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

Abstract

Introduction Ischemic preconditioning (IPC) before exercise has been shown to be a novel approach to improve performance in different exercise modes in normoxia (NORM). Few studies have been conducted examining potential mechanisms behind these improvements, and less has been done examining its influence during exercise in hypoxia (HYP). Oxygen uptake and extraction kinetics are factors that have been implicated as possible determinants 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 NORM and HYP. Methods Thirteen men (age, 24 ± 7 yr; V˙O2max, 63.1 ± 5.1 mL·kg−1·min−1) participated in the study. Subjects completed trials of each combination of normobaric HYP (FiO2 = 0.16, simulating ~8000 ft/2500 m) or NORM (FiO2 = 0.21) with preexercise IPC protocol (4 × 5 min at 220 mm Hg) or SHAM procedure. Trials included submaximal constant load cycle exercise bouts (power outputs of 15% below gas exchange threshold, and 85% of V˙O2max), and a 5-km cycling performance TT. Results Ischemic preconditioning significantly improved 5-km TT time in NORM by 0.9% ± 1.8% compared with SHAM (IPC, 491.2 ± 35.2 s vs SHAM, 495.9 ± 36.0 s; P < 0.05). Ischemic preconditioning did not alter 5-km TT performance times in HYP (P = 0.231). Ischemic preconditioning did, however, improve tissue oxygen extraction in HYP (deoxygenated hemoglobin/myoglobin: IPC, 21.23 ± 10.95 μM; SHAM, 19.93 ± 9.91 μM; P < 0.05) during moderate-intensity exercise. Conclusions Our data confirm that IPC is an effective ergogenic aid for athletes performing 5-km cycling TT bouts in NORM. Ischemic preconditioning did mitigate the declines in tissue oxygen during moderate-intensity exercise in HYP, but this did not translate to a significant effect on mean group performance. These data suggest that IPC may be of benefit for athletes training and competing in NORM.

Active Preconditioning With Blood Flow Restriction or/and Systemic Hypoxic Exposure Does Not Improve Repeated Sprint Cycling Performance

“…First, Δ[HHb] was greater during RSE in T following IPC. This result is similar to a recent study where increased oxygen extraction (i.e., greater deoxygenated hemoglobin) was observed during a 5 km time-trial in hypoxia following IPC treatment (Wiggins et al, 2019). A larger Δ[HHb] is taken to reflect a greater O 2 utilization in the exercising muscle (Paradis-Deschênes et al, 2016).…”

Ischemic preconditioning of the muscle reduces the metaboreflex response of the knee extensors

“…Kilding et al ( 2018 ) reported a reduction in V̇O 2 slow component during heavy intensity cycling exercise. Wiggins et al ( 2019 ) reported a significant improvement in deoxyhemoglobin and deoxymyoglobin primary component amplitude during cycling 15% below gas exchange ratio in hypoxia following IP. Based on these studies, it is plausible that IP might also affect the kinetics of the hemodynamic response; however, to the best of our knowledge, no studies have done so.…”

Ischemic Preconditioning Enhances Aerobic Adaptations to Sprint-Interval Training in Athletes Without Altering Systemic Hypoxic Signaling and Immune Function

“…This non-invasive technique, involving repeated episodes of muscle ischemia followed by reperfusion at rest, induces transient peripheral hypoxia and can acutely improve maximal exercise capacity (Cruz et al, 2016 ; Salvador et al, 2016 ). For example, IPC improved mean power output during a 60 s cycling sprint, with a greater increase at exercise onset (Cruz et al, 2016 ), and time-trial (TT) performance in cyclists (Paradis-Deschênes et al, 2018 ; Wiggins et al, 2018 ). However, the precise physiological responses and mechanisms associated with these enhancements are still equivocal.…”