High‐intensity Interval Training Combined With Blood‐flow Restriction Predominantly Alters Anaerobic Capacity in Endurance‐trained Athletes

Blood-flow restriction (BFR) training has gained popularity amongst athletes and sport practitioners to enhance training adaptations and performance. However, BFR has typically been associated with low-intensity exercise, and there is still limited evidence of its impact when combined with high-intensity training. This study investigated the impact of high-intensity interval training (HIIT) with concurrent BFR on anaerobic and aerobic physical capacities and key physiological responses. In a pre-post, parallel-groups design, fifteen endurance-trained males (VO2 max 65.0±4.8 mL/min/kg) included three sessions of HIIT per week (sets of 15 s ON/15 s OFF at 100% maximal aerobic power) into their usual training for three weeks either with (BFR group, n=9) or without restriction (CTL group, n=6). In BFR, cuffs were worn proximal on both quadriceps and inflated progressively from 50 to 70% of arterial occlusion pressure across training weeks. Before and after training, athletes completed a maximal incremental step cycling test, a Wingate anaerobic test (WAnT) and a 5-km cycling time trial. Blood samples were drawn during the time trials. Maximal aerobic power increased in BFR (364.8±60.7 vs 383.4±61.4 watts, p=0.003, Cohen's effect size ES 0.27) but not in CTL (381.2±62.1 vs 385.5±64.4 watts, p=0.45, ES 0.05). Concomitantly, mean power output achieved during the WAnt also increased with BFR (23.8±4.0 vs 24.6±4.1 kJ, p=0.08, ES 0.28) but not in CTL (23.4±2.5 vs 23.4±2.4 kJ, p=0.95, ES 0.01). However, there was no change between groups in VO2 max (BFR: 0.86% vs CTL: 1.77%, ES -0.15) and in both the mean power output (BFR: 1.81% vs CTL: 6.51%, ES -0.21) and completion time (BFR: -0.69% vs CTL: -2.55%, ES -0.21) of the 5-km time trial. During the time trial, BFR also induced greater changes in pH (BFR: -0.05 vs CTL: -0.03 units, ES -0.43) and base excess (BFR: -1.55 vs CTL: -0.70 units, ES -0.37), and lowered the potassium ion concentration (BFR: -0.55 vs CTL: 0.44 mmol/L, ES -0.63). There was no change between groups in lactate production from pre- to post-training. These findings suggest that short-term HIIT combined with BFR improved anaerobic capacity in endurance-trained athletes without meaningful effect on endurance exercise performance.