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Nuzzo JL, Pinto MD, Nosaka K. Overview of muscle fatigue differences between maximal eccentric and concentric resistance exercise. Scand J Med Sci Sports 2023; 33:1901-1915. [PMID: 37269142 DOI: 10.1111/sms.14419] [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: 03/07/2023] [Revised: 05/15/2023] [Accepted: 05/22/2023] [Indexed: 06/04/2023]
Abstract
Since the 1970s, researchers have studied a potential difference in muscle fatigue (acute strength loss) between maximal eccentric (ECCmax ) and concentric (CONmax ) resistance exercise. However, a clear answer to whether such a difference exists has not been established. Therefore, the aim of our paper was to overview methods and results of studies that compared acute changes in muscle strength after bouts of ECCmax and CONmax resistance exercise. We identified 30 relevant studies. Participants were typically healthy men aged 20-40 years. Exercise usually consisted of 40-100 isokinetic ECCmax and CONmax repetitions of the knee extensors or elbow flexors. Both ECCmax and CONmax exercise caused significant strength loss, which plateaued and rarely exceeded 60% of baseline, suggesting strength preservation. In upper-body muscles, strength loss at the end of ECCmax (31.4 ± 20.4%) and CONmax (33.6 ± 17.5%) exercise was similar, whereas in lower-body muscles, strength loss was less after ECCmax (13.3 ± 12.2%) than CONmax (39.7 ± 13.3%) exercise. Muscle architecture and daily use of lower-body muscles likely protects lower-body muscles from strength loss during ECCmax exercise. We also reviewed seven studies on muscle fatigue during coupled ECCmax -CONmax exercise and found similar strength loss in the ECC and CON phases. We also found evidence from three studies that more ECC than CON repetitions can be completed at equal relative loads. These results indicate that muscle fatigue may manifest differently between ECCmax and CONmax resistance exercise. An implication of the results is that prescriptions of ECC resistance exercise for lower-body muscles should account for greater fatigue resilience of these muscles compared to upper-body muscles.
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Affiliation(s)
- James L Nuzzo
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Australia
| | - Matheus D Pinto
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Australia
| | - Kazunori Nosaka
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Australia
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Behrens M, Gube M, Chaabene H, Prieske O, Zenon A, Broscheid KC, Schega L, Husmann F, Weippert M. Fatigue and Human Performance: An Updated Framework. Sports Med 2023; 53:7-31. [PMID: 36258141 PMCID: PMC9807493 DOI: 10.1007/s40279-022-01748-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/24/2022] [Indexed: 01/12/2023]
Abstract
Fatigue has been defined differently in the literature depending on the field of research. The inconsistent use of the term fatigue complicated scientific communication, thereby limiting progress towards a more in-depth understanding of the phenomenon. Therefore, Enoka and Duchateau (Med Sci Sports Exerc 48:2228-38, 2016, [3]) proposed a fatigue framework that distinguishes between trait fatigue (i.e., fatigue experienced by an individual over a longer period of time) and motor or cognitive task-induced state fatigue (i.e., self-reported disabling symptom derived from the two interdependent attributes performance fatigability and perceived fatigability). Thereby, performance fatigability describes a decrease in an objective performance measure, while perceived fatigability refers to the sensations that regulate the integrity of the performer. Although this framework served as a good starting point to unravel the psychophysiology of fatigue, several important aspects were not included and the interdependence of the mechanisms driving performance fatigability and perceived fatigability were not comprehensively discussed. Therefore, the present narrative review aimed to (1) update the fatigue framework suggested by Enoka and Duchateau (Med Sci Sports Exerc 48:2228-38, 2016, [3]) pertaining the taxonomy (i.e., cognitive performance fatigue and perceived cognitive fatigue were added) and important determinants that were not considered previously (e.g., effort perception, affective valence, self-regulation), (2) discuss the mechanisms underlying performance fatigue and perceived fatigue in response to motor and cognitive tasks as well as their interdependence, and (3) provide recommendations for future research on these interactions. We propose to define motor or cognitive task-induced state fatigue as a psychophysiological condition characterized by a decrease in motor or cognitive performance (i.e., motor or cognitive performance fatigue, respectively) and/or an increased perception of fatigue (i.e., perceived motor or cognitive fatigue). These dimensions are interdependent, hinge on different determinants, and depend on body homeostasis (e.g., wakefulness, core temperature) as well as several modulating factors (e.g., age, sex, diseases, characteristics of the motor or cognitive task). Consequently, there is no single factor primarily determining performance fatigue and perceived fatigue in response to motor or cognitive tasks. Instead, the relative weight of each determinant and their interaction are modulated by several factors.
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Affiliation(s)
- Martin Behrens
- Department of Sport Science, Institute III, Otto-Von-Guericke University Magdeburg, Zschokkestraße 32, 39104, Magdeburg, Germany.
- Department of Orthopedics, Rostock University Medical Center, Rostock, Germany.
