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

Abstract

We examined if blood flow restriction (BFR) would augment training-induced improvements in muscle K+ handling and performance during intense exercise in men, and if these adaptations would be associated with an effect of muscle antioxidant function on thigh K+ release and with fibre type-dependent modulation of Na+,K+-ATPase-isoform abundance and FXYD1 phosphorylation. 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 leg with BFR (BFR-leg, pressure: 178 mmHg). Before and after training, catheters were inserted into the femoral artery and vein, and blood flow was assessed during single-leg knee-extensions at 25% (Ex1) and 90% of leg peak aerobic power (Ex2) with intravenous infusion of N-acetylcysteine (NAC) or saline (placebo), and a resting muscle biopsy was collected. After training, performance during exhaustive exercise increased to a greater extent in BFR-leg (23%) than in CON-leg (12%, p0.05). After training, this effect was blunted in BFR-leg (p<0.05), whilst the abundance of Na+,K+-ATPase-isoform 1 in type-II (51%), {beta}1 in type-I (33%), and FXYD1 in type-I (108%) and type-II (60%) fibres was higher in BFR-leg (p<0.05; vs. CON-leg). Thus, interval training with BFR elicits greater improvements in performance and reduces muscle net K+ release during intense exercise, which may be caused by elevated ROS scavenging and fibre type-dependent increases in Na+,K+-ATPase-isoform abundance.\n\nKey pointsO_LIHere, we provide evidence that reactive oxygen species (ROS) play a role in regulating K+ homeostasis in the untrained musculature of humans, as indicated by attenuated thigh K+ efflux during exercise with concomitant antioxidant infusion.\nC_LIO_LIWe also demonstrate that interval training with blood flow restriction (BFR) augments improvements in performance and reduces K+ release from contracting muscles during intense exercise\nC_LIO_LIThe effect of training with BFR on muscle K+ handling appears to be partly mediated by increasing the protection against ROS, since the effect of antioxidant infusion was blunted after training with restricted blood flow.\nC_LIO_LIFurther, training with BFR resulted in higher abundance of Na+,K+-ATPase-isoform 1 in type-II (51%), {beta}1 in type-I (33%), and FXYD1 in type-I (108%) and type-II (60%) muscle fibres. This suggests fibre type-specific adaptations in Na+,K+-ATPase-isoform content are also important for improvements in muscle K+ handling by training with BFR in humans.\nC_LI