Objective
To determine the differences of the tendon reflex responses (TRR) between medial and lateral heads of gastrocnemius muscles in healthy subject and spastic patients.

Method
The TRR of medial and lateral heads were evaluated in 20 healthy subjects and 20 spastic hemiplegic patients. From 5 repeated trials on each subject, the shortest latency and duration, and the largest peak-to-peak amplitude of TRR were chosen for the representative value.

Results
1. The evoked potentials by tendon reflex in medial head of gastrocnemius demonstrated significantly higher amplitude than in the lateral head of gastrocnemius in patients (P＜0.05) and the evoked potentials in lateral head of gastrocnemius demonstrated significantly higher amplitude than in the medial head of gastrocnemius in healthy patients (P＜0.05). 2. Mean latency of the evoked potentials by a tendon reflex in both heads of gastrocnemius in the spastic patients and healthy subjects were not significantly different (P＞0.05). 3. Mean duration of the evoked potentials by a tendon reflex in both heads of gastrocnemius in spastic patients and healthy subjects were not significantly different (P＞0.05).

Conclusion
These results indicate that the medial head of gastrocnemius is activated more than the lateral head of gastrocnemius by a tendon reflex in recording evoked potentials of the spastic patients.