Effects of Fatigue on the Plant Leg EMG During an Instep Soccer Kick

Abstract

Soccer competition involves powerful movements and considerable contact resulting in one of the highest incidences of injury in sports. Though many studies have focused on the relationship between fatigue and injury, there is limited research on kicking mechanics between rest and fatigue using electromyography (EMG). PURPOSE: To compare EMG average rectified values (ARV) and mean frequencies between rest and fatigue conditions for instep soccer kicking. METHODS: Fourteen male collegiate soccer players from the University of Puget Sound were asked to perform three maximal instep kicks in both rested and fatigued conditions. Criteria for acceptable kicks were determined by kicking accuracy and ball velocity. To induce the fatigued condition, subjects performed an exercise protocol established by Gleeson (1998) to simulate a soccer game. Muscle activity from the rectus femoris (RF), biceps femoris (BF), medial gastrocnemius (GM) and lateral gatrocnemius (GL) of the plant leg were collected using a portable BTS© pocket EMG before and after the exercise protocol. ARV and mean frequencies were compared between rest and fatigue conditions using dependent t-tests (p<0.05). RESULTS: The ARV of the biceps femoris decreased significantly from .262 +.113 mV at rest to .187 +.089 mV with fatigue. Although a general trend of decreasing ARV was noted from rest to fatigue in the other muscles, differences were not significant. Mean frequency was also significant from rest to fatigue in the biceps femoris, with values significantly lower at rest (86.2+20.3 Hz) than with fatigue (93.8+24.2 Hz). CONCLUSION: The fatiguing exercise protocol significantly affected the muscle activity of the biceps femoris of the plant leg during an instep soccer kick.