(31) EFFECTS OF LOW-INTENSITY AEROBIC TRAINING WITH BLOOD FLOW RESTRICTION ON AEROBIC FITNESS, MUSCULAR STRENGTH AND POWER, AND MUSCLE OXIDATIVE CAPACITY

Purpose: The purpose of this study was to examine the effect of low-intensity aerobic training with (BFR) and without (CONT) blood flow restriction (BFR) on aerobic fitness, muscle strength, muscle power, and muscle oxidative capacity (MOC). Methods: Participants were randomized into CONT or BFR groups and completed low-intensity interval training on a cycle ergometer. The only difference between groups was the application of BFR. Over four weeks, 10 training sessions were completed. Week 1 included pre-testing (PRE) and 2 sessions with 5 work intervals. Weeks 2 and 3 had 3 sessions each, with 6 and 8 work intervals, respectively. Week 4 included 2 sessions with 10 work intervals and post-testing (POST). Each training session consisted of a 4-minute warmup at 20 watts, followed by 2-minute work intervals at 70% of the gas exchange threshold, interspersed with 1-minute recovery intervals at 20 watts, and a cooldown. For the BFR group, cuffs were inflated to 80% of limb occlusion pressure during work intervals and deflated during recovery. The control group did not wear BFR cuffs. Outcome measurements were determined in the PRE and POST phases. MOC was determined from eight arterial occlusions with deoxyhemoglobin measured by near-infrared spectroscopy at the vastus lateralis. A mono-exponential decay curve was fitted to determine the time constant (τ), indicative of MOC (τMOC). Three maximum isometric knee extensions on the dominant leg were performed; the highest torque was reported for muscle strength. Muscle power was assessed from three maximal vertical jumps measured by a linear position transducer, recording the greatest vertical jump height. Aerobic fitness was determined from a graded exercise test to maximal exertion while gas exchange was measured continuously, and the highest oxygen consumption (VO2max) was recorded. Two-way (group x time) repeated measures ANOVAs analyzed variables with significance established if p ≤ 0.05. Results: The work intervals were 49.0 ± 20.9 W (48.1 ± 1.8% of VO2max) in BFR and 51.3 ± 11.8 W (43.1 ± 2.0% of VO2max) in CONT (p = 0.88). There was no change in τMOC from PRE to POST in BFR (29.6 ± 20.3 s vs. 29.7 ± 22.5 s) and CONT (34.58 ± 11.4 s vs. 32.9 ± 8.2 s). The differences in τMOC between groups were not significant. VO2max increased from PRE (2.48 ± 0.50 L/min) to POST (2.63 ± 0.53 L/min) in BFR (p = 0.033), but there was no change in CONT (POST = 2.81 ± 0.36 L/min; p = 0.67). There were no significant differences in VO2max between BFR and CONT at PRE (p = 0.338) or POST (p = 0.598). In BFR, there was no change from PRE to POST in muscle strength (188.9 ± 27.8 N∙m vs. 209.3 ± 32.2 N∙m) and vertical jump (0.36 ± 0.04 m vs. 0.33 ± 0.04 m). Similarly, there was no change from PRE to POST in muscle strength (257.1 ± 26.3 N∙m vs. 192.1 ± 38.8 N∙m) or vertical jump (0.32 ± 0.11 m vs. 0.34 ± 0.08 m) in CONT. There was a main effect of group for muscle strength (p = 0.05), but no differences between groups for vertical jump. Conclusions: Four weeks of low-intensity aerobic training with BFR increased aerobic fitness. However, the adaptations may be cardiovascular because no changes were observed within the muscle (i.e., MOC, muscular strength, and power). Practical Applications: Athletes can incorporate BFR into their training regimens to enhance aerobic capacity without the need for high-intensity training sessions, which can help reduce the risk of overtraining. However, greater stimulus or longer training would be needed to mediate changes within the musculature. Acknowledgements: Conway Medical Center College of Health and Human Performance Research Fellowship