| | - Martin Gube
- Department of Sport Science, University of Rostock, Rostock, Germany
| | - Helmi Chaabene
- Department of Sports and Health Sciences, Faculty of Human Sciences, University of Potsdam, Potsdam, Germany
| | - Olaf Prieske
- Division of Exercise and Movement, University of Applied Sciences for Sports and Management Potsdam, Potsdam, Germany
| | - Alexandre Zenon
- Institut de Neurosciences Cognitives et Intégratives d'Aquitaine (INCIA)-UMR 5287, CNRS, University of Bordeaux, Bordeaux, France
| | - Kim-Charline Broscheid
- Department of Sport Science, Institute III, Otto-Von-Guericke University Magdeburg, Zschokkestraße 32, 39104, Magdeburg, Germany
| | - Lutz Schega
- Department of Sport Science, Institute III, Otto-Von-Guericke University Magdeburg, Zschokkestraße 32, 39104, Magdeburg, Germany
| | | | - Matthias Weippert
- Department of Sport Science, University of Rostock, Rostock, Germany
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Performance fatigability during isometric vs. concentric quadriceps fatiguing tasks in men and women. J Electromyogr Kinesiol 2022; 67:102715. [PMID: 36274441 DOI: 10.1016/j.jelekin.2022.102715] [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: 07/01/2022] [Revised: 09/13/2022] [Accepted: 10/10/2022] [Indexed: 12/12/2022] Open
Abstract
In the present study, we aimed to provide a robust comparison of the fatigability of the knee extensors following isometric (ISO) and concentric (CON) tasks. Twenty young adults (25 ± 4 yr, 10 women) randomly performed the ISO and CON quadriceps intermittent fatigue test, consisting of ten (5 s on/5-s off, ISO) or one-hundred (0.5-s on/0.5-s off, CON) contractions with 10 % increments per stage until exhaustion. Performance fatigability was quantified as maximal isometric (MVIC) and concentric (MVCC) torque loss. Voluntary activation and contractile function (peak-twitch) were investigated using peripheral nerve stimulation. Number of stages (6.2 ± 0.7 vs. 4.9 ± 0.8; P < 0.001) and torque-time integral (20,166 ± 7,821 vs. 11,285 ± 4,933 Nm.s; P < 0.001) were greater for ISO than CON. MVIC, MVCC and voluntary activation decreased similarly between sessions (P > 0.05) whereas peak-twitch amplitude decreased more for CON (P < 0.001). The number of contractions was similar across sexes (ISO: men = 62 ± 8, women = 61 ± 5; CON: men = 521 ± 67, women = 458 ± 76, P > 0.05). MVCC was more reduced in women for both sessions (all P < 0.05), while MVIC loss was similar between sexes. We concluded that, despite greater torque-time integral and duration for ISO, both sessions induced a similar performance fatigability at exhaustion. Contractile function was more altered in CON. Finally, sex-related difference in fatigability depends on the contraction mode used during testing.
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O'Bryan SJ, Taylor JL, D'Amico JM, Rouffet DM. Quadriceps Muscle Fatigue Reduces Extension and Flexion Power During Maximal Cycling. Front Sports Act Living 2022; 3:797288. [PMID: 35072064 PMCID: PMC8777021 DOI: 10.3389/fspor.2021.797288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 12/03/2021] [Indexed: 11/13/2022] Open
Abstract
Purpose: To investigate how quadriceps muscle fatigue affects power production over the extension and flexion phases and muscle activation during maximal cycling.Methods: Ten participants performed 10-s maximal cycling efforts without fatigue and after 120 bilateral maximal concentric contractions of the quadriceps muscles. Extension power, flexion power and electromyographic (EMG) activity were compared between maximal cycling trials. We also investigated the associations between changes in quadriceps force during isometric maximal voluntary contractions (IMVC) and power output (flexion and extension) during maximal cycling, in addition to inter-individual variability in muscle activation and pedal force profiles.Results: Quadriceps IMVC (−52 ± 21%, P = 0.002), voluntary activation (−24 ± 14%, P < 0.001) and resting twitch amplitude (−45 ± 19%, P = 0.002) were reduced following the fatiguing task, whereas vastus lateralis (P = 0.58) and vastus medialis (P = 0.15) M-wave amplitudes were unchanged. The reductions in extension power (−15 ± 8%, P < 0.001) and flexion power (−24 ± 18%, P < 0.001) recorded during maximal cycling with fatigue of the quadriceps were dissociated from the decreases in quadriceps IMVC. Peak EMG decreased across all muscles while inter-individual variability in pedal force and EMG profiles increased during maximal cycling with quadriceps fatigue.Conclusion: Quadriceps fatigue induced by voluntary contractions led to reduced activation of all lower limb muscles, increased inter-individual variability and decreased power production during maximal cycling. Interestingly, power production was further reduced over the flexion phase (24%) than the extension phase (15%), likely due to larger levels of peripheral fatigue developed in RF muscle and/or a higher contribution of the quadriceps muscle to flexion power production compared to extension power during maximal cycling.
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Affiliation(s)
- Steven J. O'Bryan
- Institute for Health and Sport (IHeS), Victoria University, Melbourne, VIC, Australia
| | - Janet L. Taylor
- Neuroscience Research Australia, Randwick, NSW, Australia
- School of Medical and Health Sciences, Edith Cowan University, Perth, WA, Australia
| | - Jessica M. D'Amico
- Department of Neurological Surgery, University of Louisville, Louisville, KY, United States
- Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, KY, United States
| | - David M. Rouffet
- Institute for Health and Sport (IHeS), Victoria University, Melbourne, VIC, Australia
- Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, KY, United States
- Department of Health and Sport Sciences, University of Louisville, Louisville, KY, United States
- *Correspondence: David M. Rouffet
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Fatigue Measured in Dynamic Versus Isometric Modes After Trail Running Races of Various Distances. Int J Sports Physiol Perform 2021; 17:67-77. [PMID: 34359049 DOI: 10.1123/ijspp.2020-0940] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 04/14/2021] [Accepted: 05/03/2021] [Indexed: 11/18/2022]
Abstract
PURPOSE Fatigue has previously been investigated in trail running by comparing maximal isometric force before and after the race. Isometric contractions may not entirely reflect fatigue-induced changes, and therefore dynamic evaluation is warranted. The aim of the present study was to compare the magnitude of the decrement of maximal isometric force versus maximal power, force, and velocity after trail running races ranging from 40 to 170 km. METHODS Nineteen trail runners completed races shorter than 60 km, and 21 runners completed races longer than 100 km. Isometric maximal voluntary contractions (IMVCs) of knee extensors and plantar flexors and maximal 7-second sprints on a cycle ergometer were performed before and after the event. RESULTS Maximal power output (Pmax; -14% [11%], P < .001), theoretical maximum force (F0; -11% [14%], P < .001), and theoretical maximum velocity (-3% [8%], P = .037) decreased significantly after both races. All dynamic parameters but theoretical maximum velocity decreased more after races longer than 100 km than races shorter than 60 km (P < .05). Although the changes in IMVCs were significantly correlated (P < .05) with the changes in F0 and Pmax, reductions in IMVCs for knee extensors (-29% [16%], P < .001) and plantar flexors (-26% [13%], P < .001) were larger (P < .001) than the reduction in Pmax and F0. CONCLUSIONS After a trail running race, reductions in isometric versus dynamic forces were correlated, yet they are not interchangeable because the losses in isometric force were 2 to 3 times greater than the reductions in Pmax and F0. This study also shows that the effect of race distance on fatigue measured in isometric mode is true when measured in dynamic mode.
