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Prolonged depression of knee extensor torque complexity following eccentric exercise

Pethick, Jamie, Whiteaway, Katherine, Winter, Samantha L., Burnley, Mark (2019) Prolonged depression of knee extensor torque complexity following eccentric exercise. Experimental Physiology, 104 (1). pp. 100-111. ISSN 0958-0670. (doi:10.1113/EP087295) (KAR id:70063)


Neuromuscular fatigue reduces the temporal structure, or complexity, of muscle torque output. Exercise-induced muscle damage reduces muscle torque output for considerably longer than

high-intensity fatiguing contractions. We hypothesised that muscle damaging eccentric exercise would lead to a persistent decrease in torque complexity, whereas fatiguing exercise would not. Ten healthy participants performed five isometric contractions (6 s contraction, 4 s rest) at 50% maximal voluntary contraction (MVC) before, immediately after, 10, 30 and 60 minutes, and 24 hours after eccentric (muscle damaging) and isometric (fatiguing) exercise. These contractions were also repeated 48 hours and one week after eccentric exercise. Torque and surface EMG signals were sampled throughout each test. Complexity and fractal scaling were quantified using approximate entropy (ApEn) and the detrended fluctuation analysis ? exponent (DFA ?). Global, central and peripheral perturbations were quantified using MVCs with femoral nerve stimulation. Complexity decreased following both eccentric (ApEn, mean (SD), from 0.39 (0.10) to 0.20 (0.12), P < 0.001) and isometric exercise (from 0.41 (0.13) to 0.09 (0.04); P < 0.001). After eccentric exercise ApEn and DFA ? required 24 hours to recover to baseline levels, but only 10 minutes following isometric exercise. MVC torque remained reduced (from 233.6 (74.2) to 187.5 (64.7) N.m) 48 hours after eccentric exercise, with such changes only evident up to 60 minutes following isometric exercise (MVC torque, from 246.1 (77.2) to 217.9 (71.8) N.m). The prolonged depression in maximal muscle torque output is therefore accompanied by a prolonged reduction in torque complexity.

Item Type: Article
DOI/Identification number: 10.1113/EP087295
Uncontrolled keywords: ApEn, approximate entropy; DFA detrended fluctuation analysis; MVC maximal voluntary contraction.
Subjects: G Geography. Anthropology. Recreation > GV Recreation. Leisure > Sports sciences
Divisions: Divisions > Division of Natural Sciences > Sport and Exercise Sciences
Depositing User: Mark Burnley
Date Deposited: 13 Nov 2018 13:37 UTC
Last Modified: 08 Dec 2022 23:04 UTC
Resource URI: (The current URI for this page, for reference purposes)

University of Kent Author Information

Pethick, Jamie.

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Winter, Samantha L..

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Burnley, Mark.

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