Effects of the exercise-induced muscular fatigue on the time of muscular reaction of the fibularis in healthy individuals

The muscular fatigue (MF) is a common phenomenon in the daily sports activities that results in a worsening of the motor performance. It is considered one of the major factors for muscleskeletal damages, such as the ankle sprain, when the MF would affect both the afferent and the efferent systems. Several studies have been analyzing the influence of the MF on the neuromuscular control (NMC). Nevertheless, there are few researches comprising that influence on the velocity of the muscular reaction. The purpose of this study was to check the effects of the MF on the time of the muscular reaction (TMR) in the fibularis muscles, which are the first to respond to an inversion stress of the ankle. Fourteen healthy male individuals (age: 20-35 years) were studied, who had their TMR assessed by means of the surface electromyography (EMG). The beginning of the muscular activity was defined as the mean resting value +3x the standard deviation (SD). The TMR of the fibularis was measured after a sudden 20o inversion performed on a platform. The sudden inversion was performed before and after the muscular fatigue, which was induced through localized exercises of the fibularis up to the exhaustion. The results have shown a significant increase in the time of the muscular reaction after the fatigue (p < 0.01). While performing prolonged sportive activities and during the rehabilitation process, there must be caution to perform tasks that require extremely fast muscular responses.