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Rodriguez-Lopez C, Alcazar J, Losa-Reyna J, Carmona-Torres J, Cruz-Santaella AM, Ara I, Csapo R, Alegre LM. Acute Physiological Response to Light- and Heavy-load Power-oriented Exercise in Older Adults. Int J Sports Med 2021; 42:1287-1296. [PMID: 33902152 DOI: 10.1055/a-1408-4793] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
This study investigated the acute responses to volume-load-matched heavy-load (80% 1RM) versus light-load (40% 1RM) power-oriented resistance training sessions in well-functioning older adults. Using a randomized cross-over design, 15 volunteers completed each condition on a leg press. Neuromuscular (maximal isometric force and rate of force development) and functional performance (power during sit-to-stand test), lactate, and muscle damage biochemistry (creatine kinase, lactate dehydrogenase and C-reactive protein serum concentration) were assessed pre- and post-exercise. Performance declines were found after heavy-load (Cohen's d effect size (d); maximal isometric force=0.95 d; rate of force development=1.17 d; sit-to-stand power =0.38 d, all p<0.05) and light-load (maximal isometric force=0.45 d; rate of force development=0.9 d; sit-to-stand power=1.17 d, all p<0.05), while lactate concentration increased only after light-load (1.7 d, p=0.001). However, no differences were found between conditions (all p>0.05). Both conditions increased creatine kinase the day after exercise (marginal effect=0.75 d, p<0.001), but no other blood markers increased (all, p>0.05). Irrespective of the load used, power training induced non-clinically significant decreases in sit-to-stand performance, moderate declines in maximal isometric force, but pronounced decreases in the rate of force development. Furthermore, the metabolic stress and muscle damage were minor; both sessions were generally well tolerated by well-functioning older adults without previous experience in resistance training.
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Affiliation(s)
- Carlos Rodriguez-Lopez
- GENUD Toledo Research Group, Universidad de Castilla-La Mancha, Toledo, Spain.,CIBER of Frailty and Healthy Aging (CIBERFES), Madrid, Spain
| | - Julian Alcazar
- GENUD Toledo Research Group, Universidad de Castilla-La Mancha, Toledo, Spain.,CIBER of Frailty and Healthy Aging (CIBERFES), Madrid, Spain
| | - Jose Losa-Reyna
- GENUD Toledo Research Group, Universidad de Castilla-La Mancha, Toledo, Spain.,CIBER of Frailty and Healthy Aging (CIBERFES), Madrid, Spain.,Department of Geriatrics, Hospital Virgen del Valle, Complejo Hospitalario de Toledo, Toledo, Spain
| | | | | | - Ignacio Ara
- CIBER of Frailty and Healthy Aging (CIBERFES), Madrid, Spain.,CIBER of Frailty and Healthy Aging (CIBERFES), Madrid, Spain
| | - Robert Csapo
- Research Unit for Orthopaedic Sports Medicine and Injury Prevention, ISAG, University for Health Sciences, Medical Informatics and Technology, Hall in Tirol, Austria
| | - Luis M Alegre
- GENUD Toledo Research Group, Universidad de Castilla-La Mancha, Toledo, Spain.,CIBER of Frailty and Healthy Aging (CIBERFES), Madrid, Spain
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Rivière JR, Peyrot N, Cross MR, Messonnier LA, Samozino P. Strength-Endurance: Interaction Between Force-Velocity Condition and Power Output. Front Physiol 2020; 11:576725. [PMID: 33162900 PMCID: PMC7583360 DOI: 10.3389/fphys.2020.576725] [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: 06/26/2020] [Accepted: 09/04/2020] [Indexed: 11/13/2022] Open
Abstract
Context Strength-endurance mainly depends on the power output, which is often expressed relative to the individual’s maximal power capability (Pmax). However, an individual can develop the same power, but in different combinations of force and velocity (force-velocity condition). Also, at matched power output, changing the force-velocity condition results in a change of the velocity-specific relative power (Pmaxv), associated with a change in the power reserve. So far, the effect of these changing conditions on strength-endurance remains unclear. Purpose We aimed to test the effects of force-velocity condition and power output on strength-endurance. Methods Fourteen sportsmen performed (i) force- and power-velocity relationships evaluation in squat jumps and (ii) strength-endurance evaluations during repeated squat jump tests in 10 different force-velocity-power conditions, individualized based on the force- and power-velocity relationships. Each condition was characterized by different (i) relative power (%Pmax), (ii) velocity-specific relative power (%Pmaxv), and (iii) ratio between force and velocity (RFv). Strength-endurance was assessed by the maximum repetitions (SJRep), and the cumulated mechanical work (Wtot) performed until exhaustion during repeated squat jump tests. Intra and inter-day reliability of SJRep were tested in one of the 10 conditions. The effects of %Pmax, %Pmaxv, and RFv on SJRep and Wtot were tested via stepwise multiple linear regressions and two-way ANOVAs. Results SJRep exhibited almost perfect intra- and inter-day reliability (ICC=0.94 and 0.92, respectively). SJRep and Wtot were influenced by %Pmaxv and RFv (R2 = 0.975 and 0.971; RSME=0.243 and 0.234, respectively; both p < 0.001), with the effect of RFv increasing with decreasing %Pmaxv (interaction effect, p = 0.03). %Pmax was not considered as a significant predictor of strength-endurance by the multiple regressions analysis. SJRep and Wtot were higher at lower %Pmaxv and in low force-high velocity conditions (i.e., lower RFv). Conclusion Strength-endurance was almost fully dependent on the position of the exercise conditions relative to the individual force-velocity and power-velocity relationships (characterized by %Pmaxv and RFv). Thus, the standardization of the force-velocity condition and the velocity-specific relative power should not be overlooked for strength-endurance testing and training, but also when setting fatiguing protocols.
