Relationship between Muscle Buffering Capacity and Fiber Type during Anaerobic Exercise in Human

Sprint-trained athletes have generally been shown to possess a higher buffering capacity than endurance-trained or sedentary subjects (Sahlin and Henriksson 1984; Parkhouse et al., 1985). Therefore, muscle with a predominance of Type II fiber is predicted to possess a greater buffer capacity than muscle with an abundance of Type I fiber. In one study, carried out on diverse groups of specifically trained athletes, significant relationships were observed between muscle buffering capacity, percentage of Type II fiber and high intensity running performance (Parkhouse et al., 1985). On the other hand, an earlier report had shown that a rather low and non-significant correlation existed between human muscle buffer values and percentage of Type II fiber at post-exercise (Essen et al., 1975). Other studies have reported no significant relationship between muscle buffering capacity and distribution of fiber type (Sahlin & Henriksson 1984; Mizuno et al., 1990; Mannion et al., 1995). There are discrepancies between the hypothesis and the human data, which may be due to differences in exercise mode or technical problems. Anaerobic ATP contribution from glycolysis during contractions performed to exhaustion with open circulation was found to be 30% higher when compared with exhausting contractions with closed circulation (Spriet, 1995). In other words, escape of lactates and associated changes in H^+ ion movement increased capacity to provide anaerobic ATP from glycolysis when circulation was open (Spriet, 1995). The objective of the present study, therefore, is to investigate whether a relationship exists between muscle buffering capacity and fiber type during ischemic exercise using a ^^31 P-NMR.