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Vie B.,Ecole de Podologie de Marseille | Brerro-Saby C.,Ecole de Podologie de Marseille | Brerro-Saby C.,Aix - Marseille University | Weber J.P.,Ecole de Podologie de Marseille | Jammes Y.,Aix - Marseille University
Gait and Posture | Year: 2013

Formulating the hypothesis that a maximal running exercise could induce fatigue of some foot muscles, we searched for electromyographic (EMG) signs of fatigue in the tibialis anterior (TA), peroneus longus (PL), and gastrocnemius medialis (GM) muscles. We also searched for post-exercise alterations of the stationary upright standing in normal-arched feet subjects. Healthy subjects performed a maximal running exercise. Surface EMGs of the TA, PL, and GM muscles were analysed during maximal dynamic efforts. Before and after the running bout, we measured the evoked compound muscle potential (M-wave) in TA, the maximal force into inversion (MIF), and the repartition of the plantar and barycentre surfaces with a computerised stationary platform.During maximal running exercise, the median frequency of the EMG spectra declined in TA while it remained stable in the PL and GM muscles. After the exercise, MIF decreased, and both the rearfoot plantar surface and the barycentre surface increased.We concluded that a maximal running bout elicits EMG signs of fatigue, though only in the TA muscle. It also elicits post-exercise changes in the foot position during stationary upright standing which indicates a foot eversion. These data solely concern a maximal running test and they can not be extrapolated to walking or running at a low speed. © 2012 Elsevier B.V.


Vie B.,Ecole de Podologie de Marseille | Gomez N.,Aix - Marseille University | Brerro-Saby C.,Ecole de Podologie de Marseille | Weber J.P.,Ecole de Podologie de Marseille | Jammes Y.,Aix - Marseille University
Journal of Biomechanics | Year: 2013

We searched for the consequences of a maximal static foot inversion sustained until exhaustion on the post-exercise stationary upright standing and the proprioceptive control of the foot muscles.Twelve healthy subjects executed an unilateral maximal static foot inversion during which continuous power spectrum analyses of surface electromyograms of the tibialis anterior (TA), peroneus longus (PL), and gastrocnemius medialis (GM) muscles were performed. Superimposed pulse trains (twitch interpolation) were delivered to the TA muscle to identify "central" or "peripheral" fatigue. Before and after the fatiguing task, we measured (1) the repartition of the plantar and barycentre surfaces with a computerized stationary platform, (2) the peak contractile TA response to electrical stimulation (TA twitch), (3) the tonic vibratory response (TVR) of TA and GM muscles, and (4) the Hoffman reflex.During static exercise, "central" fatigue was diagnosed in 5/12 subjects whereas in the 7 others "peripheral" TA fatigue was deduced from the absence of response to twitch interpolation and the post-exercise decrease in twitch amplitude. The sustained foot inversion was associated with reduced median frequency in TA but not in PL and GM muscles. After static exercise, in all subjects both the mean plantar and rearfoot surfaces increased, indicating a foot eversion, the TVR amplitude decreased in TA but did not vary in GM, and the Hoffman reflex remained unchanged.Whatever was the mechanism of fatigue during the maximal foot inversion task, the facilitating myotatic reflex was constantly altered in foot invertor muscles. This could explain the prevailing action of the antagonistic evertor muscles. © 2013 Elsevier Ltd.

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