25471270 DOI: 10.1007/s00421-014-3051-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 11/10/2014] [Indexed: 11/29/2022]
Abstract
PURPOSE An Ironman triathlon is associated with changes in body composition as well as decreases in neuromuscular function. While the changes in body composition occurring during an Ironman are well investigated, comprehensive data on the changes in neuromuscular performance are scarce. In the present study, we investigated the mechanical alterations underlying reported reductions in maximal muscular force and power after an Ironman race in men. METHODS Before and directly after an Ironman, countermovement jump (CMJ), squat jump (SJ), and multiple one-legged hopping (m1LH) maneuvers were performed to assess fatigue-related alterations in mechanical variables in thirteen male non-professional triathletes. RESULTS During CMJ, peak power (P = 0.003), peak velocity (P < 0.001), jump height (P = 0.007), and rate of force development (P = 0.042) decreased during the Ironman. Total (P < 0.001) and positive (P = 0.003) impulses during a CMJ were reduced after the triathlon, while both negative impulses did not differ pre to post Ironman. Absolute peak force remained constant during CMJ (P = 0.200) and SJ (P = 0.764). Maximal voluntary ground reaction force (F m1LH, P < 0.001) and peak stiffness (P = 0.003) during m1LH were decreased after the Ironman. CONCLUSIONS The reduced CMJ height was a result of the lower positive impulse. Therefore, the neuromuscular deficit after the Ironman race was due to impairments in force transmission, resulting in a lower average positive force during CMJ, because of a slower rate of force development. The decreased F m1LH could be partly explained by reduced leg stiffness.
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Affiliation(s)
- Sandro Manuel Mueller
- Exercise Physiology Lab, Institute of Human Movement Sciences, ETH Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
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10
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Janecki D, Jaskólska A, Marusiak J, Andrzejewska R, Jaskólski A. Twitch mechanical properties after repeated eccentric exercise of the elbow flexors. Appl Physiol Nutr Metab 2014; 39:74-81. [DOI: 10.1139/apnm-2013-0097] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Damian Janecki
- Department of Kinesiology, Faculty of Physiotherapy, University School of Physical Education, Wroclaw 51-612, Poland
| | - Anna Jaskólska
- Department of Kinesiology, Faculty of Physiotherapy, University School of Physical Education, Wroclaw 51-612, Poland
| | - Jarosław Marusiak
- Department of Kinesiology, Faculty of Physiotherapy, University School of Physical Education, Wroclaw 51-612, Poland
| | - Renata Andrzejewska
- Department of Kinesiology, Faculty of Physiotherapy, University School of Physical Education, Wroclaw 51-612, Poland
| | - Artur Jaskólski
- Department of Kinesiology, Faculty of Physiotherapy, University School of Physical Education, Wroclaw 51-612, Poland
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11
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Power GA, Dalton BH, Rice CL, Vandervoort AA. Peak power is reduced following lengthening contractions despite a maintenance of shortening velocity. Appl Physiol Nutr Metab 2013; 38:1196-205. [DOI: 10.1139/apnm-2013-0092] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Following repetitive lengthening contractions, power (the product of torque and velocity) is impaired during shortening contractions. However, the relative contribution of each component to power loss and the underlying factors are unclear. We investigated neuromuscular properties of the dorsiflexors in 8 males (27 ± 3 years) and 8 females (26 ± 4 years) for a potential sex-related difference before, during, and after 150 unaccustomed maximal lengthening actions. Velocity-dependent power was determined from shortening contractions at 8 levels (1 N·m to 70% of maximum voluntary isometric contraction (MVC)) before, after, and throughout recovery assessed at 0–30 min, 24 h, and 48 h. Immediately following task termination, both sexes displayed similar impairments of 30%, 4%, and 10% in MVC torque, shortening velocity, and overall peak power, respectively (P < 0.05). Peak rate of isometric torque development (RTD) was reduced by 10% in males, but females exhibited a 35% reduction (P < 0.05). Rate of torque development for the MVC remained depressed in both sexes throughout the 30 min recovery period; however, the RTD returned to normal by 24 h in males but did not recover by 48 h in females. Power was reduced preferentially at higher loads (i.e., 60% MVC), with a greater loss in females (65%) than males (45%). For lower loads (<20% MVC), power was impaired minimally (4%–8%; P < 0.05) and recovered within 30 min in both groups. The reduction in maximal angular velocity persisted until 30 min of recovery, and peak power did not recover until 24 h for both sexes. Unaccustomed lengthening contractions decreased power preferentially at higher loads, whereas peak power was reduced minimally owing to maintenance of maximal shortening velocity.
