title: Neuromuscular responses to mild-muscle damaging eccentric exercise in a low glycogen state.
abstract: The aim of this study was to examine the effect of low muscle glycogen on the neuromuscular responses to maximal eccentric contractions. Fourteen healthy men (22 ± 3 years) performed single-leg cycling (20 min at ~75% maximal oxygen uptake (V̇O2 max); eight 90 s sprints at a 1:1 work-to-rest ratio (5% decrements from 90% to 55% V̇O2 max until exhaustion) the evening before 100 eccentric (1.57 rads(-1)) with reduced (RED) and normal glycogen (NORM). Neuromuscular responses were measured during and up to 48 h after with maximal voluntary and involuntary (twitch, 20 Hz and 50 Hz) isometric contractions. During eccentric contractions, peak torque decreased (RED: -16.1 ± 2.5%; NORM: -6.2 ± 5.1%) and EMG frequency increased according to muscle length. EMG activity decreased for RED only. After eccentric contractions, maximal isometric force was reduced up to 24h for NORM (-13.5 ± 5.8%) and 48 h for RED (-7.4 ± 10.9%). Twelve hours after eccentric contractions, twitch force and the 20:50 Hz ratio were decreased for RED but not for NORM. Immediate involuntary with prolonged voluntary force loss suggests that reduced glycogen is associated with increased susceptibility to mild muscle-damaging eccentric exercise with contributions of peripheral and central mechanisms to be different during recovery.
authors.affiliation: Department of Sport & Exercise Sciences, University of Chichester, Chichester, UK.
authors.forename: James P
authors.initials: JP
authors.lastname: Gavin
authors.affiliation: Department of Sport & Exercise Sciences, University of Chichester, Chichester, UK.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Myers
authors.affiliation: Department of Sport & Exercise Sciences, University of Chichester, Chichester, UK. Electronic address: m.willems@chi.ac.uk.
authors.forename: Mark E T
authors.initials: ME
authors.lastname: Willems
mesh_terms: D000328:Adult; D004576:Electromyography; D015444:Exercise; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000502:physiology*; D063806:Myalgia / Q000378:metabolism / Q000503:physiopathology*; D019415:Torque
chemical_list: D006003:Glycogen
keywords: Eccentric contractions; Muscle damage; Muscle glycogen; Neuromuscular fatigue