Journal
JOURNAL OF APPLIED PHYSIOLOGY
Volume 94, Issue 1, Pages 193-198Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/japplphysiol.00600.2002
Keywords
low- and high-frequency electrical stimulation; central activation; M wave; electromyogram
Categories
Ask authors/readers for more resources
The aim of this study was to identify the mechanisms that contribute to the decline in knee extensor (KE) muscles strength after a prolonged running exercise. During the 2 days preceding a 30-km running race [duration 188.7+/-27.0 (SD) min] and immediately after the race, maximal percutaneous electrical stimulations (single twitch, 0.5-s tetanus at 20 and 80 Hz) were applied to the femoral nerve of 12 trained runners. Superimposed twitches were also delivered during isometric maximal voluntary contraction (MVC) to determine the level of voluntary activation (%VA). The vastus lateralis electromyogram. was recorded. KE MVC decreased from pre- to postexercise (from 188.1+/-25.2 to 142.7+/-29.7 N-m; P<0.001) as did %VA (fro 98.8 +/- 1.8 to 91.3 +/- 10.7%; P<0.05). The changes from pre- to postexercise in these two variables were highly correlated (R=0.88; P<0.001). The modifications in the mechanical response after the 80-Hz stimulation and M-wave peak-to-peak amplitude were also significant (P<0.001 and P<0.05, respectively). It can be concluded that 1) central fatigue, neuromuscular propagation, and muscular factors are involved in the 23.5 +/- 14.9% reduction in MVC after a prolonged running bout at racing pace and 2) runners with the greatest KE strength loss experience large activation deficit.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available