Effect of ankle position on EMG activity and peak torque of the knee extensors and flexors during isokinetic testing

The purpose of this study was to examine the effect of ankle position on the electromyographic (EMG) activity, peak torque, and peak knee flexion to extension torque ratio during isokinetic testing of the knee. Twelve healthy female athletes performed six maximal knee extension and flexion repetitions with their dominant legs at 60 and 180 degrees/s with the ankle in a plantar flexed position and again in a dorsiflexed position. Root mean square EMG (rmsEMG) activity was determined by placing bipolar surface electrodes on the quadriceps and the hamstrings. Ankle position had no effect on the rmsEMG activity of the quadriceps or the hamstrings at either 60 or 180 degrees/s. Significant differences were noted for peak flexor torque at 60 degrees/s (p < .001) and 180 degrees/s (p < .01) and for peak torque flexor/extensor ratio (p < .01), with higher values observed with ankle dorsiflexion. This suggests that ankle position affects knee flexor torque and flexor/extensor ratio but not hamstring activity during isokinetic testing of the knee.