Redetermination of the optimal stimulation intensity modifies resting H-reflex recovery after a sustained moderate-intensity muscle contraction

Thomas Rupp, Olivier Girard, Stéphane Perrey

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

This study aimed to determine whether the timecourse of maximal resting H-reflex amplitude (Hmax) recovery after a prolonged moderate-intensity muscle contraction differs according to the optimal stimulation intensity used (predetermined vs. readjusted). Thirteen males performed a sustained isometric plantar flexion at 40% of their maximal voluntary contraction torque output until exhaustion. Hmax of the soleus muscle was recorded before and 2, 6, 10, and 14 min after the end of the contraction, then normalized by the respective maximal M-wave to form the H max/Mmax ratio. During recovery, pre- and redetermined optimal stimulation intensities (mini-recruitment curve drawn before each recovery measurement) were applied randomly to measure Hmax. When using redetermined stimulation intensities, normalized H-reflex values were systematically greater (+11, +16, +15, and +15% after 2-, 6-, 10-, and 14-min recovery periods, respectively) than those obtained with the predetermined intensity. Keeping the stimulation intensity constant to evoke Hmax after a sustained muscle contraction can underestimate the H-reflex facilitation occurring after exhaustive exercise. It is therefore more appropriate to redefine the optimal stimulation intensity to evoke Hmax (using mini-recruitment curves) when the purpose is to analyze spinal modulation during the recovery phase.

Original languageEnglish
Pages (from-to)642-650
Number of pages9
JournalMuscle and Nerve
Volume41
Issue number5
DOIs
Publication statusPublished - 1 May 2010
Externally publishedYes

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