Relationship between torque and EMG activity of a knee extensor muscle during isokinetic concentric and eccentric actions.

Integrated surface electromyographic (IEMG) activity of the vastus lateralis portion of the quadriceps muscle and knee torque were recorded during isokinetic concentric and eccentric actions, performed at maximum effort at a fixed velocity of 30 degrees s(-1) through 80-20 degrees knee flexion in 15 trained athletes. Mean IEMG and torque data were calculated for three ranges, viz. outer (25-44 degrees ), mid (45-54 degrees ) and inner (55-74 degrees ) and normalized as a percentage of mid-range concentric values. No significant difference was seen in IEMG activity either between left and right muscle or between concentric and eccentric action at any joint angle range. Similarly no significant difference was seen in torque between left and right muscle at any joint angle range. However, there was a significant difference in knee torque between the three angular ranges and between concentric and eccentric actions. It is concluded that no fixed relationship exists between vastus lateralis IEMG and quadriceps torque during maximum concentric and eccentric actions.