Purpose: Recent studies have reported ischemic preconditioning (IPC) can acutely improve endurance exercise performance in athletes. However, placebo and nocebo effects have not been sufficiently controlled, and the effect on aerobic metabolism parameters that determine endurance performance (e.g., oxygen cost of running, lactate threshold, and maximal oxygen uptake [V˙O2max]) has been equivocal. Thus, we circumvented limitations from previous studies to test the effect of IPC on aerobic metabolism parameters and endurance performance in well-trained runners.
Methods: Eighteen runners (14 men/4 women) were submitted to three interventions, in random order: IPC; sham intervention (SHAM); and resting control (CT). Subjects were told both IPC and SHAM would improve performance compared to CT (i.e., similar placebo induction), and IPC would be harmless despite circulatory occlusion sensations (i.e., nocebo avoidance). Next, pulmonary ventilation and gas exchange, blood lactate concentration, and perceived effort were measured during a discontinuous incremental test on a treadmill. Then, a supramaximal test was used to verify the V˙O2max and assess endurance performance (i.e., time to exhaustion).
Results: Ventilation, oxygen uptake, carbon dioxide output, lactate concentration, and perceived effort were similar among IPC, SHAM, and CT throughout the discontinuous incremental test (P > 0.05). Oxygen cost of running, lactate threshold, and V˙O2max were also similar among interventions (P > 0.05). Time to exhaustion was longer after IPC (mean ± SEM, 165.34 ± 12.34 s) and SHAM (164.38 ± 11.71 s) than CT (143.98 ± 12.09 s; P = 0.02 and 0.03, respectively), but similar between IPC and SHAM (P = 1.00).
Conclusions: IPC did not change aerobic metabolism parameters, whereas improved endurance performance. The IPC improvement, however, did not surpass the effect of a placebo intervention.