ELECTROMYOGRAPH ANALYSIS OF THE POPLITEUS MUSCLE IN LEVEL AND DOWNHILL WALKING

It has been proposed that the popliteus muscle is a source of lateral knee pain, typically after downhill activities. Electromyography of th e popliteus muscle was recorded in 9 normal subjects during level walk ing, downhill walking, and walking downhill wearing a 40-lb backpack ( to simulate hiking). Popliteal muscle intensity during the midstance p hase of walking downhill with weights increased significantly over tha t of level walking (30% versus 13%, respectively) (p < 0.05). There wa s a nonsignificant trend (p = 0.07) for a similar increase at terminal swing (51% versus 36%). Significantly greater knee flexion was record ed at loading response, midstance, and terminal stance (p < 0.01) duri ng both downhill trials as compared with level walking, Initial contac t position showed no differences. Velocities for downhill walking (72. 9 m/min) and downhill walking with weights (71.1 m/min) were significa ntly less than those of level walking (83.9 m/min) (p < 0.01), Stride analysis showed no significant difference in stance phase duration or in initial double-limb support times between level walking and either downhill condition. These data suggest that increased popliteal muscle activity during midstance in downhill walking with weights is in resp onse to weight bearing with an increased load on a flexed knee. Increa sed Electromyographic activity may be associated with overuse of the p opliteus muscle.