GLYCOGEN DEPLETION AND RESYNTHESIS IN THE RAT AFTER DOWNHILL RUNNING

To study the effect of downhill running on glycogen metabolism, 94 rats were exercised by running for 3 h on the level or down an 18-degrees incline. Muscle and liver glycogen concentrations were measured before exercise and 0, 48 and 52 h postexercise. Rats were not fed during the first 48 h of recovery but ingested a glucose solution 48 h postexercise. Downhill running depleted glycogen in the soleus muscle and liver significantly more than level running (P < 0.01). The amount of glycogen resynthesized in the soleus muscle and liver in fasting or nonfasting rats was not altered significantly by downhill running (P > 0.05). On every day of recovery the rats were injected with dexamethasone, which induced similar increases in glycogen concentration in the soleus muscle and liver after the 52nd h of the postexercise period in the case of downhill and level running. The glycogen depletion and repletion results indicated that, under our experimental conditions, downhill running in the rat, a known model of eccentric exercise, affected muscle glycogen metabolism differently from eccentric cycling in humans.