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Affiliation(s)
- Geoffrey A. Power
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON N6G 2M3, Canada
- Human Performance Laboratory, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - Brian H. Dalton
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON N6G 2M3, Canada
- Sensorimotor Physiology Laboratory and Human Neurophysiology Laboratory, The University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Charles L. Rice
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON N6G 2M3, Canada
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Anthony A. Vandervoort
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON N6G 2M3, Canada
- School of Physical Therapy, Faculty of Health Sciences, The University of Western Ontario, London, ON N6A 5B9, Canada
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12
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Joint angle-torque characteristics of the knee extensors following eccentric exercise-induced muscle damage in young, active women. J Exerc Sci Fit 2013. [DOI: 10.1016/j.jesf.2013.05.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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13
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Abraham AC, Kaufman KR, Donahue TLH. Phenomenological consequences of sectioning and bathing on passive muscle mechanics of the New Zealand white rabbit tibialis anterior. J Mech Behav Biomed Mater 2013; 17:290-5. [PMID: 23127626 PMCID: PMC3513661 DOI: 10.1016/j.jmbbm.2012.10.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 09/26/2012] [Accepted: 10/01/2012] [Indexed: 10/27/2022]
Abstract
Skeletal muscle tissue provides support and mobility of the musculoskeletal system. Numerical modeling of muscle tissue aids in understanding disease pathophysiology, however, the effectiveness is dependent on accurately accounting for various tissue phenomena. Muscle modeling is made difficult due to the multitude of constituents that contribute to elastic and viscous mechanisms. Often, deterministic single fiber or fiber bundle studies are undertaken to examine these contributions. However, examination of whole, intact and structurally altered tissue and comparison to findings at the myofibril scale can help elucidate tissue mechanics. Stress relaxation tests at 10% strain were performed on 28 New Zealand White rabbit's tibialis anterior muscles for whole, intact muscle and sub-sectioned muscle samples. Additionally, to aid in examining viscous effects, sub groups were tested with and without a phosphate buffered saline bath. The steady-state elastic modulus was not significantly different between groups. Interestingly, sectioning did result in a negative Poisson's ratio following tensile loading. Additionally, sectioning resulted in altering the viscous tissue response as the time to reach steady-state was significantly faster than whole muscle samples (p<0.05), as well as the linear relaxation rate from 0 to 0.1 (p<0.01), 1 to 10 (p<0.05), and 10 to 100 s (p<0.05). Bathing tissue resulted in a significantly greater amount of percent stress relaxation for whole muscle (p<0.01). These findings provide new insight into the differing mechanical characteristics of whole and sectioned muscle tissue.
