Restoration of blood pH between repeated bouts of high-intensity exercise: effects of various active-recovery protocols

To determine which active-recovery protocol would reduce faster the high blood H+ and lactate concentrations produced by repeated bouts of high-intensity exercise (HIE). On three occasions, 11 moderately trained males performed 4 bouts (1.5 min) at 163% of their respiratory compensation threshold (RCT) interspersed with active-recovery: (1) 4.5 min pedalling at 24% RCT (SHORT); (2) 6 min at 18% RCT (MEDIUM); (3) 9 min at 12% RCT (LONG). The total work completed during recovery was the same in all three trials. Respiratory gases and arterialized-blood samples were obtained during exercise. At the end of exercise, LONG in comparison to SHORT and MEDIUM increased plasma pH (7.32 ± 0.02 vs. ~7.22 ± 0.03; P < 0.05), while reduced lactate concentration (8.5 ± 0.9 vs. ~10.9 ± 0.8 mM; P < 0.05). Ventilatory equivalent for CO2 was higher in LONG than SHORT and MEDIUM (31.4 ± 0.5 vs. ~29.6 ± 0.5; P < 0.05). Low-intensity prolonged recovery between repeated bouts of HIE maximized H+ and lactate removal likely by enhancing CO2 unloading.