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Affiliation(s)
- Jean Romain Rivière
- Univ Savoie Mont Blanc, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, Chambéry, France
| | - Nicolas Peyrot
- Le Mans Université, Movement-Interactions-Performance, MIP, EA 4334, Le Mans, France
| | - Matthew R Cross
- Univ Savoie Mont Blanc, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, Chambéry, France
| | - Laurent A Messonnier
- Univ Savoie Mont Blanc, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, Chambéry, France
| | - Pierre Samozino
- Univ Savoie Mont Blanc, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, Chambéry, France
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Morel B, Lapole T, Liotard C, Hautier C. Critical Peripheral Fatigue Thresholds Among Different Force-Velocity Conditions: An Individual-Based Model Approach. Front Physiol 2019; 10:875. [PMID: 31379595 PMCID: PMC6646582 DOI: 10.3389/fphys.2019.00875] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Accepted: 06/21/2019] [Indexed: 01/24/2023] Open
Abstract
During high intensity exercise, metabosensitive muscle afferents are thought to inhibit the motor drive command to restrict the level of peripheral fatigue to an individual's critical threshold. No evidence exists of an individual relationship between peripheral fatigue and the decrease in voluntary activation reached after prolonged all-out exercise. Moreover, there is no explanation for the previously reported large decrease in voluntary activation despite low metabolic stress during high force contractions. Thirteen active men completed two maximal intensity isokinetic knee extension tests (160 contractions) under conditions of low force - high velocity and high force - low velocity. Neuromuscular testing including maximal torque, evoked torque and voluntary activation, was done every 20 contractions. The exponential modeling of these variables over time allowed us to predict the stable state (asymptote) and the rate of decrease (curvature constant). For both high and low force contractions the evoked torque and voluntary activation asymptotes were negatively correlated (R 2 = 0.49 and R 2 = 0.46, respectively). The evoked torque asymptotes of the high and low force conditions were positively correlated (R 2 = 0.49). For the high force contractions, the evoked torque and voluntary activation curvature constant were negatively correlated (R 2 = 0.43). These results support the idea that a restrained central motor drive keeps peripheral fatigue under this threshold. Furthermore, an individual would show similar fatigue sensibility regardless of the force generated. These data also suggest that the decrease in voluntary activation might not have been triggered by peripheral perturbations during the first high force contractions.
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Affiliation(s)
- Baptiste Morel
- EA 7424, F-42023, Laboratoire Interuniversitaire de Biologie de la Motricité, Universite de Lyon, Université Jean Monnet Saint-Étienne, Saint-Étienne, France.,Movement-Interactions-Performance, MIP, EA 4334, F-72000, Le Mans Université, Le Mans, France
| | - Thomas Lapole
- EA 7424, F-42023, Laboratoire Interuniversitaire de Biologie de la Motricité, Universite de Lyon, Université Jean Monnet Saint-Étienne, Saint-Étienne, France
| | - Cyril Liotard
- EA 7424, F-42023, Laboratoire Interuniversitaire de Biologie de la Motricité, Universite de Lyon, Université Jean Monnet Saint-Étienne, Saint-Étienne, France
| | - Christophe Hautier
- EA7424, Laboratoire Interuniversitaire de Biologie de la Motricité, Université Claude Bernard Lyon 1, Villeurbanne, France
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Krüger RL, Aboodarda SJ, Jaimes LM, Samozino P, Millet GY. Cycling performed on an innovative ergometer at different intensities-durations in men: neuromuscular fatigue and recovery kinetics. Appl Physiol Nutr Metab 2019; 44:1320-1328. [PMID: 31082324 DOI: 10.1139/apnm-2018-0858] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The majority of studies have routinely measured neuromuscular (NM) fatigue with a delay (∼1-3 min) after cycling exercises. This is problematic since NM fatigue can massively recover within the first 1-2 min after exercise. This study investigated the etiology of knee extensors (KE) NM fatigue and recovery kinetics in response to cycling exercises by assessing NM function as early as 10 s following cycling and up to 8 min of recovery. Ten young males performed different cycling exercises on different days: a Wingate (WING), a 10-min task at severe-intensity (SEV), and a 90-min task at moderate-intensity (MOD). Electrically evoked and isometric maximal voluntary contractions (IMVC) of KE were assessed before, after, and during recovery. SEV induced the highest decrease in IMVC. Peak twitch (Pt) was more reduced in WING and SEV than in MOD (p < 0.001), whereas voluntary activation decreased more after MOD than WING (p = 0.043). Regarding Pt and the ratio between low- and high-frequency doublet (i.e., low-frequency fatigue), recovery was faster for WING, whereas IMVC and high-frequency doublet recovered slower during MOD (p < 0.05). Our results confirm that peripheral fatigue is greater after WING and SEV, while central fatigue is greater following MOD. Peripheral fatigue can substantially recover within minutes after a supramaximal exercise while NM function recovered slower after prolonged, moderate-intensity exercise. This study provides an accurate estimation of NM fatigue and recovery kinetics because of dynamic exercise with large muscle mass by significantly shortening the delay for postexercise measurements.
