Phosphocreatine Resynthesis During Recovery After Exercise With Blood Flow Occlusion.

Abstract

Previous studies (e.g., Biochem. J. 291: 681, 1992; Magn. Reson. Med. 49:623, 2003) suggest that glycogenolysis in skeletal muscle is tightly coupled to contraction, such that phosphocreatine (PCr) resynthesis after exercise is entirely dependent on oxidative metabolism. In contrast, an initial phase of PCr recovery which is faster than can be accounted for by oxidative metabolism was observed after intense exercise in rat muscle (Proc. ISMRM 5: 1309, 1997), and more recently in human muscle (companion abstract). PURPOSE: to examine PCr recovery in human muscle during partial and complete occlusion of blood flow. METHODS: PCr was measured by 31P-NMR (3T, TR 3 s) in anterior tibial muscle of 8 healthy subjects (range 20-55 yrs old, 3 female) after 1 minute of repetitive ankle dorsiflexion exercise under 3 conditions: no occlusion, partial occlusion (120 Torr cuff above knee), and complete occlusion (180 Torr cuff). In 4 subjects, blood flow in the anterior tibial artery was measured after exercise under the same conditions by CINE-PC MR angiography. RESULTS: With no occlusion both PCr (Figure, left) and blood flow (right) recovered near exponentially. During partial occlusion PCr recovery showed an initial, fast phase, followed by a slow, linear phase, suggesting that recovery rate was limited by the low flow observed under this condition. During complete occlusion, this slow linear recovery phase was abolished, but a brief, initial phase of PCr recovery remained.FigureCONCLUSION: The results suggest that the initial, fast phase of PCr recovery observed after intense, repetitive exercise is driven in part by anaerobic glycogenolysis, and hence, that PCr recovery is not entirely dependent on oxidative metabolism. (Supported by NIH AR043903)