MUSCLE ACTIVATION PATTERNS AT THE KNEE JOINT DURING UNANTICIPATED SIDESTEPPING TASKS

Abstract

The purpose of this paper was to investigate the muscle activation patterns during preplanned (PP) and unanticipated (UN) sidestepping tasks, with respect to the external moments applied to the joint. Ten healthy male subjects performed running and sidestepping tasks under PP and UN conditions. Activation from ten knee muscles was estimated using surface EMG and averaged across stages of the stance phase. Selective activation of medial and lateral muscles and co-contraction of flexors and extensors were used to stabilise the joint under PP conditions, whereas only generalised co-contraction strategies were employed during the UN condition. Net muscle activation during the UN sidestepping tasks only increased by 10-20%, compared with the 200% increase in external joint load. This study has implications for the prevention of ligament injuries.