Response of hamstring muscles to a perturbation in people with chronic anterior cruciate ligament deficiency

A number of strength parameters were investigated in a group of subjects with chronic anterior cruciate ligament deficiency; The response of subjects' hamstring muscles to a perturbation on an isokinetic dynamometer was fractionated into the premotor and motor times. Rate of force development in the 75 ms following the perturbation was also measured. The functional ability of the subjects was examined using the Noyes knee rating system. The results showed that the motor time was significantly correlated with the rate of force development and functional ability of the subjects. The ratio of hamstring to quadriceps torque recorded at peak and 30° flexion during isokinetic muscle work at 180°/s was also investigated. No significant relationship was observed between these ratios and functional ability. These findings indicate that factors other than peak hamstring muscle torque may be important to the level of functional ability attained by people with chronic anterior cruciate ligament deficiency.