ArticleEffects of short duration static stretching on the denervated and reinnervated soleus muscle morphology in the rat1☆,
Section snippets
Animals and experimental protocols
Fifty-four 8-week-old female Wistar ratsa with a mean weight ± standard deviation (SD) of 185.8±9.9g were used. The following experimental protocol was approved by the ethics board of the Institute of Laboratory Animal Sciences of Kagoshima University. The rats were anesthetized by an intraperitoneal injection of sodium pentobarbital (50mg/kg). The skin covering the right buttock was cut, and the right sciatic nerve was isolated. The nerve was frozen and thawed several times by contact with a
Results
After the nerve freezing, the rats were ambulatory and dragged the foot of the frozen side. Loss of active movement in the ankle and toe joints was noted. The paralysis was alleviated, and voluntary extension of digits was noticed about 3 weeks after the operation. No apparent difference was seen in activity between groups D and S.
The distance between the proximal margin of the lesion and the entrance of the sciatic nerve into the soleus muscle was 20.1±1.7mm in group D and 20.0±1.2mm in group
Discussion
The mean fiber cross-sectional areas (fiber size) recovered 3 weeks after freezing. In this model, 70% of regenerated sciatic nerves reached the nerve terminal in the soleus muscles at 3 weeks and 100% reached that point at 4 weeks.10 It is estimated that it takes about 3 weeks for the sciatic nerve to traverse approximately 20mm to the soleus muscle, which is compatible with data reported previously.9, 10, 16
The denervation produced serious atrophy. In both the short duration static stretching
Conclusion
Denervation resulted in a reduction of fiber size and changes in fiber-type composition. The mechanical stimuli provided by short duration static stretching can delay the atrophy of type I fibers in the denervated muscle over a short period, and short-duration static stretching affect the reinnervated muscle fiber-type composition during the 4 weeks after nerve injury.
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Supported by the Ministry of Japan Culture, Education and Science (grant no. 14770738).
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