Alterations in the in vivo torque-velocity relationship after Achilles tendon rupture. Further evidence of speed-specific impairment.

The torque-velocity relationship of the ankle plantar flexors was determined in 31 patients recovering from Achilles tendon rupture. Isokinetic torque measurements were made at speeds of 0 to 240 degrees.s-1 at 24 degrees.s-1 intervals. Measurements of instantaneous torque were made at joint angles corresponding to neutral and 10 degrees plantar flexion. In 17 patients treated surgically, there was little difference between the injured and the uninjured leg. In contrast, patients who were treated by casting exhibited major differences between the injured and uninjured legs. This difference became amplified when torque values at 10 degrees plantar flexion were compared. Additionally, the differences between the injured and uninjured legs were not uniform. The differences in torque were greatest at slow test speeds and least at fast test speeds. Comparisons of the injured surgical and injured nonsurgical legs demonstrated that the surgical group had significantly greater torque. This difference was also speed specific. These findings demonstrate that both groups exhibited speed-specific impairment with the loss of muscle strength being greatest at slow speeds. Also, the degree of impairment was dependent on the ankle position at which torque was measured. Surgical treatment provides better functional results as observed by the torque-velocity relationship.