High-intensity exercise decreases muscle buffer capacity via a decrease in protein buffering in human skeletal muscle.

We have previously reported an acute decrease in muscle buffer capacity (betam(in vitro)) following high-intensity exercise. The aim of this study was to identify which muscle buffers are affected by acute exercise and the effects of exercise type and a training intervention on these changes. Whole muscle and non-protein betam(in vitro) were measured in male endurance athletes (VO(2max) = 59.8 +/- 5.8 mL kg(-1) min(-1)), and before and after training in male, team-sport athletes (VO(2max) = 55.6 +/- 5.5 mL kg(-1) min(-1)). Biopsies were obtained at rest and immediately after either time-to-fatigue at 120% VO(2max) (endurance athletes) or repeated sprints (team-sport athletes). High-intensity exercise was associated with a significant decrease in betam(in vitro) in endurance-trained males (146 +/- 9 to 138 +/- 7 mmol H(+) x kg d.w.(-1) x pH(-1)), and in male team-sport athletes both before (139 +/- 9 to 131 +/- 7 mmol H(+) x kg d.w.(-1) x pH(-1)) and after training (152 +/- 11 to 142 +/- 9 mmol H(+) x kg d.w.(-1) x pH(-1)). There were no acute changes in non-protein buffering capacity. There was a significant increase in betam(in vitro) following training, but this did not alter the post-exercise decrease in betam(in vitro). In conclusion, high-intensity exercise decreased betam(in vitro) independent of exercise type or an interval-training intervention; this was largely explained by a decrease in protein buffering. These findings have important implications when examining training-induced changes in betam(in vitro). Resting and post-exercise muscle samples cannot be used interchangeably to determine betam(in vitro), and researchers must ensure that post-training measurements of betam(in vitro) are not influenced by an acute decrease caused by the final training bout.