Ischemic Preconditioning, O2 Kinetics, and Performance in Normoxia and Hypoxia

INTRODUCTION Ischemic preconditioning (IPC) prior to exercise has been shown to be a novel approach to improve performance in different exercise modes in normoxia. Few studies have been conducted examining potential mechanisms behind these improvements, and less has been done examining its influence during exercise in hypoxia. Oxygen uptake and extraction kinetics are factors that have been implicated as possible determinant of cycling performance. We hypothesized that IPC would lead to improvements in oxygen extraction and peripheral blood flow kinetics, and this would translate to improvements in cycling time trial (TT) performance in both normoxia and hypoxia. METHODS Thirteen men (age=24±7 years, V[Combining Dot Above]O2max=63.1±5.1 ml·kg-1·min-1) participated in the study. Subjects completed trials of each combination of normobaric hypoxia (HYP, FiO2 = 0.16, simulating ~8000ft/2500m) or normoxia (NORM, FiO2=0.21) with pre-exercise IPC protocol (4x5min at 220mmHg) or SHAM procedure. Trials included submaximal constant load cycle exercise bouts (power outputs of 15% below gas exchange threshold, and 85% of V[Combining Dot Above]O2max), and a 5km cycling performance TT. RESULTS IPC significantly improved 5km TT time in NORM by 0.9±1.8% compared to SHAM (IPC: 491.2±35.2s vs. SHAM: 495.9±36.0s, P

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