Low-Load Blood-Flow Restricted Resistance Training Improves Finger Flexor Muscle Function in Experienced Climbers: A Randomized Controlled Trial

PURPOSE: Low-load blood flow restriction training (LLBFRT) is a promising modality to improve muscle strength and endurance. In sport-climbing, LLBFRT may prove useful to reduce mechanical stress compared with traditional high-load resistance training (HLRT); however, previous climbing studies have failed to induce strength gains with LLBFRT, potentially due to insufficient training stimulus. This study thus aims to examine muscular adaptations to a 5-wk finger flexors LLBFRT program until failure, with comparison to HLRT. METHODS: Thirty-six advanced-to-elite climbers were randomly assigned to LLBFRT, HLRT, or a control group. Participants in LLBFRT and HLRT trained twice a week, at ~40% and ~75% of maximal voluntary contraction, respectively; cuffs were inflated at 60% of limb occlusion pressure in LLBFRT. The rate of perceived exertion, upper-limb discomfort, and finger pain intensity were measured during each session. Before and after intervention, finger flexor muscle thickness and strength were determined, while critical force and oxygenation were assessed during a fatiguing test. RESULTS: During training sessions, force-time integral was lower (-19%, P = 0.009) while mean upper-limb discomfort was greater (5 ± 2 vs 4 ± 2 units, P = 0.028) in LLBFRT versus HLRT. LLBFRT significantly improved finger flexors maximal voluntary contraction (+9 ± 8%, P = 0.009) and critical force (+22 ± 15%, P < 0.001). These gains were comparable to HLRT (+13 ± 11%, P = 0.006 and +24 ± 21%, P = 0.012, respectively). No significant changes were found in the control. CONCLUSIONS: Despite lower mechanical load, LLBFRT conducted until failure significantly improved finger flexor muscular capacities to a similar extent than HLRT in experienced sport-climbers. This training modality may therefore be of particular interest during overload periods.