High-intensity interval training with blood-flow restriction enhances sprint and maximal aerobic power in male endurance athletes

High-intensity interval training (HIIT) can improve endurance performance. Purpose: We investigated the concurrent impact of HIIT and blood-flow restriction (BFR) as a novel approach to further enhance maximal aerobic and anaerobic physiology and performances in trained athletes. Methods: In a randomized controlled trial, eighteen endurance-trained males (V ̇O2peak 65.6±5.1 ml.min-1.kg-1) included three sessions of HIIT per week (sets of 15-s efforts at 100% maximal aerobic power, interspersed by 15-s recovery) into their usual training for three weeks, either with restriction imposed on both lower limbs at 50-70% of arterial occlusion pressure (BFR group, n=10) or without (CTL group, n=8), and were tested for sprint and endurance exercise performance. Results: The total mechanical work developed during a 30-sec Wingate test increased only in BFR (3.6%, P=0.02). During the Wingate, changes in near-infrared spectroscopy-derived vastus lateralis muscle oxygenation (Δ(deoxy[Hb+Mb]), % arterial occlusion) were attenuated after BFR training (-8.8%, P=0.04). The maximal aerobic power measured during an incremental cycling test increased only in BFR (4.5%, P=0.0004), but there was no change in V ̇O2peak among groups. Both groups improved 5-km cycling time trial performance, but BFR displayed a concomitant greater elevation in [H+] (11%, P=0.02). Changes in other blood variables (e.g., pH, lactate, bicarbonate and potassium ion concentration, hemoglobin) were not different between groups. Conclusion: Combining short-duration HIIT performed at 100% aerobic power with BFR elicited greater changes in sprint performance and maximal aerobic power in endurance athletes, associated with locomotor muscle metabolic adaptations but no meaningful effect on cardiorespiratory fitness.