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This investigation sought to assess whether single or repeated bouts of ischemic preconditioning (IPC) could improve oxyhemoglobin saturation (SpO2) and/or attenuate reductions in muscle tissue saturation index (TSI) during submaximal hypoxic exercise. Fifteen healthy young men completed submaximal graded exercise under four experimental conditions: 1) normoxia (NORM), 2) hypoxia (HYP) [oxygen fraction of inspired air (FIO2) = 0.14, ∼3,200 m], 3) hypoxia preceded by a single session of IPC (IPC1-HYP), and 4) hypoxia preceded by seven sessions of IPC, one a day for 7 consecutive days (IPC7-HYP). IPC7-HYP heightened minute ventilation (V̇e) at 80% HYP peak cycling power output (Wpeak) (+10.47 ± 3.35 L·min−1, P = 0.006), compared with HYP, as a function of increased breathing frequency. Both IPC1-HYP (+0.17 ± 0.04 L·min−1, P < 0.001) and IPC7-HYP (+0.16 ± 0.04 L·min−1, P < 0.001) elicited greater oxygen consumption (V̇o2) across exercise intensities compared with NORM, whereas V̇o2 was unchanged with HYP alone. SpO2 was unchanged by either IPC condition at any exercise intensity, yet the reduction of muscle TSI during resting hypoxic exposure was attenuated by IPC7-HYP (+9.9 ± 3.6%, P = 0.040) compared with HYP, likely as a function of reduced local oxygen extraction. Considering all exercise intensities, IPC7-HYP attenuated reductions of TSI with HYP (+6.4 ± 1.8%, P = 0.001). Seven days of IPC heightens ventilation, posing a threat to ventilatory efficiency, during high-intensity submaximal hypoxic exercise and attenuates reductions in hypoxic resting and exercise muscle oxygenation in healthy young men. A single session of IPC may be capable of modulating hypoxic ventilation; however, our present population was unable to demonstrate this with certainty. [ABSTRACT FROM AUTHOR]

Ischemic preconditioning (IPC) involves brief, repeated bouts of limb occlusion and reperfusion capable of improving exercise performance at least partially by enhancing local skeletal muscle oxygenation. This study sought to investigate the effect of a lower limb IPC protocol, with either a 5-min or 45-min post-application delay, on vastus lateralis tissue saturation index (TSI) and systemic cardiac hemodynamics at rest and during short-duration intense cycling. Twelve young adults randomly completed four interventions: IPC (at 220 mmHg) with 5-min delay (IPC5), IPC with 45-min delay (IPC45), SHAM (at 20 mmHg) with 5-min delay (SHAM5), and SHAM with 45-min delay (SHAM45). Following IPC intervention and recovery delay, participants completed 5, 60-s high-intensity (100% Wpeak) cycle sprints separated by 120-sec of active recovery (30% Wpeak). Compared to baseline, TSI immediately following IPC5, but pre-exercise, remained lower than the equivalent for IPC45 (−5.9 ± 1.5%, p =.002). IPC, imposed at least 45-min before the completion of five 60-s sprint cycling efforts, significantly enhanced TSI during active recovery between sprint intervals compared to a 5-min delay (6.6 ± 2.4%, p =.021), and identical SHAM conditions (SHAM5: 5.8 ± 2.2%, p =.024; SHAM45: 6.2 ± 2.5%, p =.029). A 45-min delay following IPC appears to provide heightened skeletal muscle metabolic rebound prior to intense sprint cycling as compared to a 5-min delay. Furthermore, IPC followed by a 45-min delay enhanced recovery of skeletal muscle oxygenation during low intensity active sprint recovery, despite an unchanged decline in skeletal muscle oxygenation during near-maximal sprinting efforts. [ABSTRACT FROM AUTHOR]