Muscle buffer capacity and aerobic fitness are associated with repeated-sprint ability in women

In addition to a high aerobic fitness, the ability to buffer hydrogen ions (H+) may also be important for repeated-sprint ability (RSA). We therefore investigated the relationship between muscle buffer capacity (betam(in vivo) and betam(in vitro)) and RSA. Thirty-four untrained females [mean (SD): age 19 (1) years, maximum oxygen uptake ((V) over dot O-2peak) 42.3 (7.1) ml.kg(-1).min(-1)] completed a graded exercise test (GXT), followed by a RSA cycle test (five 6-s sprints, every 30 s). Capillary blood was sampled during the GXT and before and after the RSA test to determine blood pH (pH(b)) and lactate concentration ([La-](b)). Muscle biopsies were taken before (n=34) and after (n=23) the RSA test to determine muscle lactate concentration ([La-](i)), hydrogen ion concentration ([H+](i)) pH(i), betam(in vivo) and betam(in vitro). There were significant correlations between work decrement (%) and betam(in vivo) (r=-0.72, P<0.05), (V) over dot O-2peak (r=-0.62, P<0.05), lactate threshold (LT) (r=-0.56, P<0.05) and changes in [H+](i) (r=0.41, P<0.05). There were however, no significant correlations between work decrement and betam(in vitro), or changes in [La-](i), or [La-](b). There were also no significant correlations between total work (J.kg(-1)) during the RSA test and betam(in vitro), betam(in vivo), or changes in [La-](i), pH(i), [La-](b), or pH(b). There were significant correlations between total work (J.kg(-1)) and both (V) over dot O-2peak (r=0.60, P<0.05) and LT(r=0.54, P<0.05). These results support previous research, identifying a relationship between RSA and aerobic fitness. This study is the first to identify a relationship between betam(in vivo) and RSA. This suggests that the ability to buffer H+ may be important for maintaining performance during brief, repeated sprints.