Premium
Redetermination of the optimal stimulation intensity modifies resting H‐reflex recovery after a sustained moderate‐intensity muscle contraction
Author(s) -
Rupp Thomas,
Girard Olivier,
Perrey Stéphane
Publication year - 2010
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.21512
Subject(s) - isometric exercise , stimulation , intensity (physics) , muscle contraction , contraction (grammar) , h reflex , soleus muscle , reflex , chemistry , medicine , skeletal muscle , physics , quantum mechanics
This study aimed to determine whether the time‐course of maximal resting H‐reflex amplitude (H max ) 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. H max 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 /M max ratio. During recovery, pre‐ and redetermined optimal stimulation intensities (mini‐recruitment curve drawn before each recovery measurement) were applied randomly to measure H max . 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 H max 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 H max (using mini‐recruitment curves) when the purpose is to analyze spinal modulation during the recovery phase. Muscle Nerve, 2010