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Affiliation(s)
- Adam C Abraham
- Soft Tissue Mechanics Laboratory, Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523, USA
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Power GA, Dalton BH, Rice CL, Vandervoort AA. Power loss is greater following lengthening contractions in old versus young women. AGE (DORDRECHT, NETHERLANDS) 2012; 34:737-50. [PMID: 21559865 PMCID: PMC3337924 DOI: 10.1007/s11357-011-9263-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Accepted: 04/26/2011] [Indexed: 05/13/2023]
Abstract
Compared with isometric and dynamic velocity-constrained (isokinetic) tasks, less is known regarding velocity-dependent (isotonic) muscle power and recovery in older adults following repeated fatiguing lengthening contractions. We investigated voluntary and evoked neuromuscular properties of the dorsiflexors in nine old (68.3 ± 6.1 years) and nine young women (25.1 ± 1.3 years) during and following 150 lengthening contractions for up to 30 min of recovery. At baseline, the old were ~21% weaker for maximum isometric voluntary contraction (MVC) torque (P < 0.05), ~21% slower for peak loaded shortening velocity (P < 0.05), and ~39% less powerful compared with the young (P < 0.05). Following the task, MVC torque was depressed equally (~28%) for both groups (P < 0.05), but power was reduced ~19% in the old and only ~8% in the young (P < 0.05). Both measures remained depressed during the 30-min recovery period. Peak twitch torque (P (t)) was ~50% lower in the old at task termination, whereas the young were unchanged. However, by 5 min of recovery, P (t) was reduced similarly (~50%) in both groups, and neither recovered by 30 min. The old were affected more by low-frequency torque depression than the young, as shown by the ~40% and ~20% decreases in the stimulated 10:50 Hz ratio at task termination respectively, whereas both groups were affected similarly (~50%) 5 min into recovery, and neither recovered by 30 min. Thus, the coexistence of fatigue and muscle damage induced by the repetitive lengthening contractions impaired excitation-contraction coupling and cross-bridge function to a greater extent in the old, leading to a more pronounced initial loss of power than the young for up to 10 min following the exercise However, power remained blunted in both groups during the 30-min recovery period. These results indicate that older women are more susceptible to power loss than young following lengthening contractions, likely owing to a greater impairment in calcium kinetics.
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Affiliation(s)
- Geoffrey A. Power
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON Canada
| | - Brian H. Dalton
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON Canada
| | - Charles L. Rice
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON Canada
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, ON Canada
| | - Anthony A. Vandervoort
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON Canada
- School of Physical Therapy, Faculty of Health Sciences, The University of Western Ontario, London, ON Canada
- School of Kinesiology and School of Physical Therapy, Faculty of Health Sciences, The University of Western Ontario, London, ON Canada N6G 1H1
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15
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Residual force enhancement following eccentric induced muscle damage. J Biomech 2012; 45:1835-41. [DOI: 10.1016/j.jbiomech.2012.04.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 04/05/2012] [Accepted: 04/05/2012] [Indexed: 11/22/2022]
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Skurvydas A, Brazaitis M, Venckūnas T, Kamandulis S, Stanislovaitis A, Zuoza A. The effect of sports specialization on musculus quadriceps function after exercise-induced muscle damage. Appl Physiol Nutr Metab 2011; 36:873-80. [PMID: 22050132 DOI: 10.1139/h11-112] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The primary aim of the present study was to examine the effect of eccentric exercise-induced (100 submaximal eccentric contractions at an angular velocity of 60° s⁻¹, with 20-s rest intervals) muscle damage on peripheral and central fatigue of quadriceps muscle in well-trained long-distance runners, sprint runners, volleyball players, and untrained subjects. We found that (i) indirect symptoms of exercise-induced muscle damage (prolonged decrease in maximal voluntary contraction, isokinetic concentric torque, and electrically induced (20 Hz) torque) were most evident in untrained subjects, while there were no significant differences in changes of muscle soreness and plasma creatine kinase 48 h after eccentric exercise between athletes and untrained subjects; (ii) low-frequency fatigue was greater in untrained subjects and volleyball players than in sprint runners and long-distance runners; (iii) in all subjects, electrically induced (100 Hz) torque decreased significantly by about 20%, while central activation ratio decreased significantly by about 8% in untrained subjects and sprint runners, and by about 3%-5% in long-distance runners and volleyball players. Thus, trained subjects showed greater resistance to exercise-induced muscle damage for most markers, and long-distance runners had no advantage over sprint runners or volleyball players.
