Cycling with blood flow restriction improves performance and muscle K⁺ regulation and alters the effect of antioxidant infusion in humans

Key points: Training with blood flow restriction (BFR) is a well-recognised strategy to promote muscle hypertrophy and strength. However, its potential to enhance muscle function during sustained, intense exercise remains largely unexplored.

Here, we report that interval training with BFR augments improvements in performance and reduces net K⁺ release from contracting muscles during high-intensity exercise in active men.

A better K⁺ regulation after BFR-training is associated with an elevated blood flow to exercising muscles and altered muscle antioxidant function, as indicated by a higher reduced to oxidised glutathione (GSH:GSSG) ratio, compared to control, and an increased thigh net K⁺ release during intense exercise with concomitant antioxidant infusion.

Training with BFR also invoked fibre-type specific adaptations in abundance of Na⁺,K⁺-ATPase isoforms (α₁ , β₁ , phospholemman/FXYD1).

Thus, BFR-training enhances performance and K⁺ regulation during intense exercise, which may be due to adaptations in antioxidant function, blood flow, and Na⁺,K⁺-ATPase-isoform abundance at the fibre-type level.

Abstract: We examined if blood flow restriction (BFR) augments training-induced improvements in K⁺ regulation and performance during intense exercise in men, and if these adaptations are associated with an altered muscle antioxidant function, blood flow, and/or with fibre type-dependent changes in Na⁺,K⁺-ATPase-isoform abundance. Ten recreationally-active men (25 ± 4 y, 49.7 ± 5.3 mL kg^-1 min^-1) performed 6 weeks of interval cycling, where one leg trained without (control; CON-leg) and the other with BFR (BFR-leg, pressure: ∼180 mmHg). Before and after training, femoral arterial and venous K⁺ concentrations and artery blood flow were measured during single-leg knee-extensor exercise at 25% (Ex1) and 90% of thigh incremental peak power (Ex2) with intravenous infusion of N-acetylcysteine (NAC) or placebo (saline), and a resting muscle biopsy was collected. After training, performance increased more in BFR-leg (23%) than in CON-leg (12%, p<0.05), whereas K⁺ release during Ex2 was attenuated only from BFR-leg (p < 0.05). Muscle GSH:GSSG ratio at rest and blood flow during exercise were higher in BFR-leg than in CON-leg after training (p < 0.05). After training, NAC increased resting muscle GSH concentration and thigh net K⁺ release during Ex2 only in BFR-leg (p < 0.05), whilst the abundance of Na⁺,K⁺-ATPase-isoform α₁ in type-II (51%), β₁ in type-I (33%), and FXYD1 in type-I (108%) and type-II (60%) fibres was higher in BFR-leg than in CON-leg (p < 0.05). Thus, training with BFR elicited greater improvements in performance and reduced thigh K⁺ release during intense exercise, which were associated with adaptations in muscle antioxidant function, blood flow, and Na⁺,K⁺-ATPase-isoform abundance at the fibre-type level.