Abstract
Thirty (n=30) seven week old male Sprague-Dawley rats were divided into six groups of five rats (n=5) in each group. The groups were designated Sc=sea level controls; St=sea level trained; Fc=hypoxic exposed (16% O2) controls; Ft =hypoxic exposed (16% O2) trained; Pc=intermittent hypoxic exposed (18%, 16%, 14%, 16%, 18% O2 for two days each) controls; and Pt=intermittent hypoxic exercise trained. Exercise training consisted of 45min/day running on a rat treadwheel for 24 consecutive days. Fiber type distribution, succinate dehydrogenase (SDH) activity and glycogen content of the soleus muscle and the oxidative enzyme activity of the motoneurons of the soleus were measured in each group after the 24 days of hypoxic exposure and exercise training. In comparison to each training group's control the glycogen concentration of the soleus muscle was increased (P<0.05) regardless of hypoxic exposure. Only the intermittently hypoxic exercise trained group (Pt) demonstrated a fiber type shift of slow-twitch oxidative to fast-twitch oxidative glycolytic fibers. Neither hypoxia or exercise training altered the oxidative enzyme capacity of the soleus motoneurons.