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Skurvydas A, Brazaitis M, Venckūnas T, Kamandulis S. Predictive value of strength loss as an indicator of muscle damage across multiple drop jumps. Appl Physiol Nutr Metab 2011; 36:353-60. [PMID: 21574783 DOI: 10.1139/h11-023] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of the present study was to compare the time-course of indirect symptoms of exercise-induced muscle damage after 50 and 100 drop jumps. A high-force, low intensity exercise protocol was used to avoid discrepancies regarding metabolic fatigue immediately after exercise. Healthy untrained men performed 50 ("50 group", n = 13) or 100 ("100 group", n = 13) intermittent (30-s interval between each jump) drop jumps, respectively, from the height of 0.5 m with a counter-movement to a 90° knee flexion angle and immediate maximal rebound. Voluntary and electrically evoked knee extensor strength was assessed using an isokinetic dynamometer immediately before and at 2 min after exercise, as well as 3, 7, and 14 days after exercise. Creatine kinase (CK) activity and muscle soreness within 7 days after exercise were also determined. The results showed that the decrease in voluntary isometric and isokinetic torque as well as 100 Hz stimulation torque at the end of the 50 and 100 drop jumps was very similar, while substantial differences were found in low-frequency fatigue, shift in optimal knee joint angle, muscle soreness, and CK activity. In addition, there was slower muscle strength recovery after the 100 drop jumps. It is concluded that the predictive value of strength loss immediately after exercise as an indicator of muscle damage decreases as the jump number increases. Still, stimuli must be large enough for muscle torque to reach the reduction plateau. Therefore, magnitude of exercise becomes a major factor in accuracy of muscle damage predictions.
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Affiliation(s)
- Albertas Skurvydas
- Sports and Movement Science Centre, Lithuanian Academy of Physical Education, Kaunas, Lithuania
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Skurvydas A, Brazaitis M, Kamandulis S. Muscle-damaging exercise affects isokinetic torque more at short muscle length. J Strength Cond Res 2011; 25:1400-6. [PMID: 21273917 DOI: 10.1519/jsc.0b013e3181d685a0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The aim of this study was to investigate the differences in the length-dependent changes in quadriceps muscle torque during voluntary isometric and isokinetic contractions performed after severe muscle-damaging exercise. Thirteen physically active men (age = 23.8 ± 3.2 years, body weight = 77.2 ± 4.5 kg) performed stretch-shortening cycle (SSC) exercise comprising 100 drop jumps with 30-second intervals between each jump. Changes in the voluntary and electrically evoked torque in concentric and isometric conditions at different muscle lengths, muscle soreness, and plasma creatine kinase (CK) activity were assessed within 72 hours after SSC exercise. Isokinetic knee extension torque decreased significantly (p < 0.05) at all joint angles after SSC exercise. At 2 minutes and at 72 hours after SSC exercise, the changes in knee torque were significantly smaller at 80° (where 180° = full knee extension) than at 110-130°. At 2 minutes after SSC exercise, the optimal angle for isokinetic knee extension torque shifted by 9.5 ± 8.9° to a longer muscle length (p < 0.05). Electrically induced torque at low-frequency (20-Hz) stimulation decreased significantly more at a knee joint angle of 130° than at 90°. The subjects felt acute muscle pain and CK activity in the blood increased to 1,593.9 ± 536.2 IU·L⁻¹ within 72 hours after SSC exercise (p < 0.05). This study demonstrates that the effect of muscle-damaging exercise on isokinetic torque is greatest for contractions at short muscle lengths. These findings have practical importance because the movements in most physical activities are dynamic in nature, and the decrease in torque at various points in the range of motion during exercise might affect overall performance.
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Affiliation(s)
- Albertas Skurvydas
- Department of Applied Physiology and Physiotherapy, Lithuanian Academy of Physical Education, Kaunas, Lithuania.
