Method
Sciatic nerve of seventy rats was compressed with haemostatic forceps. The experimental group was divided into 4 subgroups according to the intensity and duration of injury: group 1, first degree compression for 5 seconds; group 2, first degree for 30 seconds; group 3, third degree for 5 seconds; and group 4, third degree for 30 seconds. Treadmill exercise was done for either 30 minutes or 2 hours a day, 5 days a week for 4 weeks. Histochemical study of soleus was done before nerve compression and 1 week, 4 weeks after compression.

Results
The fiber diameter of soleus was larger in the experimental group at 4 weeks (p＜0.05). The intensity of injury had greater impact on the recovery of fiber diameter than the duration. Thirty minute exercise was seen to have a earlier recovery of fiber diameter than 2 hours.

Conclusion
These results may provide the basic data to clarify the neurological recovery in relation to the severity of injury, and to help establishing adequate duration of exercise after nerve damage.