Targeted effect of ischemic preconditioning on the gas exchange threshold in healthy males and females

Ischemic preconditioning (IPC) appears to improve exercise performance although there is uncertainty about the intensity dependence of this effect. The present study sought to clarify effects of IPC on physiological responses at and below peak oxygen uptake, including the gas exchange threshold (GET). Ten male and female participants completed five cycling ramp tests (10 W/min) to failure, with the final two tests preceded by either IPC (4 × 5 min 220 mmHg bilateral leg occlusions) or SHAM (20 mmHg), in a randomised crossover design. The rates of O₂ uptake ( \(\dot{V}\) $\dot{V}$ O₂), carbon dioxide output ( \(\dot{V}\) $\dot{V}$ CO₂), and expired ventilation ( \(\dot{V}\) $\dot{V}$ _E) were measured at rest and throughout exercise. Exercise data were fitted using several functions to identify GET, two ventilatory thresholds and peak \(\dot{V}\) $\dot{V}$ O₂. IPC increased \(\dot{V}\) $\dot{V}$ O₂ at GET by ~ 9% (IPC: 1.89 ± 0.51 L/min, SHAM: 1.73 ± 0.56 L/min; p = 0.055) and power output at GET by ~ 11% (IPC: 133 ± 36 W, SHAM: 120 ± 39 W; p = 0.022). In addition, peak power output increased by 2.4% following IPC (IPC: 217 ± 50 W, SHAM: 212 ± 51 W; p = 0.052), but there was no significant effect of IPC on peak \(\dot{V}\) $\dot{V}$ O₂ (IPC: 2.87 ± 0.68 L/min, SHAM: 2.84 ± 0.73 L/min; p = 0.60) or the ventilatory thresholds. The present results suggest that IPC improves GET and peak power output but not peak \(\dot{V}\) $\dot{V}$ O₂ during a maximal graded test.