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Piers AT, Lavin T, Radley-Crabb HG, Bakker AJ, Grounds MD, Pinniger GJ. Blockade of TNF in vivo using cV1q antibody reduces contractile dysfunction of skeletal muscle in response to eccentric exercise in dystrophic mdx and normal mice. Neuromuscul Disord 2010; 21:132-41. [PMID: 21055937 DOI: 10.1016/j.nmd.2010.09.013] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Revised: 09/22/2010] [Accepted: 09/23/2010] [Indexed: 01/25/2023]
Abstract
This study evaluated the contribution of the pro-inflammatory cytokine, tumour necrosis factor (TNF) to the severity of exercise-induced muscle damage and subsequent myofibre necrosis in mdx mice. Adult mdx and non-dystrophic C57 mice were treated with the mouse-specific TNF antibody cV1q before undergoing a damaging eccentric contraction protocol performed in vivo on a custom built mouse dynamometer. Muscle damage was quantified by (i) contractile dysfunction (initial torque deficit) immediately after the protocol, (ii) subsequent myofibre necrosis 48 h later. Blockade of TNF using cV1q significantly reduced contractile dysfunction in mdx and C57 mice compared with mice injected with the negative control antibody (cVaM) and un-treated mice. Furthermore, cV1q treatment significantly reduced myofibre necrosis in mdx mice. This in vivo evidence that cV1q reduces the TNF-mediated adverse response to exercise-induced muscle damage supports the use of targeted anti-TNF treatments to reduce the severity of the functional deficit and dystropathology in DMD.
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Affiliation(s)
- A T Piers
- School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Crawley, WA 6009, Australia
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Skurvydas A, Brazaitis M, Kamandulis S, Sipaviciene S. Peripheral and central fatigue after muscle-damaging exercise is muscle length dependent and inversely related. J Electromyogr Kinesiol 2010; 20:655-60. [DOI: 10.1016/j.jelekin.2010.02.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 02/19/2010] [Accepted: 02/22/2010] [Indexed: 12/01/2022] Open
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Power GA, Dalton BH, Rice CL, Vandervoort AA. Delayed recovery of velocity-dependent power loss following eccentric actions of the ankle dorsiflexors. J Appl Physiol (1985) 2010; 109:669-76. [PMID: 20576845 DOI: 10.1152/japplphysiol.01254.2009] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Unaccustomed eccentric exercise has been shown to impair muscle function, although little is known regarding this impairment on muscle power. The purpose of this study was to investigate changes in neuromuscular properties of the ankle dorsiflexors during and after an eccentric contraction task and throughout recovery in 21 (10 men, 11 women) recreationally active young adults (25.8+/-2.3 yr). All subjects performed 5 sets of 30 eccentric contractions at 80% of maximum isometric voluntary contraction (MVC) torque. Data were recorded at baseline, during the fatigue task, and for 30 min of recovery. There were no significant sex differences for all fatigue measures; thus data were pooled. After the fatigue task, MVC torque declined by 28% (P<0.05) and did not recover fully, and voluntary activation of the dorsiflexors, as assessed by the interpolated twitch technique, was near maximal (>99%) during and after the fatigue task (P>0.05). Peak twitch torque was reduced by 21% at 2 min of recovery and progressively decreased to 35% by 30 min (P<0.05). Low-frequency torque depression (10-to-50 Hz ratio) was present at 30 s of recovery, increased to 51% by 10 min, and did not recover fully (P<0.05). Velocity-dependent concentric power was reduced by 8% immediately after task termination and did not recover fully within 30 min (P<0.05). The main findings of an incomplete recovery of MVC torque, low-frequency torque depression, and shortening velocity indicate the presence of muscle damage, which may have altered excitation-contraction coupling and cross-bridge kinetics and reduced the number of functional sarcomeres in series, ultimately leading to velocity-dependent power loss.
