Co-activation Index of Muscles Across Knee and Ankle during Sit to Stand in Normal Young Individuals: A Pilot Study

Loss of selective motor output is a major component for impaired mobility, which has been attributed to increased co-activation among individuals with supraspinal lesions. Increased coactivation of antagonist muscle contributes to the pathomechanics in the joint by weakening the agonist muscle function. Transitional movements like sit to stand is a prerequisite for many functional activity of daily living. Our main aim is to study and quantify co-activation across knee and ankle during sit to stand which can be used as an outcome for therapeutic purposes.

Six healthy young adults (age: 22.6 ± 2.4yrs) participated in the study. Participants performed Sit to stand movement. Muscle activity from quadriceps, hamstring, tibialis anterior and gastrocnemius were recorded by using EMG and simultaneous video was recorded to analyse the quality of movement. The best three trials were taken to calculate co-activation index across knee and ankle.

Co-activation index across knee was found to be 58.07±21.81% and that of ankle was 29.24±2.85%. Constant firing was observed in tibialis anterior throughout the movement. Maximum activity was seen in quadriceps during the descent phase of sit to stand.