| CENTRAL AND PERIPHERAL CONTRIBUTIONS TO NEUROMUSCULAR 3 FATIGUE INDUCED BY A 24-HOUR TREADMILL RUN |
 |
 |
|
No hay traducciones disponibles.
ABSTRACT
This experiment investigated the fatigue induced by a 24-hour running exercise (24TR) and particularly aimed at testing the hypothesis that the central component would be themain mechanism responsible for neuromuscular fatigue. Neuromuscular function evaluation was performed before, every 4 hours during and at the end of the 24TR on 12 experienced ultra-marathon runners. It consisted of a determination of the maximal voluntary contractions(MVC) of the knee extensors (KE) and plantar flexors (PF), the maximal voluntary activation (%VA) of KE and PF, the maximal compound muscle action potential amplitude (Mmax) on soleus and vastus lateralis. Tetanic stimulations were also delivered to evaluate the presence of low frequency fatigue, and the KE maximal muscle force production ability. Strength loss occurred throughout the exercise, large changes being observed after 24TR in MVC for both the KE and PF muscles (-40.9 ± 17.0% and - 30.3 ± 12.5%, respectively; P < 0.001) together with marked reductions of %VA (-33.0 ± 21.8% and -14.8 ± 18.9%, respectively; P < 0.001). A reduction of Mmax amplitude was observed only on soleus and no low frequency fatigue was observed for any muscle group. Finally, KE maximal force production ability was 43 reduced to a moderate extent at the end of the 24TR (-10.2%; P < 0.001) but these alterations 44 were highly variable (± 15.7%). These results suggest that central factors are mainly responsible for the large maximal muscle torque reduction after ultra-endurance running, especially on the KE muscles. Neural drive reduction may have contributed to the relative
preservation of peripheral function and also affected the evolution of the running speed during the 24TR.
|
