Central and peripheral contributions to neuromuscular fatigue induced by a 24-h treadmill run

Abstract

This experiment investigated the fatigue induced by a 24-h running exercise (24TR) and particularly aimed at testing the hypothesis that the central component would be the main mechanism responsible for neuromuscular fatigue. Neuromuscular function evaluation was performed before, every 4 h during, and at the end of the 24TR on 12 experienced ultramarathon 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 the KE and PF, and the maximal compound muscle action potential amplitude (Mmax) on the soleus and vastus lateralis. Tetanic stimulations also were delivered to evaluate the presence of low-frequency fatigue and the KE maximal muscle force production ability. Strength loss occurred throughout the exercise, with large changes 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 reduced to a moderate extent at the end of the 24TR (-10.2%; P<0.001), but these alterations were highly variable (+/-15.7%). These results suggest that central factors are mainly responsible for the large maximal muscle torque reduction after ultraendurance 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.

Pacing Strategy During 24-Hour Ultramarathon-Distance Running

“…Considering previously published literature, we could speculate a role of fatigue in determining a reverse J-shaped pacing strategy 1,2,26 . In 24-h race simulations on a treadmill, speed declined regularly from the beginning until 16 h (similar to our study) and remained constant afterwards (different) 23,24 . Martin et al 23 showed a large maximal muscle torque reduction after the 24-h trial and an increase in ratings of perceived exertion (RPE)-from the beginning until 16 h, tending to plateau around 15 points afterwards.…”

“…In 24-h race simulations on a treadmill, speed declined regularly from the beginning until 16 h (similar to our study) and remained constant afterwards (different) 23,24 . Martin et al 23 showed a large maximal muscle torque reduction after the 24-h trial and an increase in ratings of perceived exertion (RPE)-from the beginning until 16 h, tending to plateau around 15 points afterwards. Concomitantly, Gimenez et al 24 showed an increase in oxygen uptake until 8 h, again, followed by a plateau.…”

Alteration in neuromuscular function after a 5 km running time trial

“…Large central fatigue (i.e. reduced maximal voluntary activation) was observed after running 5-24 h (Millet et al 2002a(Millet et al , b, 2011bPlace et al 2004;Martin et al 2010), while the development of peripheral fatigue is generally confined to a moderate level. In addition to a slight but significant reduction in neural drive, muscular factors are widely involved in the velocity deterioration during single (400 m, Tomazin et al 2011) or repeated (12 9 40 m, Perrey et al 2010) running sprints.…”

Prevalence and Predictors of 6-Month Fatigue in Patients With Ischemic Stroke

“…2 Poststroke fatigue is known to persist for months to years. 8,9 The time elapsed since the stroke occurred does not explain levels of fatigue. 2,10 Two years after a stroke approximately 40% of patients report that they are "always" or "often" fatigued.…”

“…7,8 Fatigue, by its very definition, involves behavioral and work performance decrement and is characterized by distress and decreased functional status related to reduced energy. 11 Poststroke fatigue often poses a barrier to return to work and reduced physical function, daily activities, quality of life, and rehabilitation potential.…”