The effects of training intensity on muscle buffer capacity in females

We examined changes in muscle buffer capacity (βmin vitro), and the lactate threshold (LT) after 5 weeks of high-intensity interval training (INT) above the LT or moderate-intensity continuous training (CON) just below the LT. Prior to and immediately after training, 16 female subjects performed a graded exercise test to determine and the LT, followed 2 days later by a resting muscle biopsy from the vastus lateralis muscle to determine βmin vitro. Following baseline testing, the subjects were randomly placed into the INT (n=8) or CON training group (n=8). Subjects then performed 5 weeks of cycle training (3 days per week), performing either high-intensity INT (6–10×2 min at 120–140% LT with 1 min rest) or moderate-intensity CON (80–95% LT) training. Total training volume was matched between the two groups. After the training period, both groups had significant improvements in (12–14%; P<0.05) and the LT (7–10%; P<0.05), with no significant differences between groups. The INT group, however, had significantly greater improvements in βmin vitro (25%; 123±5–153±7 μmol H+·g muscle dm−1·pH−1; P<0.05) than the CON group (2%; 130±12–133±7 μmol H+·g muscle dm−1·pH−1, P>0.05). Our results show that when matched for training volume, high-intensity interval training above the LT results in similar improvements in and the LT, but greater improvements in βmin vitro than moderate-intensity continuous training below the LT. This suggests that training intensity is an important determinant of changes to βmin vitro