This study investigated the neuromuscular fatigue following an elastic band exercise (EB) of the plantar flexors, compared to an intermittent phasic isometric exercise (ISO). Eleven young healthy males (age: 24.2 ± 3.7) took part in the study, consisting of one experimental session involving two 5-min fatiguing protocols separated by 20 min rest and performed randomly. Both exercises were performed at maximal motor output of the plantar flexor muscles, EMG being used as a feedback signal. Neuromuscular fatigue was assessed through changes in maximal voluntary contraction (MVC) and in evoked responses of soleus and gastrocnemii muscles to posterior tibial nerve stimulation (H-reflex, M-wave, V-wave). Both conditions induced significant decrease in MVC force, but to a greater extent after EB (-20.0 ± 5.1%, P < 0.001) than after ISO (-12.3 ± 4.6%, P = 0.037). While no effect was observed in M-wave amplitude after both exercises, EB resulted in greater decrease of normalized H-reflexes compared to isometric condition. Normalized V-wave significantly decreased only after EB. As a conclusion, the greater fatigability found after EB as compared to ISO was underlain by muscular as well as nervous factors. This higher impact was attributed to the dynamic nature of elastic band exercise as compared to isometric contractions.
Keywords: Electromyography; Force; H-reflex; M-wave; Triceps surae; V-wave.
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