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Affiliation(s)
- Geoffrey A Power
- Canadian Center for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, University of Western Ontario, London, ON, Canada N6G 1H1
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Raastad T, Owe SG, Paulsen G, Enns D, Overgaard K, Crameri R, Kiil S, Belcastro A, Bergersen L, Hallén J. Changes in calpain activity, muscle structure, and function after eccentric exercise. Med Sci Sports Exerc 2010; 42:86-95. [PMID: 20010126 DOI: 10.1249/mss.0b013e3181ac7afa] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE The aim of this study was to investigate changes in muscle function, muscle structure, and calpain activity after high-force eccentric exercise. METHODS Eleven healthy males performed 300 maximal voluntary eccentric actions with knee extensors in one leg. Maximal force-generating capacity was measured before exercise and regularly during the next 7 d. Biopsies from musculus vastus lateralis were taken in both control and exercised legs 0.5, 4, 8, 24, 96, and 168 h after exercise for evaluation of myofibrillar structure, extracellular matrix proteins, and calpain activity. RESULTS In the exercised leg, peak torque was reduced by 47 +/- 5% during exercise and was still 22 +/- 5% lower than baseline 4 d after the exercise. Calpain activity was three times higher in the exercised leg compared with the control leg 30 min after exercise. Myofibrillar disruptions were observed in 36 +/- 6% of all fibers in exercised muscle and in 2 +/- 1% of fibers in control muscle. The individual reductions in peak torque correlated with the proportion of fibers with myofibrillar disruptions (r = 0.89). The increase in calpain activity was not correlated to the proportion of fibers with myofibrillar disruptions. Nevertheless, the characteristics of the myofibrillar disruptions mimicked calpain-mediated degradation of myofibrils. Tenascin-C and the N-terminal propeptide of procollagen type III showed increased staining intensity on cross-sections 4-7 d after the exercise. CONCLUSIONS Myofibrillar disruptions seem to be a main cause for the long-lasting reduction in force-generating capacity after high-force eccentric exercise. The increase in calpain activity, but the lack of a relationship between calpain activity and the amount of muscle damage, suggests multiple roles of calpain in the damage and repair process.
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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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Kamandulis S, Skurvydas A, Brazaitis M, Škikas L, Duchateau J. The repeated bout effect of eccentric exercise is not associated with changes in voluntary activation. Eur J Appl Physiol 2009; 108:1065-74. [DOI: 10.1007/s00421-009-1219-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/18/2009] [Indexed: 12/01/2022]
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25
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Dean DM, Rago AP, Morgan JR. Fibroblast elongation and dendritic extensions in constrained versus unconstrained microtissues. ACTA ACUST UNITED AC 2009; 66:129-41. [PMID: 19170224 DOI: 10.1002/cm.20335] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Cytoskeletal tension is fundamental to many biological processes, including germ layer sorting during embryogenesis [Krieg et al., 2008]. In vitro, such tension influences cell sorting in self-assembled, 3D microtissues and can be of sufficient magnitude to cause complex-shaped microtissue failure [Dean et al., 2007]. To examine the process of failure under cell-derived tension, we subjected normal human fibroblasts (NHFs) to directed self-assembly [Dean et al., 2007] in micro-molds designed to yield self-constraining microtissues. As cells contracted in this assay, the constrained microtissues narrowed, thinned and ultimately failed at their midpoints. By adding small numbers of GFP+ cells, changes in cell movement and morphology were assessed and compared to those of unconstrained microtissues. We found that cells formed numerous dendritic extensions within an hour of self-assembly and retracted these extensions as they elongated up to 30 times their initial diameter ( approximately 600 microm) just prior to failure. Surprisingly, significant coordination in cell motility was observed over large distances within microtissues. Pharmacologic interventions showed that failure was myosin II and Rho kinase dependent and inhibition of failure resulted in shorter cells with greater numbers of extensions. These findings further our understanding of cellular self-assembly and introduce the use of GFP+ cells with directed self-assembly as a scaffold-free analogue to fibroblast-populated collagen gels (FPCGs).
