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

International audienceWe have previously reported an acute decrease in muscle buffer capacity (βm 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 βm 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 βm in vitro in endurance-trained males (146±9 to 138±7 mmol H + ·kg d.w. −1 ·pH −1), and in male team-sport athletes both before (139±9 to 131±7 mmol H + ·kg d.w. −1 ·pH −1) and after training (152±11 to 142±9 mmol H + ·kg d.w. −1 ·pH −1). There were no acute changes in non-protein buffering capacity. There was a significant increase in βm in vitro following training, but this did not alter the post-exercise decrease in βm in vitro. In conclusion, high-intensity exercise decreased βm 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 βm in vitro. Resting and post-exercise muscle samples cannot be used interchangeably to determine βm in vitro , and researchers must ensure that post-training measurements of βm in vitro are not influenced by an acute decrease caused by the final training bout