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Affiliation(s)
- Renata L Krüger
- The Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - Saied Jalal Aboodarda
- The Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - Libia Marcela Jaimes
- The Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - Pierre Samozino
- The University of Savoie Mont Blanc, Inter-university Laboratory of Human Movement Sciences, EA 7424, F-73000 Chambéry, France
| | - Guillaume Y Millet
- The Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB T2N 1N4, Canada
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Abstract
The purpose of this study was to compare the effects of unilateral ankle fatigue versus the knee muscles with and without vision on bipedal postural control. Elite judo athletes who competed at the national level with at least 10 years of training experience, were randomised into KNEE (n = 10; 20 ± 2 years) and ANKLE (n = 9; 20 ± 3 years) groups, who performed dynamic isokinetic fatiguing contractions (force decreased to 50% of initial peak torque for three consecutive movements) of the knee flexors and extensors or ankle dorsiflexors and plantar flexors, respectively. Static bipedal postural control (French Posturology Association normative standards) with eyes open and eyes closed was examined before and immediately after the fatiguing task. Postural variables examined were the centre of pressure (CoP) sway in the medio-lateral and antero-posterior directions, total CoP area sway and CoP sway velocity. Although unilateral ankle and knee fatigue adversely affected all bipedal postural measures, with greater disturbances with eyes closed, there were no significant main group or interaction effects between KNEE and ANKLE groups. Unilateral lower limb fatigue adversely affected bipedal balance, with knee extension/flexion fatigue affecting bipedal postural control to a similar extent as unilateral ankle dorsiflexion/plantar flexion fatigue. Hence unilateral fatigue can affect subsequent bilateral performance or also have implications for rehabilitation exercise techniques. Our findings may be limited to judo athletes as other populations were not tested.
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Aboodarda SJ, Fan S, Coates K, Millet GY. The short-term recovery of corticomotor responses in elbow flexors. BMC Neurosci 2019; 20:9. [PMID: 30871475 PMCID: PMC6419454 DOI: 10.1186/s12868-019-0492-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 03/06/2019] [Indexed: 11/10/2022] Open
Abstract
Background The recovery of neurophysiological parameters at various time intervals following fatiguing exercise has been investigated previously. However, the repetition of neuromuscular assessments during the recovery period may have interfered with the true corticomotor excitability responses. In this experiment, fatiguing contractions were combined with a single post-fatigue assessment at varying time points. Ten participants undertook 5 bouts of 60-s maximal voluntary contractions (MVC) of the elbow flexors, separated by 20 min. Before and after each 60-s fatiguing exercise (FAT), participants performed a series of 6-s contractions at 100, 75 and 50% of their MVC during which transcranial magnetic, transmastoid electrical and brachial plexus electrical stimuli were used to elicit motor evoked potentials (MEP), cervicomedullary motor evoked potentials (CMEP) and compound muscle action potentials (Mmax) in the biceps brachii muscle, respectively. Post-FAT measurements were randomly performed 0, 15, 30, 60, or 120 s after each FAT. Results MVC force declined to 65.1 ± 13.1% of baseline following FAT and then recovered to 82.7 ± 10.2% after 60 s. The MEP·Mmax−1 ratio recorded at MVC increased to 151.1 ± 45.8% and then returned to baseline within 60 s. The supraspinal excitability (MEP·CMEP−1) measured at MVC increased to 198.2 ± 47.2% and fully recovered after 30 s. The duration of post-MEP silent period recorded at MVC elongated by 23.4 ± 10.6% during FAT (all P < 0.05) but fully recovered after 15 s. Conclusions The current study represents the first accurate description of the time course and pattern of recovery for supraspinal and spinal excitability and inhibition following a short maximal fatiguing exercise in upper limb.
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Affiliation(s)
- Saied Jalal Aboodarda
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Dr NW, Calgary, AB, T2N 1N4, Canada
| | - Selina Fan
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Dr NW, Calgary, AB, T2N 1N4, Canada
| | - Kyla Coates
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Dr NW, Calgary, AB, T2N 1N4, Canada
| | - Guillaume Y Millet
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Dr NW, Calgary, AB, T2N 1N4, Canada.
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A phenomenological model of the time course of maximal voluntary isometric contraction force for optimization of complex loading schemes. Eur J Appl Physiol 2018; 118:2587-2605. [DOI: 10.1007/s00421-018-3983-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Accepted: 08/29/2018] [Indexed: 10/28/2022]
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13
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Penasso H, Thaller S. Model-based analysis of fatigued human knee extensors : Effects of isometrically induced fatigue on Hill-type model parameters and ballistic contractions. Eur J Appl Physiol 2018; 118:1447-1461. [PMID: 29730804 PMCID: PMC6028922 DOI: 10.1007/s00421-018-3875-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 04/23/2018] [Indexed: 02/05/2023]
Abstract
This study investigated the effect of isometrically induced fatigue on Hill-type muscle model parameters and related task-dependent effects. Parameter identification methods were used to extract fatigue-related parameter trends from isometric and ballistic dynamic maximum voluntary knee extensions. Nine subjects, who completed ten fatiguing sets, each consisting of nine 3 s isometric maximum voluntary contractions with 3 s rest plus two ballistic contractions with different loads, were analyzed. Only at the isometric task, the identified optimized model parameter values of muscle activation rate and maximum force generating capacity of the contractile element decreased from [Formula: see text] to [Formula: see text] Hz and from [Formula: see text] to [Formula: see text] N, respectively. For all tasks, the maximum efficiency of the contractile element, mathematically related to the curvature of the force-velocity relation, increased from [Formula: see text] to [Formula: see text]. The model parameter maximum contraction velocity decreased from [Formula: see text] to [Formula: see text] m/s and the stiffness of the serial elastic element from [Formula: see text] to [Formula: see text] N/mm. Thus, models of fatigue should consider fatigue dependencies in active as well as in passive elements, and muscle activation dynamics should account for the task dependency of fatigue.
