Abstract
Our study focuses on the effect of ankle plantar flexors fatigue on force production and running parameters.
Muscle fatigue is defined as a reduction of maximal strength or power of the muscle. It develops gradually soon after the onset of sustained activity and does not correspond to the moment when it is unable to maintain a task.
We used two different fatigue protocols of the ankle flexor muscles:
1) Theisokineticapparatus(thegoldstandard),adevicewhichisbulky,expensive and time consuming for tests. The isokinetic fatigue protocol induces fatigue by performing maximal isokinetic contractions.
2) The single-leg Heel-Raise, which is a simple, cheap and fast for testing. The Heel-Raise fatigue protocol is a combination of concentric and eccentric loading of the plantar flexor muscle. When a subject is performing a Heel-Raise protocol, he moves his body mass against gravity.
Then we assessed the effects of the two fatigue protocols with two different methods:
1) Analytic clinical way: effects of fatigue on force. We used a hand-held dynamometer (HHD), for the recording of the strength of maximal voluntary contractions (MVC).
2) Functional way (Running): effects of fatigue on running parameters. We used a treadmill for the recording of qualitative parameters (running economy).
The aim of our study was to compare the effect of functional Heel-Raise induced fatigue versus isokinetic induced fatigue protocols on MVC and on running economy.
For the time being, available clinical evaluations are only done in static or running mode, but without pre-fatigue considerations.
In total, 18 subjects participated in the study. The study was conducted over two days of testing at the Hôpital de la Tour in Meyrin (GE). The participants considered for the study practice physical activities from moderate to vigorous level, are healthy and without known cardiovascular or metabolic comorbidities.
Regarding the effects of the two fatigue protocols on force production and running economy, we noticed that our fatigue protocols do not fatigue as much as initially thought. Nevertheless, we observed a few pre and post test differences on strength and running economy. Differences were mainly observed between men and women.