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Ischemic Preconditioning Blunts Loss of Knee Extensor Torque Complexity with Fatigue.

Pethick, Jamie and Casselton, Charlotte and Winter, Samantha L and Burnley, Mark (2021) 'Ischemic Preconditioning Blunts Loss of Knee Extensor Torque Complexity with Fatigue.' Medicine and Science in Sports and Exercise, 53 (2). pp. 306-315. ISSN 0195-9131

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Introduction Neuromuscular fatigue reduces the temporal structure, or complexity, of muscle torque output, purportedly through an effect on motor unit behavior. Ischemic preconditioning (IPC), an emerging ergogenic aid, has been demonstrated to have a potent effect on muscular output and endurance. We therefore tested the hypothesis that IPC would attenuate the fatigue-induced loss of muscle torque complexity. Methods Ten healthy participants (6 males/4 females) performed intermittent isometric knee extension contractions (6 s contraction, 4 s rest) to task failure at 40% maximal voluntary contraction. Contractions were preceded by either IPC (three bouts of 5 min proximal thigh occlusion at 225 mm Hg, interspersed with 5 min rest) or SHAM (as IPC, but occlusion at only 20 mm Hg) treatments. Torque and EMG signals were sampled continuously. Complexity and fractal scaling were quantified using approximate entropy (ApEn) and the detrended fluctuation analysis (DFA) α scaling exponent. Muscle oxygen consumption (mV˙O2) was determined using near-infrared spectroscopy. Results IPC increased time to task failure by 43% ± 13% (mean ± SEM, P = 0.047). Complexity decreased in both trials (decreased ApEn, increased DFA α; both P < 0.001), although the rate of decrease was significantly lower after IPC (ApEn, −0.2 ± 0.1 vs –0.4 ± 0.1, P = 0.013; DFA α, 0.2 ± 0.1 vs 0.3 ± 0.1, P = 0.037). Similarly, the rates of increase in EMG amplitude (P = 0.022) and mV˙O2 (P = 0.043) were significantly slower after IPC. Conclusion These results suggest that the ergogenic effect of IPC observed here is of neural origin and accounts for the slowing of the rates of change in torque complexity, EMG amplitude, and mV˙O2 as fatigue develops.

Item Type: Article
Uncontrolled Keywords: Knee; Thigh; Muscle, Skeletal; Femoral Nerve; Humans; Spectroscopy, Near-Infrared; Electromyography; Exercise; Electric Stimulation; Task Performance and Analysis; Muscle Fatigue; Isometric Contraction; Torque; Adult; Female; Male; Young Adult
Divisions: Faculty of Science and Health
Faculty of Science and Health > Sport, Rehabilitation and Exercise Sciences, School of
SWORD Depositor: Elements
Depositing User: Elements
Date Deposited: 21 Feb 2022 19:32
Last Modified: 21 Feb 2022 19:32

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