The effect of blood-flow-restricted interval training on lactate and H⁺ dynamics during dynamic exercise in man

Aim: To assess how blood-flow-restricted (BFR) interval-training affects the capacity of the leg muscles for pH regulation during dynamic exercise in physically-trained men.

Methods: Ten men (age: 25 ±4y; V̇O_2max: 50 ±5mL∙kg^-1∙min^-1) completed a 6-wk interval-cycling intervention (INT) with one leg under BFR (BFR-leg; ~180 mmHg) and the other without BFR (CON-leg). Before and after INT, thigh net H⁺-release (lactate-dependent, lactate-independent, and sum) and blood acid/base variables, were measured during knee-extensor-exercise at 25% (Ex25) and 90% (Ex90) of incremental-peak-power-output. A muscle biopsy was collected before and after Ex90 to determine pH, lactate, and density of H+ -transport/buffering systems.

Results: After INT, net H⁺-release (BFR-leg: 15±2; CON-leg: 13±3; mmol·min^-1; Mean±95%CI), net lactate-independent H+ -release (BFR-leg: 8±1; CON-leg: 4±1; mmol·min^-1), and net lactate-dependent H⁺-release (BFR-leg: 9±3; CON-leg: 10±3; mmol·min^-1) were similar between legs during Ex90 (p>0.05), despite a ~142% lower muscle-intracellular-to-interstitial lactate-gradient in BFR-leg (-3±4 vs. 6±6 mmol·L^-1 ; p<0.05). In recovery from Ex90, net lactate-dependent H⁺-efflux decreased in BFR-leg with INT (p<0.05 vs. CON-leg) due to lowered muscle lactate production (~58% vs. CON-leg, p<0.05). Net H⁺ -gradient was not different between legs (~19%, p>0.05; BFR-leg: 48±30; CON-leg: 44±23; mmol·L^-1). In BFR-leg, NHE1-density was higher than in CON-leg (~45%; p<0.05) and correlated with total-net H⁺-release (r=0.71; p=0.031) and lactate-independent H⁺-release (r=0.74; p=0.023) after INT, where arterial [HCO₃^-] and standard-base-excess in Ex25 were higher in BFR-leg than CON-leg.

Conclusion: Compared to a training control, BFR-interval training increases the capacity for pH-regulation during dynamic exercise mainly via enhancement of muscle lactate-dependent H⁺-transport function and blood H⁺-buffering capacity.