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 (βmin vivo and βmin vitro) and RSA. Thirty-four untrained females [mean (SD): age 19 (1) years, maximum oxygen uptake (V̇O2peak) 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 (pHb) 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) pHi, βmin vivo and βmin vitro. There were significant correlations between work decrement (%) and βmin vivo (r=−0.72, P<0.05), V̇O2peak (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 βmin 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 βmin vitro, βmin vivo, or changes in [La−]i, pHi, [La−]b, or pHb. There were significant correlations between total work (J·kg−1) and both V̇O2peak (r=0.60, P<0.05) and LT(r=0.54, P