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RESEARCH PRODUCT

Altérations neuromusculaires induites par des exercices excentriques et concentriques fatigants : emphase sur le pédalage des membres inférieurs

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description

The influence of dynamic contraction type (concentric or eccentric) on performance fatigability and associated neuromuscular alterations is partly unknown. Contraction type interacts with other exercise features such as intensity (maximal; submaximal) or modality (single-joint; locomotor). Thus, we compared eccentric with concentric exercises of similar characteristics across three experimental studies. We showed that, for the completion of a given amount of mechanical work, both contraction types impaired maximal voluntary isometric torque similarly. However, neuromuscular impairments depended on exercise features. In study 1, maximal single-joint eccentric contractions affected neural but not contractile function, and concentric exercises exhibited the opposite effect. In study 2, eccentric and concentric cycling at the same power output caused similar neuromuscular alterations, apart from an impairment of the excitation-contraction coupling process after eccentric cycling only. Along with the literature, these two studies suggest that contraction type only affects post-exercise neuromuscular perturbations when exercise intensity is maximal. Study 3 showed no change in the neural control of pedaling during fatiguing concentric or eccentric cycling at the same power output. Yet we found a greater excitability and relative inhibition of the corticospinal pathway to the knee extensor muscles, during concentric compared with eccentric cycling, respectively. Overall, these results provide specifications on the effects of eccentric contractions on neuromuscular function et offer research perspectives. Notably, the processes underpinning the relative corticospinal inhibition during eccentric cycling may be investigated by applying transcranial and pyramidal tract stimulations during the silent period.