The Influence Of Blood Flow Restriction And Proximity To Failure On Changes In Muscle Strength

Low-load resistance exercise to failure with and without blood flow restriction (BFR) results in similar changes in muscle strength. Whether strength gain is impacted by applying BFR to submaximal resistance exercise remains largely unknown. It is common to employ a pre-determined number of repetitions across all individuals. However, this approach does not account for each individual’s local muscular endurance, making it difficult to draw a definitive conclusion. It is also unclear if the cross-education of strength is observed with sub-maximal BFR isotonic exercise. PURPOSE: To examine the effects of unilateral submaximal resistance exercise with BFR on muscle strength and cross-education while accounting for proximity to failure. METHODS: 130 participants (18-35 years) were randomly assigned to one of four groups: low-load submaximal elbow flexion exercise 1) with BFR (LL + BFR, n = 32), 2) without BFR (i.e., matched for a % of repetition-to-failure) (LL, n = 33), 3) to failure (LL-FAIL, n = 33), and 4) a non-exercise control group (CON, n = 32). All exercise groups completed 18 training sessions (6 weeks). The submaximal groups performed two sets of bicep curl exercise with (80% of arterial occlusion pressure) or without BFR. The repetitions completed were based on the muscular endurance performance with BFR during the pre-testing visit. The LL-FAIL group performed two sets to failure. The prescribed load was maintained throughout the training (30% 1RM). Changes in maximal strength (1RM) were compared using Bayes Factors for Informative Hypotheses (BAIN). The ANCOVA function of BAIN was used with the pre-values serving as the covariate. Data are presented as mean (SE). RESULTS: Low-load exercise increased strength in the training arm over CON, with no difference between training groups (posterior probability of 0.8). There were increases of 0.51 SE 0.17, 0.54 SE 0.17, 0.40 SE 0.17 kg for the LL, LL + BFR, and LL-FAIL groups, respectively. There was no evidence for cross-education of strength with the null model being the most likely (posterior probability of 0.75). CONCLUSION: Increase in 1RM strength with low-load exercise was not dependent on the application of BFR nor the proximity to failure. In contrast to data on isometric exercise, BFR training did not induce cross-education with isotonic exercise.