Acute neuromuscular, cardiovascular, and muscle oxygenation responses to low-intensity aerobic interval exercises with blood flow restriction

Abstract

We investigated the influence of short- and long-interval cycling exercise with blood flow restriction (BFR) on neuromuscular fatigue, shear stress and muscle oxygenation, potent stimuli to BFR-training adaptations. During separate sessions, eight individuals performed short- (24 × 60 s/30 s; SI) or long-interval (12 × 120 s/60 s; LI) trials on a cycle ergometer, matched for total work. One leg exercised with (BFR-leg) and the other without (CTRL-leg) BFR. Quadriceps fatigue was quantified using pre- to post-interval changes in maximal voluntary contraction (MVC), potentiated twitch force (QT) and voluntary activation (VA). Shear rate was measured by Doppler ultrasound at cuff release post-intervals. Vastus lateralis tissue oxygenation was measured by near-infrared spectroscopy during exercise. Following the initial interval, significant (P < 0.05) declines in MVC and QT were found in both SI and LI, which were more pronounced in the BFR-leg, and accounted for approximately two-thirds of the total reduction at exercise termination. In the BFR-leg, reductions in MVC (-28 ± 15%), QT (-42 ± 17%), and VA (-15 ± 17%) were maximal at exercise termination and persisted up to 8 min post-exercise. Exercise-induced muscle deoxygenation was greater (P < 0.001) in the BFR-leg than CTRL-leg and perceived pain was more in LI than SI (P < 0.014). Cuff release triggered a significant (P < 0.001) shear rate increase which was consistent across trials. Exercise-induced neuromuscular fatigue in the BFR-leg exceeded that in the CTRL-leg and was predominantly of peripheral origin. BFR also resulted in diminished muscle oxygenation and elevated shear stress. Finally, short-interval trials resulted in comparable neuromuscular and haemodynamic responses with reduced perceived pain compared to long-intervals.

Keywords: arterial blood flow; blood flow restriction; central fatigue; interval exercise; interval training; peripheral fatigue; vascular occlusion.

FIGURE 1

Effect of short‐interval and long‐interval trials, with (BFR‐leg) or without (CTRL‐leg) blood flow restriction throughout exercise, on maximal voluntary contraction (MVC, a), on potentiated twitch peak force evoked by single (QT_single, b), 10 Hz (QT₁₀, c) and 100 Hz (QT₁₀₀, d) paired electrical stimulation, on prolonged low‐frequency force depression index (QT_10:100, e) and on voluntary activation (f). Statistically significant main effects and interaction effects are indicated on the graphs (n = 8). Note: there was no main effect of trial (i.e., short‐interval vs. long‐interval) in any of these variables. ^a P < 0.05 versus baseline in BFR‐legs and CTRL‐legs; ^b P < 0.05 versus the first quarter of the protocol (i.e., first‐, second‐ and/or third time‐matched neuromuscular assessment) in BFR‐legs; ^c P < 0.05 for BFR‐legs compared with CTRL‐legs.

FIGURE 2

Effect of short‐interval and long‐interval trials, with (BFR‐leg) or without (CTRL‐leg) blood flow restriction throughout the post‐exercise recovery period, on maximal voluntary contraction (MVC, a), on potentiated twitch peak force evoked by single (QT_single, b), 10 Hz (QT₁₀, c) and 100 Hz (QT₁₀₀, d) paired electrical stimulation, on prolonged low‐frequency force depression index (QT_10:100, e) and on voluntary activation (f). Statistically significant main effects and interaction effects are indicated on the graphs. ^a P < 0.05 versus 10 s post‐exercise in BFR‐legs; ^b P < 0.05 versus 10 s post‐exercise in CTRL‐legs; ^c P < 0.05 versus 1 and/or 2 min post‐exercise in BFR‐legs; ^d P < 0.05 versus 1 and/or 2 min post‐exercise in CTRL‐legs; ^e P < 0.05 versus 4 min post‐exercise in CTRL‐leg; ^f P < 0.05 for BFR‐legs compared with CTRL‐legs.

FIGURE 3

Effect of short‐interval and long‐interval trials, with (BFR‐leg) or without (CTRL‐leg) blood flow restriction, on deoxyhaemoglobin (a–c), oxyhaemoglobin (d–f) and total haemoglobin concentrations (g–i) during exercise (left column) and during between‐interval rest periods (central column). Data are also presented as Δ change from between‐interval rest periods to exercise (i.e., first exercise time point minus first between‐interval time point; right column). Statistically significant main effects and interaction effects are indicated on the graphs. ^a P < 0.05 versus baseline (Pre) in BFR‐legs; ^b P < 0.05 versus baseline (Pre) in CTRL‐legs.

FIGURE 4

Blood flow (a), shear rate (b) and vascular conductance (c) from the leg exercising with blood flow restriction (BFR‐leg) and mean arterial pressure (d) upon cuff release. Data are shown at rest (i.e, ‐5 min), during (represented by shaded areas) and after short‐interval (SI) and long‐interval (LI) trials. Statistically significant main effects and interaction effects are indicated on the graphs. ^a P < 0.05 versus baseline in SI and LI.