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Affiliation(s)
- Harald Penasso
- Institute of Sport Science, University of Graz, Mozartgasse 14, 8010, Graz, Austria.
| | - Sigrid Thaller
- Institute of Sport Science, University of Graz, Mozartgasse 14, 8010, Graz, Austria
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14
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Cross MR, Brughelli M, Samozino P, Morin JB. Methods of Power-Force-Velocity Profiling During Sprint Running: A Narrative Review. Sports Med 2018; 47:1255-1269. [PMID: 27896682 DOI: 10.1007/s40279-016-0653-3] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The ability of the human body to generate maximal power is linked to a host of performance outcomes and sporting success. Power-force-velocity relationships characterize limits of the neuromuscular system to produce power, and their measurement has been a common topic in research for the past century. Unfortunately, the narrative of the available literature is complex, with development occurring across a variety of methods and technology. This review focuses on the different equipment and methods used to determine mechanical characteristics of maximal exertion human sprinting. Stationary cycle ergometers have been the most common mode of assessment to date, followed by specialized treadmills used to profile the mechanical outputs of the limbs during sprint running. The most recent methods use complex multiple-force plate lengths in-ground to create a composite profile of over-ground sprint running kinetics across repeated sprints, and macroscopic inverse dynamic approaches to model mechanical variables during over-ground sprinting from simple time-distance measures during a single sprint. This review outlines these approaches chronologically, with particular emphasis on the computational theory developed and how this has shaped subsequent methodological approaches. Furthermore, training applications are presented, with emphasis on the theory underlying the assessment of optimal loading conditions for power production during resisted sprinting. Future implications for research, based on past and present methodological limitations, are also presented. It is our aim that this review will assist in the understanding of the convoluted literature surrounding mechanical sprint profiling, and consequently improve the implementation of such methods in future research and practice.
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Affiliation(s)
- Matt R Cross
- Sports Performance Research Institute New Zealand (SPRINZ), Auckland University of Technology, Auckland, New Zealand.
| | - Matt Brughelli
- Sports Performance Research Institute New Zealand (SPRINZ), Auckland University of Technology, Auckland, New Zealand
| | - Pierre Samozino
- Inter-University Laboratory of Human Movement Biology, University Savoie Mont Blanc, Le Bourget-du-Lac, France
| | - Jean-Benoit Morin
- Sports Performance Research Institute New Zealand (SPRINZ), Auckland University of Technology, Auckland, New Zealand.,Université Côte d'Azur, LAMHESS, Nice, France
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15
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Pinto MD, Blazevich AJ, Andersen LL, Mil-Homens P, Pinto RS. Hamstring-to-quadriceps fatigue ratio offers new and different muscle function information than the conventional non-fatigued ratio. Scand J Med Sci Sports 2017; 28:282-293. [DOI: 10.1111/sms.12891] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/31/2017] [Indexed: 01/13/2023]
Affiliation(s)
- M. D. Pinto
- Exercise Research Laboratory; Strength Training Research Group; Federal University of Rio Grande do Sul; Porto Alegre RS Brazil
- Centre for Exercise and Sports Science Research; School of Medical and Health Sciences; Edith Cowan University; Joondalup WA Australia
| | - A. J. Blazevich
- Centre for Exercise and Sports Science Research; School of Medical and Health Sciences; Edith Cowan University; Joondalup WA Australia
| | - L. L. Andersen
- National Research Centre for the Working Environment; Copenhagen Denmark
- Physical Activity and Human Performance group; SMI; Department of Health Science and Technology; Aalborg University; Aalborg Denmark
| | - P. Mil-Homens
- CIPER; Faculdade de Motricidade Humana; Universidade de Lisboa; Cruz Quebrada Portugal
| | - R. S. Pinto
- Exercise Research Laboratory; Strength Training Research Group; Federal University of Rio Grande do Sul; Porto Alegre RS Brazil
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16
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Miranda H, Maia M, de Oliveira CG, Farias D, da Silva JB, Lima VP, Willardson JM, Paz GA. Myoeletric indices of fatigue adopting different rest intervals during leg press sets. J Bodyw Mov Ther 2017; 22:178-183. [PMID: 29332743 DOI: 10.1016/j.jbmt.2017.03.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
INTRODUCTION The purpose of this study was to examine the acute effect of different rest intervals between multiple sets of the 45° angled leg press exercise (LP45) on surface electromyographic (SEMG) spectral and amplitude indices of fatigue. METHODS Fifteen recreationally trained females performed three protocols in a randomized crossover design; each consisting of four sets of 10 repetitions with 1 (P1), 3 (P3), or 5 (P5) minute rest intervals between sets. Each set was performed with 70% of the LP45 ten-repetition maximum load. The SEMG data for biceps femoris (BF), vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) muscles was then evaluated. RESULTS The SEMG amplitude change in the time coefficient (CRMS) and spectral fatigue index (Cf5) indicated higher levels of fatigue for all muscles evaluated during the P3 protocol versus the P1 and P5 protocols (p ≤ 0.05), respectively. The RF and VL muscles showed greater fatigue levels by the second and third sets; whereas, greater fatigue was shown in the VM and BF muscles by the fourth set (p ≤ 0.05). CONCLUSIONS A three-minute rest interval between sets might represent a neuromuscular window between a fatigue stated and fully recovered state in the context of neural activation. Moreover, a three minute rest interval between sets might allow for consistent recruitment of high threshold motor units over multiple sets, and thus promote a more effective stimulus for strength gains.
