EFFECTS OF CREATINE LOADING AND TRAINING ON RUNNING PERFORMANCE AND BIOCHEMICAL-PROPERTIES OF RAT SKELETAL-MUSCLE

Several reports have shown that the use of oral creatine (Cr) suppleme ntation can increase performance during brief high intensity exercise in humans. The purpose of this study was to examine the separate and c ombined effects of Cr supplementation and high intensity run training on the performance capacity and biochemical properties of rodent skele tal muscle. Running performance was assessed following acute (10-d) an d chronic (4-wk) Cr supplementation. Results indicate that Cr suppleme ntation alone has ergogenic effects and the combination of run trainin g plus Cr results in a more pronounced enhancement of performance than either intervention alone. The benefits of Cr supplementation were se en most clearly during repetitive bouts of high intensity interval run ning. Cr concentrations increased in both the slow soleus and fast pla ntaris muscles (P < 0.05) in response to Cr supplementation. Increased creatine concentrations appeared to be reflected in increased phospho rylated creatine (PCr). Citrate synthase (CS) activity was increased i n both the soleus and plantaris muscles following training (P < 0.05). CS activity of the untrained soleus but not the plantaris responded t o the dietary stimulus. There were no significant changes in either cr eatine phosphokinase activity or myosin heavy chain isoform distributi on following training or supplementation. These results indicate that the gains in high intensity running performance seen following Cr load ing are a combined result of increased aerobic (CS) and anaerobic (Cr and PCr) energy buffering capacity of the muscle.