Low-Load Blood Flow Restriction Training Enhances Brachial Blood Flow During Exercise but not Reactive Hyperemia in...

Low-load blood flow restriction training (LLBFRT) induces significant vascular stress, which is often associated with vascular remodeling, increased capillarization and muscle blood flow. These adaptations may be of interest to climbers as their endurance performance is limited by blood supply due to the isometric and intermittent nature of finger flexors (FD) contraction. This study, thus, aimed to assess vascular adaptations to a 5-week FD protocol using LLBFRT (n = 12, cuff pressure = 60% of the limb occlusion pressure) and compare these responses to those elicited by high-load resistance training (HLRT, n = 12) and no specific training (CON, n = 12) in male climbers. Participants in LLBFRT and HLRT trained twice a week, respectively at ~40% and ~75% of maximal voluntary contraction (MVC). Before and after the intervention, flow-mediated dilation (FMD), peak reactive hyperemia blood flow, brachial blood flow and muscle oxygenation (near-infrared spectroscopy) at rest and during contractions from 10% to 60% MVC were assessed using brachial doppler-ultrasound. Brachial blood flow across contraction intensities was significantly improved in LLBFRT (+19% ± 31%; p = 0.011, d = 0.5) but not in CON and HLRT. Oxy- and total hemoglobin concentrations decreased less during contraction following LLBFRT while did not change following CON and HLRT. Reactive hyperemia and FMD were not altered by any training modality. In conclusion, despite no difference with HLRT, LLBFRT was the only protocol which increased significantly blood flow of the feeding artery and O₂ availability during finger flexor low-intensity contractions. However, these adaptations were not accompanied by modifications of macrovascular structure or endothelial function.