Low-load Resistance Training To Failure Enhances Ischemic Local Muscular Endurance Capacity Over Submaximal Low-load Exercise With Blood Flow Restriction

Local muscular endurance (LME) describes the capacity of a muscle to repeatedly develop a certain degree of tension and is often measured by the number of repetitions to task failure using a percentage of one-repetition maximum (1RM) strength. Low-load resistance training performed to task failure with and without blood flow restriction (BFR) has been shown to similarly increase LME. However, the effects of submaximal (i.e., non-failure) low-load training with and without BFR on ischemic LME (I-LME; repetitions to task failure under ischemia) have not been extensively studied. PURPOSE: To examine the effects of submaximal low-load resistance training (30% 1RM) with and without BFR on changes in I-LME compared to low-load training to task failure. METHODS: A between-group, repeated measures design in which 130 participants (18-35 years) were randomly allocated to 1 of 4 groups was used: (1) submaximal low-load exercise with BFR applied at 80% arterial occlusion (LL + BFR, n = 32), (2) submaximal low-load exercise without BFR (LL, n = 33); (3) low-load exercise to task failure (LL + FAIL, n = 33); (4) time-matched non-exercise control (CON, n = 32). The training groups performed 2 sets of unilateral elbow flexions (dominant arm) 3x/week, for 6-weeks. The CON group only completed pre- and post-measurements of 1RM and I-LME testing, which involved 1 set of 30% pre-1RM unilateral elbow flexions (dominant arm) to task failure with BFR (80% arterial occlusion) at a cadence of 2 s/rep (1 s concentric/eccentric). ANCOVA function of BAIN was used to compare the mean change scores for the number of repetitions under ischemia. Data are presented as mean (SE). RESULTS: All training groups saw an increase in I-LME compared to CON (posterior probability of 0.83). The LL + FAIL observed the greatest change (17.1 SE 2.2 reps) followed by LL + BFR (9.8 SE 2.2 reps), and then LL (4.2 SE 2.2 reps). The change in number of repetitions completed during training (first to final session) was 9, 8, and 253 for LL, LL + BFR, and LL + FAIL, respectively. CONCLUSION: The current data suggest that low-load resistance exercise can effectively increase I-LME. However, greater adaptations occurred for the groups training similar to how testing was performed. Future work might include a group that exercises to task failure under BFR to see if I-LME can be increased further.