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Affiliation(s)
- Humberto Miranda
- School of Physical Education and Sports, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Marianna Maia
- School of Physical Education and Sports, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; Biodynamic Laboratory of Exercise, Health and Performance, Castelo Branco University, Rio de Janeiro, Brazil; Biodesp Institute, Kinesiology Center of Performance, Rio de Janeiro, Brazil
| | - Carlos G de Oliveira
- School of Physical Education and Sports, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Déborah Farias
- School of Physical Education and Sports, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Jurandir B da Silva
- School of Physical Education and Sports, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
| | - Vicente P Lima
- Biodynamic Laboratory of Exercise, Health and Performance, Castelo Branco University, Rio de Janeiro, Brazil; Biodesp Institute, Kinesiology Center of Performance, Rio de Janeiro, Brazil; Institute of Physical Education and Sports, Postgraduate Program in Exercise and Sport Sciences, State University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Jeffrey M Willardson
- Department of Health and Human Performance, Rocky Mountain College, Billings, MT, United States
| | - Gabriel A Paz
- School of Physical Education and Sports, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; Biodynamic Laboratory of Exercise, Health and Performance, Castelo Branco University, Rio de Janeiro, Brazil; Biodesp Institute, Kinesiology Center of Performance, Rio de Janeiro, Brazil
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17
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Prieske O, Aboodarda SJ, Benitez Sierra JA, Behm DG, Granacher U. Slower but not faster unilateral fatiguing knee extensions alter contralateral limb performance without impairment of maximal torque output. Eur J Appl Physiol 2017; 117:323-334. [PMID: 28078451 DOI: 10.1007/s00421-016-3524-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 12/20/2016] [Indexed: 01/07/2023]
Abstract
PURPOSE The purpose of the present study was to examine the effects of unilateral fatigue of the knee extensors at different movement velocities on neuromuscular performance in the fatigued and non-fatigued leg. METHODS Unilateral fatigue of the knee extensors was induced in 11 healthy young men (23.7 ± 3.8 years) at slower (60°/s; FAT60) and faster movement velocities (240°/s; FAT240) using an isokinetic dynamometer. A resting control (CON) condition was included. The fatigue protocols consisted of five sets of 15 maximal concentric knee extensions using the dominant leg. Before and after fatigue, peak isokinetic torque (PIT) and time to PIT (TTP) of the knee extensors as well as electromyographic (EMG) activity of vastus medialis, vastus lateralis, and biceps femoris muscles were assessed at 60 and 240°/s movement velocities in the fatigued and non-fatigued leg. RESULTS In the fatigued leg, significantly greater PIT decrements were observed following FAT60 and FAT240 (11-19%) compared to CON (3-4%, p = .002, d = 2.3). Further, EMG activity increased in vastus lateralis and biceps femoris muscle following FAT240 only (8-28%, 0.018 ≤ p ≤ .024, d = 1.8). In the non-fatigued leg, shorter TTP values were found after the FAT60 protocol (11-15%, p = .023, d = 2.4). No significant changes were found for EMG data in the non-fatigued leg. CONCLUSION The present study revealed that both slower and faster velocity fatiguing contractions failed to show any evidence of cross-over fatigue on PIT. However, unilateral knee extensor fatigue protocols conducted at slower movement velocities (i.e., 60°/s) appear to modulate torque production on the non-fatigued side (evident in shorter TTP values).
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Affiliation(s)
- Olaf Prieske
- Division of Training and Movement Science, Research Focus Cognition Sciences, University of Potsdam, Am Neuen Palais 10, Building 12, 14469, Potsdam, Germany.
| | | | - José A Benitez Sierra
- Division of Training and Movement Science, Research Focus Cognition Sciences, University of Potsdam, Am Neuen Palais 10, Building 12, 14469, Potsdam, Germany
| | - David G Behm
- School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NF, Canada
| | - Urs Granacher
- Division of Training and Movement Science, Research Focus Cognition Sciences, University of Potsdam, Am Neuen Palais 10, Building 12, 14469, Potsdam, Germany
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Smith CM, Housh TJ, Herda TJ, Zuniga JM, Camic CL, Bergstrom HC, Smith DB, Weir JP, Hill EC, Cochrane KC, Jenkins NDM, Schmidt RJ, Johnson GO. Time Course of Changes in Neuromuscular Parameters During Sustained Isometric Muscle Actions. J Strength Cond Res 2016; 30:2697-2702. [PMID: 27658233 DOI: 10.1519/jsc.0000000000001547] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Smith, CM, Housh, TJ, Herda, TJ, Zuniga, JM, Camic, CL, Bergstrom, HC, Smith, DB, Weir, JP, Hill, EC, Cochrane, KC, Jenkins, NDM, Schmidt, RJ, and Johnson, GO. Time course of changes in neuromuscular parameters during sustained isometric muscle actions. J Strength Cond Res 30(10): 2697-2702, 2016-The objective of the present study was to identify the time course of changes in electromyographic (EMG) and mechanomyographic (MMG) time and frequency domain parameters during a sustained isometric muscle action of the leg extensors at 50% maximal voluntary isometric contraction. The EMG and MMG signals were measured from the vastus lateralis of 11 subjects to identify when motor unit activation strategies changed throughout the sustained isometric muscle action. The EMG amplitude (muscle activation) had a positive linear relationship (p = 0.018, r = 0.77) that began to increase at the initiation of the muscle action and continued until task failure. Electromyographic frequency (motor unit action potential conduction velocity) and MMG frequency (global motor unit firing rate) had negative quadratic relationships (p = 0.002, R = 0.99; p = 0.015, R = 0.94) that began to decrease at 30% of the time to exhaustion. The MMG amplitude (motor unit activation) had a cubic relationship (p = 0.001, R = 0.94) that increased from 10 to 30% of the time to exhaustion, then decreased from 40 to 70% of the time to exhaustion, and then markedly increased from 70% to task failure. The time course of changes in the neuromuscular parameters suggested that motor unit activation strategies changed at approximately 30 and 70% of the time to exhaustion during the sustained isometric muscle action. These findings indicate that the time course of changes in neuromuscular responses provide insight into the strategies used to delay the effects of fatigue and are valuable tools for quantifying changes in the fatiguing process during training programs or supplementation research.
