THE EFFECTS OF CREATINE SUPPLEMENTATION ON MUSCLE ENERGY METABOLISM DURING SUBMAXIMAL EXERCISE WITH ARTERIAL OCCLUSION

Abstract

PURPOSE The purpose of this study was to evaluate the rate of ATP synthesis through phosphocreatine (PCr) hydrolysis, glycolysis, and exercise performance during ischemic submaximal dynamic handgrip exercise before and after creatine (Cr) supplementation. METHODS Forearm muscles of eleven healthy male subjects [age = 21.9 ± 1.1 yr (Mean ± SE)] were examined during submaximal dynamic handgrip exercise with arterial occlusion (Ex-Oc) using 31P-MRS before and after ingestion with 30 g Cr monohydrate or placebo per day for 14 days. RESULTS Before treatment, the ATP synthesis percentage through glycolysis during EX-Oc was 73.2 ± 2.6% in all eleven subjects. Cr supplementation produced a 15.5 ± 3.0% increase in the resting muscle PCr concentration. The rate of ATP synthesis through PCr hydrolysis during Ex-Oc increased from 0.14 ± 0.02 (pre-value) to 0.19 ± 0.01 mmol/kg ww/sec (post-value, P <0.05). Cr supplementation produced a 8.9 ± 2.4% increase in time to exhaustion during Ex-Oc. An increase in PCr degradation during Ex-Oc after Cr supplementation positively correlated with the increase in time to exhaustion (r = 0.93, p <0.05). CONCLUSION The results indicate that an improvement in performance during Ex-Oc after Cr supplementation was associated with the increased PCr availability for the synthesis of ATP, although the major pathway of ATP synthesis during EX-Oc was through glycolysis.