ANAEROBIC ENERGY-PRODUCTION IN HUMAN SKELETAL-MUSCLE IN INTENSE CONTRACTION - A COMPARISON OF P-31 MAGNETIC-RESONANCE SPECTROSCOPY AND BIOCHEMICAL TECHNIQUES

Five subjects underwent twenty electrically evoked maximal isometric c ontractions of the anterior tibialis muscle of both legs (n = 10), wit h limb blood flow occluded. Measurements of muscle high-energy phospha tes (ATP, ADP and phosphocreatine (PCr)), lactate and pH were made usi ng both P-31 magnetic resonance spectroscopy (MRS) and the biochemical analysis of biopsy samples obtained from directly below the MRS surfa ce coil. The resting PCr concentration determined using MRS was simila r to that measured in the biopsy material. Following contraction, MRS showed a greater decrease in ATP concentration compared with biochemic al analysis (P < 0.05), but the decrease in PCr was similar. Good agre ement was found when comparing resting muscle pH estimated by The two methods. Post-exercise muscle pH was, however, consistently lower with MRS and consequently the accumulation of muscle lactate estimated usi ng MRS was markedly greater than the corresponding biochemical measure ment (P < 0.05). As a result, MRS revealed an similar to 30% greater a naerobic ATP turnover during contraction, although this just failed to reach statistical significance (P > 0.05). The results of the present study indicate that there is little difference in the muscle concentr ation of PCr estimated by the two methods, but that there are differen ces in the estimates of ATP, pH and lactate changes during contraction . This latter discrepancy may lead to greater estimates of ATP turnove r being made as a result of MRS analysis.