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Effect of Intermittent Cold Exposure on the Fiber-Type Composition of Selected Skeletal Muscles in Rats

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Final technical rept. Mar-Nov 1990

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We examined the effect of long-term intermittent cold exposure CE on the fiber-type composition of the predominantly type I soleus and the predominantly type IIb extensor digitorum longus EDL muscles of the rats. CE was accomplished by submerging the rats in shoulder-deep water, maintained at 20 0.5 deg C, for 1 hd, 5 dwk, for up to 19 weeks. Rats were randomly assigned to either a Control CON or Cold Exposure group. The efficacy of the treatment was tested by subjecting both groups to 20 deg C water for 45 minutes while measuring rectal temperature Tre and V02. The CE group displayed a 22 smaller reduction in Tre p 0.05 at the end of the exposure, and had a 23 greater V02 P 0-05 during the same period. Fiber-type composition was determined using routine histochemical methods for myosin-ATPase. The soleus muscle of the CE rats underwent a 156 increase in the number of type IIa fibers p 0.05, with a 24 reduction in type I fibers p 0.05. CE had no significant influence on the fiber-type composition of the EDL muscle. CE resulted in an increase in citrate synthase activity of 20 and 22 in the soleus and EDL muscles, respectively p 0.05. The present study demonstrates that intermittent CE induces a type I-to-type IIa transformation in the soleus muscle while having no influence on the EDL muscle.

Subject Categories:

  • Anatomy and Physiology
  • Stress Physiology

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