Leg muscle activation patterns of sit-to-stand movement in stroke patients.

OBJECTIVE: To describe the characteristics of leg muscle activation patterns in hemiplegic stroke patients during the movement of rising from a chair and to determine the differences of leg muscle activation patterns between stroke fallers and nonfallers.
DESIGN: Subjects stood up from an armless chair at a comfortable, self-paced speed. Leg muscle activation time and patterns during the sit-to-stand movement were analyzed using multichannel surface electromyography and a force platform. The differences between stroke fallers and nonfallers were compared.
RESULTS: The mean onset time of muscle activity in the affected limbs of stroke fallers was markedly delayed for the tibialis anterior muscle and earlier for the soleus muscle. The muscle activation patterns in the affected side of the stroke fallers exhibited a wide range of variation. Seventy percent of our stroke fallers exhibited no or merely low-amplitude activity in their tibialis anterior muscle when the patients were rising from a chair. Half of the stroke fallers exhibited premature or excessive activation of their soleus muscle when the rising activity was initiated.
CONCLUSIONS: Stroke patients who exhibited no or low-amplitude muscle activity in the tibialis anterior, associated with premature or excessive activation of the soleus muscle in their hemiplegic limbs, when rising from a chair were prone to falling. The compensatory excessive tibialis anterior and quadriceps muscle activation in the unaffected limbs of stroke patients might have a role in preventing them from falling.