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; V˙O2max : 50 ± 5 mL∙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 > .05), despite a ~142% lower muscle intracellular-to-interstitial lactate gradient in BFR-leg (-3 ± 4 vs 6 ± 6 mmol·L-1 ; P < .05). In recovery from Ex90, net lactate-dependent H+ efflux decreased in BFR-leg with INT (P < .05 vs CON-leg) owing to lowered muscle lactate production (~58% vs CON-leg, P < .05). Net H+ gradient was not different between legs (~19%, P > .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 < .05) and correlated with total-net H+ -release (r = 0.71; P = .031) and lactate-independent H+ release (r = 0.74; P = .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.