The effects of pain induced by blood flow occlusion in one leg on exercise tolerance and corticospinal excitability and inhibition of the contralateral leg in males.

Abstract

Experiencing pain in one leg can alter exercise tolerance and neuromuscular fatigue (NMF) responses in the contralateral leg; however, the corticospinal modulations to nonlocal experimental pain induced by blood flow occlusion remain unknown. In three randomized visits, 13 male participants performed 25% of isometric maximal voluntary contraction (25%IMVC) to task failure with one leg preceded by (i) 6-min rest (CON), (ii) cycling at 80% of peak power output until task failure with the contralateral leg (CYCL), or (iii) CYCL followed by blood flow occlusion (OCCL) during 25%IMVC. NMF assessments (IMVC, voluntary activation [VA], and potentiated twitch [Qtw]) were performed at baseline and task failure. During the 25%IMVC, transcranial magnetic stimulations were performed to obtain motor-evoked potential (MEP), silent period (SP), and short intracortical inhibition (SICI). 25%IMVC was the shortest in OCCL (105±50s)and shorter in CYCL (154±68s)than CON (219±105s)(p<0.05). IMVC declined less after OCCL (-24±19%) and CYCL (-27±18%), then CON (-35±11%) (p<0.05). Qtw declined less in OCCL (-40±25%) compared to CYCL (-50±22%) and CON (-50±21%) (p<0.05). VA was similar amongst conditions. MEP and SP increased and SICI decreased throughout the task, while SP was longer for OCCL compared to CYC condition (p<0.05). The results suggest that pain in one leg diminishes contralateral limb exercise tolerance and NMF development and modulate corticospinal inhibition in males. Novelty: Pain in one leg diminished MVC and twitch force decline in the contralateral limb. Experimental pain induced by blood flow occlusion may modulation corticospinal inhibition of the neural circuitries innervating the contralateral exercise limb.