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Buffer capacity of human skeletal muscle : relationships to fiber composition and anaerobic performance Parkhouse, Wade Stephen


Twenty male volunteers, comprising four distinct sub-samples (S=800m runners; R=varsity oarsmen; M=marathon runners; UT=untrained controls), participated in this study. They were made aware of the potential risks involved and informed consent was obtained. Anthropometric (hydrostatic weighing), physical characteristic and pulmonary function (Collins Respirometer) were assessed by standard techniques. Maximal oxygen consumption was determined on a progressive treadmill run (0.22 m.s⁻¹ every minute; initial speed 2.22 m.s⁻¹) to fatigue. Respiratory gases were monitered every 15 seconds (Beckman Metabolic Measurement Cart) with the four highest consecutive oxygen uptake values being averaged for determination of maximal oxygen uptake. Anaerobic performance (AST) was assessed as the time to fatigue the constant workload treadmill run at 3.52 m.s⁻¹, 20 percent incline. Post exercise blood lactate levels (HLa) were determined as an additional variable in assessment of anaerobic capacity. The M were significantly older than the other 3 groups while no significant differences existed between the trained groups for maximal oxygen uptake values. The S and R demonstrated significantly elevated AST (p<.01) and post-AST HLa (p<.05) levels above the M, whose values were similiar to the UT. This enhanced anaerobic performance could not be attributed to physical characteristic, pulmonary function or aerobic capacity differences of the trained athletes. Post-AST HLa displayed a significant relationship to anaerobic performance (r=.90). An enhanced lactate efflux mechanism was shown by the trained groups, which was not altered by training specificity. Muscle biopsies obtained at rest from the vastus lateralis muscle, were examined for fiber composition, pH, histidine and carnosine levels and buffer capacity (B). B was found to be elevated in the anaerobicly trained groups (p<.01) demonstrating a significant relationship to AST (r=.51) and fast-twitch fiber percentage (FT%; r=.51), which implied a relationship to muscle glycolytic capacity. Within the S and R, carnosine levels were found to be significantly elevated (p<.01), illustrating a significant correlation to B (r=.64) and FT% (r=.46), which emphasized the importance of carnosine as a physiological buffer and its possible relationship to the glycolytic capacity of the tissue. No differences in histidine levels or resting intramuscular pH were demonstrated with training specificity. These results suggest that the enhanced anaerobic performance could partially be attributed to elevated B and carnosine levels demonstrated within skeletal muscle subjected to anaerobic training. This may be due to the tissues enhanced capacities to seqestor the protons which accumulate during anaerobic glycolysis.

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