Effect of quadriceps femoris muscle stretch on knee extension torque

Peak and angle specific knee extension torques produced after a quadriceps femoris muscle stretch and after a 15-second rest were compared to determine the effect of stretch on knee extension torque. Twenty healthy subjects performed eight maximum voluntary knee extensions at 90 degrees/sec under each condition. Although peak torque and torques at 15, 30, 45, and 60 degrees from full extension were measured, knee extension torque was only significantly greater (p less than .02) at 60 degrees of knee flexion after quadriceps femoris muscle stretch. The absolute difference, which was only a mean 4.9 N X m (3.6 ft-lb), was not substantial. When quadriceps femoris muscle stretch is a consequence of passive knee flexion at 90 degrees/sec, knee extension torque is apparently facilitated only during the initial part of the knee extension movement. Therefore, in healthy patients, a muscle stretch, such as used in this study, is probably of little therapeutic value.