Method: Spinal cords of 25 rabbits were contused by 20 g⁓20 cm weight drop in the 11th thoracic spine. After 2 weeks, muscle stretch reflex was measured. Triceps surae was dissected and stretched for 5 mm at the rate of 2 mm/sec and the length-tension curve were obtained. The slope in the length-tension curve was defined as stiffness index (SI). After baseline measurement, group I (n=6) received 50 mg/kg GBP IM injection and group II (n=8) received 100 mg/kg GBP IM injection, but control group (n=5) did not. Muscle stretch reflex was measured again after 30 minutes and 60 minutes, and then after sciatic nerve section. Active tension was calculated by subtracting passive tension from total tension. Proportion of SI was calculated by dividing follow-up SI with baseline SI.

Results: The proportion of SI of active tension reduced significantly at 30 minutes and 60 minutes compared to baseline (p＜0.001, p＜0.001). The proportion of SI of active tension in both group I and group II reduced significantly than control group (p=0.041, p＜0.001). The proportion of SI of active tension in group II reduced than group I, but it was not statistically significant (p=0.166).

Conclusion: The GBP reduced significantly muscle stretch reflex in spinal cord injured rabbits and showed dose-response tendency.

Objective: To observe changes in reflex threshold and gain in spastic muscles and to find useful parameters in biomechanical assessment of spasticity.

Method: Ankle plantar flexor muscles of twenty two hemiplegic patients were stretched by isokinetic dynamometer. Stretching was done at the velocities of 10^o/sec, 300^o/sec, and at the threshold velocity (e.g. lowest velocity at which electromyographic evidence of stretch reflex was recorded). Peak eccentric torque, torque at joint angle of 20^o, torque threshold angle, and stiffness index were measured.

Results: Peak eccentric torque and stiffness index were increased and torque threshold angle was decreased in hemiplegic side. Peak eccentric torque and stiffness index were increased at 300^o/sec compared to 10^o/sec. Stiffness index showed significant correlation with modified Ashworth scale at 300^o/sec and threshold velocity.

Conclusion: Both reflex threshold and reflex gain were changed in spastic muscles. Stiffness index was thought to be one of useful parameters in biomechanical assessment of spasticity.

Objective: We designed this study to evaluate muscle tone by using a biomechanical method and to provide data for the future studies about muscle tone.

Method: We evaluated 29 subjects without known neuromuscalar diseases using the biomechanical method. Both plantar flexors of each subject were passively stretched by isokinetic dynamometer from 30^oplantar flexion position to 10^odorsiflexion position. Peak eccentric torque (PET) and torque threshold angle (TTA) were calculated at angular velocity of 10^o/sec, 90^o/sec and 300^o/sec. Regression lines from torque/position curve at 10^o/sec and 300^o/sec were considered an intrinsic stiffness index (ISI) and total stiffness index (TSI). Stretch reflex threshold speed (SRTS) was defined as the minimum speed of plantar flexion movement in which EMG reflex activity in plantar flexor muscles is induced.

Results: The mean of TTA was higher in 10^o/sec than in 300^o/sec. The means of ISI and TSI were 0.11⁑0.08, and 0.18⁑0.04. The mean of SRTS was 125.2⁑48.3^o. No statistical difference in each parameter was found according to the side or gender.

Conclusion: ISI, TSI, PET, TTA and SRTS using a biomechanical method are thought to be useful parameters for the quantitative assessment of muscle tone change of ankle plantar flexors.