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Affiliation(s)
- Cory M Smith
- 1Department of Nutrition and Health Science, University of Nebraska-Lincoln, Lincoln, Nebraska;2Department of Health, Sport, and Exercise Sciences, University of Kansas, Lawrence, Kansas;3Department of Exercise Science & Pre-Health Professions, Creighton University, Omaha, Nebraska;4Department of Exercise & Sport Science, University of Wisconsin-La Crosse, La Crosse, Wisconsin;5Department of Kinesiology & Health Promotion, University of Kentucky, Lexington, Kentucky; and6Department of Health and Human Performance, Oklahoma State University-Stillwater, Stillwater, Oklahoma
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Morel B, Hautier CA. The neuromuscular fatigue induced by repeated scrums generates instability that can be limited by appropriate recovery. Scand J Med Sci Sports 2016; 27:209-216. [PMID: 26799622 DOI: 10.1111/sms.12646] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/03/2015] [Indexed: 11/29/2022]
Abstract
The aim of this study was to evaluate the influence of the fatigue on the machine scrum pushing sagittal forces during repeated scrums and to determine the origin of the knee extensor fatigue. Twelve elite U23 rugby union front row players performed six 6-s scrums every 30 s against a dynamic scrum machine with passive or active recovery. The peak, average, and the standard deviation of the force were measured. A neuromuscular testing procedure of the knee extensors was carried out before and immediately after the repeated scrum protocol including maximal voluntary force, evoked force, and voluntary activation. The average and peak forces did not decrease after six scrums with passive recovery. The standard deviation of the force increased by 70.2 ± 42.7% (P < 0.001). Maximal voluntary/evoked force and voluntary activation decreased (respectively 25.1 ± 7.0%, 14.6 ± 5.5%, and 24 ± 9.9%; P < 0.001). The standard deviation of the force did not increase with active recovery and was associated with lower decrease of maximal voluntary/evoked force and voluntary activation (respectively 12.8 ± 7.9%, 4.9 ± 6.5%, and 7.6 ± 4.1%; all P < 0.01). As a conclusion repeated scrummaging induced an increased machine scrum pushing instability associated with central and peripheral fatigue of the knee extensors. Active recovery seems to limit all these manifestations of fatigue.
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Affiliation(s)
- B Morel
- LUNAM Université, Université du Maine, Laboratoire Motricité, Interaction, Performance EA4334, UFR Sciences et Technique, Le Mans Cedex, France
| | - C A Hautier
- Centre de Recherche et d'Innovation sur le Sport, UFRSTAPS, Université Claude Bernard Lyon 1, Villeurbanne Cedex, France
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Morel B, Rouffet DM, Saboul D, Rota S, Clémençon M, Hautier CA. Peak torque and rate of torque development influence on repeated maximal exercise performance: contractile and neural contributions. PLoS One 2015; 10:e0119719. [PMID: 25901576 PMCID: PMC4406491 DOI: 10.1371/journal.pone.0119719] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2014] [Accepted: 01/16/2015] [Indexed: 11/28/2022] Open
Abstract
Rapid force production is critical to improve performance and prevent injuries. However, changes in rate of force/torque development caused by the repetition of maximal contractions have received little attention. The aim of this study was to determine the relative influence of rate of torque development (RTD) and peak torque (Tpeak) on the overall performance (i.e. mean torque, Tmean) decrease during repeated maximal contractions and to investigate the contribution of contractile and neural mechanisms to the alteration of the various mechanical variables. Eleven well-trained men performed 20 sets of 6-s isokinetic maximal knee extensions at 240°·s-1, beginning every 30 seconds. RTD, Tpeak and Tmean as well as the Rate of EMG Rise (RER), peak EMG (EMGpeak) and mean EMG (EMGmean) of the vastus lateralis were monitored for each contraction. A wavelet transform was also performed on raw EMG signal for instant mean frequency (ifmean) calculation. A neuromuscular testing procedure was carried out before and immediately after the fatiguing protocol including evoked RTD (eRTD) and maximal evoked torque (eTpeak) induced by high frequency doublet (100 Hz). Tmean decrease was correlated to RTD and Tpeak decrease (R²=0.62; p<0.001; respectively β=0.62 and β=0.19). RER, eRTD and initial ifmean (0-225 ms) decreased after 20 sets (respectively -21.1±14.1, -25±13%, and ~20%). RTD decrease was correlated to RER decrease (R²=0.36; p<0.05). The eTpeak decreased significantly after 20 sets (24±5%; p<0.05) contrary to EMGpeak (-3.2±19.5 %; p=0.71). Our results show that reductions of RTD explained part of the alterations of the overall performance during repeated moderate velocity maximal exercise. The reductions of RTD were associated to an impairment of the ability of the central nervous system to maximally activate the muscle in the first milliseconds of the contraction.
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Affiliation(s)
- Baptiste Morel
- Center of Research and Innovation on Sport, University of Lyon 1, Villeurbanne, France
- * E-mail:
| | - David M. Rouffet
- Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia
| | - Damien Saboul
- Center of Research and Innovation on Sport, University of Lyon 1, Villeurbanne, France
- Almerys, Clermont-Ferrand, France
| | - Samuel Rota
- Center of Research and Innovation on Sport, University of Lyon 1, Villeurbanne, France
| | - Michel Clémençon
- Center of Research and Innovation on Sport, University of Lyon 1, Villeurbanne, France
| | - Christophe A. Hautier
- Center of Research and Innovation on Sport, University of Lyon 1, Villeurbanne, France
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