IPC Full paper.pdf (442.43 kB)
Download file

Ischemic preconditioning blunts loss of knee extensor torque complexity with fatigue

Download (442.43 kB)
journal contribution
posted on 01.02.2021, 15:51 by Jamie Pethick, Charlotte Casselton, Sam WinterSam Winter, Mark Burnley
PETHICK, J., C. CASSELTON, S. L. WINTER, and M. BURNLEY. Ischemic Preconditioning Blunts Loss of Knee Extensor Torque Complexity with Fatigue. Med. Sci. Sports Exerc., Vol. 53, No. 2, pp. 306–315, 2021. 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.

Funding

Research project grant from the Leverhulme Trust (RPG-2016-440)

History

School

  • Sport, Exercise and Health Sciences

Published in

Medicine & Science in Sports & Exercise

Volume

53

Issue

2

Pages

306-315

Publisher

Ovid Technologies (Wolters Kluwer Health)

Version

VoR (Version of Record)

Rights holder

© The authors

Publisher statement

This is an Open Access Article. It is published by Ovid Technologies under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Acceptance date

31/07/2020

Publication date

2021-02-01

Copyright date

2021

ISSN

0195-9131

eISSN

1530-0315

Language

en

Depositor

Dr Sam Winter Deposit date: 28 January 2021