Tissue Oxygenation in Response to Different Relative Levels of Blood-Flow Restricted Exercise.

Joana F Reis,Francisco B Alves,Maria J Valamatos,Pedro Mil-Homens,Pedro Fatela,Joao R Vaz,Jorge Infante,Goncalo V Mendonca

doi:10.3389/fphys.2019.00407

Joana F Reis, Francisco B Alves + Show 6 more

Open Access

https://doi.org/10.3389/fphys.2019.00407

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Abstract

Blood flow restrictive (BFR) exercise elicits a localized hypoxic environment compatible with greater metabolic stress. We intended to compare the acute changes in muscle microvascular oxygenation following low-intensity knee extension exercise, combined with different levels of BFR. Thirteen active young men (age: 23.8 ± 5.4 years) were tested for unilateral knee extension exercise (30 + 15 + 15 + 15 reps at 20% one repetition maximum) on four different conditions: no-BFR (NOBFR), 40, 60, and 80% of arterial occlusion pressure (AOP). Deoxyhemoglobin+myoglobin concentration Deoxy[Hb+Mb], total hemoglobin [T(H+Mb)] and tissue oxygen saturation [TOI] were measured on the vastus lateralis muscle using near-infrared spectroscopy (NIMO, Nirox srl, Brescia, Italy). The magnitude of change in Deoxy[Hb+Mb]during exercise was similar between 60 and 80% AOP. Overall, compared to that seen during 60 and 80% AOP, NOBFR as well as 40% AOP resulted in a lower magnitude of change in Deoxy[Hb+Mb] (p < 0.05). While the oxygen extraction decreased during each inter-set resting interval in NOBFR and 40% AOP, this was not the case for 60 or 80% AOP. Additionally, TOI values obtained during recovery from each set of exercise were similarly affected by all conditions. Finally, our data also show that, when performed at higher restrictive values (60 and 80%), BFR exercise increases total Deoxy[Hb+Mb] extraction (p < 0.05). Taken together, we provide evidence that BFR is effective for increasing deoxygenation and reducing tissue oxygenation during low-intensity exercise. We also showed that when using low loads, a relative pressure above 40% of the AOP at rest is required to elicit changes in microvascular oxygenation compared with the same exercise with unrestricted conditions.

Highlights

The chronic effect of using tourniquet cuffs to restrict muscle blood flow during resistance exercise on muscle size and strength are well established in the available literature (Loenneke et al, 2012; Slysz et al, 2016)
Peak torque was similar between pre- and post-exercise time points in all conditions, except for 80% arterial occlusion pressure (AOP)
Deoxy[Hb+Mb] values were consistently lower during NOBFR and 40% AOP when compared to that seen at 60 and 80% AOP throughout all time points (p < 0.05)

Summary

Introduction

The chronic effect of using tourniquet cuffs to restrict muscle blood flow during resistance exercise on muscle size and strength are well established in the available literature (Loenneke et al, 2012; Slysz et al, 2016). Several studies have shown that performing BFR exercise with 20% of 1RM induces the same or even greater fatiguing stimulus when compared with high intensity exercise training (Takarada et al, 2000; Cook et al, 2007) It can be used in multiple exercise settings, when high intensity resistance exercise is not recommended (Cook et al, 2007). Since BFR exercise is typically performed using light loads, metabolic stress is believed to be largely responsible for enhancements in both muscle size and strength after training (Takarada et al, 2000, 2002)

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