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Affiliation(s)
- Dylan M Dean
- Department of Molecular Pharmacology, Physiology and Biotechnology, Center for Biomedical Engineering, Brown University, Providence, Rhode Island, USA
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Muscle damage responses of the elbow flexors to four maximal eccentric exercise bouts performed every 4 weeks. Eur J Appl Physiol 2009; 106:267-75. [PMID: 19263073 DOI: 10.1007/s00421-009-1016-7] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/12/2009] [Indexed: 10/21/2022]
Abstract
Since little is known about the repeated bout effect of more than two eccentric exercise bouts, this study compared muscle damage responses among four exercise bouts. Fifteen young (21.8 +/- 1.9 years) men performed four bouts of 30 maximal isokinetic eccentric contractions of the elbow flexors every 4 weeks. Maximal voluntary elbow flexion isometric and concentric strength, range of motion at the elbow joint (ROM), upper arm circumference, blood markers of muscle damage, and muscle soreness were measured before and up to 120 h following each bout. Changes in all measures following the second to fourth bouts were significantly (P < 0.05) smaller than those after the first bout. The decreases in strength and ROM immediately after the fourth bout were significantly (P < 0.05) smaller than other bouts. It is concluded that the first bout confers the greatest adaptation, but further adaptation is induced when the exercise is repeated more than three times.
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Changes in passive tension after stretch of unexercised and eccentrically exercised human plantarflexor muscles. Exp Brain Res 2008; 193:545-54. [DOI: 10.1007/s00221-008-1657-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Accepted: 11/12/2008] [Indexed: 10/21/2022]
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Ridgley JA, Pinniger GJ, Hamer PW, Grounds MD. The physiological effects of IGF-1 (class 1:Ea transgene) over-expression on exercise-induced damage and adaptation in dystrophic muscles of mdx mice. Pflugers Arch 2008; 457:1121-32. [DOI: 10.1007/s00424-008-0568-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Revised: 07/24/2008] [Accepted: 07/29/2008] [Indexed: 10/21/2022]
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29
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Semmler JG, Tucker KJ, Allen TJ, Proske U. Eccentric exercise increases EMG amplitude and force fluctuations during submaximal contractions of elbow flexor muscles. J Appl Physiol (1985) 2007; 103:979-89. [PMID: 17600154 DOI: 10.1152/japplphysiol.01310.2006] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to determine the effect of eccentric exercise on the ability to exert steady submaximal forces with muscles that cross the elbow joint. Eight subjects performed two tasks requiring isometric contraction of the right elbow flexors: a maximum voluntary contraction (MVC) and a constant-force task at four submaximal target forces (5, 20, 35, 50% MVC) while electromyography (EMG) was recorded from elbow flexor and extensor muscles. These tasks were performed before, after, and 24 h after a period of eccentric (fatigue and muscle damage) or concentric exercise (fatigue only). MVC force declined after eccentric exercise (45% decline) and remained depressed 24 h later (24%), whereas the reduced force after concentric exercise (22%) fully recovered the following day. EMG amplitude during the submaximal contractions increased in all elbow flexor muscles after eccentric exercise, with the greatest change in the biceps brachii at low forces (3–4 times larger at 5 and 20% MVC) and in the brachialis muscle at moderate forces (2 times larger at 35 and 50% MVC). Eccentric exercise resulted in a twofold increase in coactivation of the triceps brachii muscle during all submaximal contractions. Force fluctuations were larger after eccentric exercise, particularly at low forces (3–4 times larger at 5% MVC, 2 times larger at 50% MVC), with a twofold increase in physiological tremor at 8–12 Hz. These data indicate that eccentric exercise results in impaired motor control and altered neural drive to elbow flexor muscles, particularly at low forces, suggesting altered motor unit activation after eccentric exercise.
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Affiliation(s)
- John G Semmler
- School of Molecular and Biomedical Science, Univ. of Adelaide, Adelaide, South Australia 5005, Australia.
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