Autoregulation during blood flow restricted exercise offers no additional benefit on thigh muscle hypertrophy and strength adaptations in trained participants: a randomized within-subject 8-week trial

Background. With the increasing use of BFR, various cuff design features have emerged, potentially influencing training outcomes. One notable feature is autoregulation, which dynamically modifies tourniquet cuff pressure during muscle contractions to maintain a consistent applied pressure.

Objective. This study investigated the effects of autoregulated versus non-autoregulated blood flow restriction (BFR) training pressures on thigh muscle hypertrophy and strength.

Methods. Using a within-subjects randomized controlled trial design, twenty-one resistance-trained males (≥3 years of experience) completed twice-weekly sessions involving single-leg squats and knee extensions for 8 weeks. One lower limb was trained under autoregulated BFR (AUTO) and the other under non-autoregulated BFR (NONAUTO) conditions using the specific BFR device. Muscle strength (1RM), muscle thickness and cross-sectional area (CSA) of the rectus femoris and vastus lateralis were assessed pre- and post-intervention using ultrasonography. Ratings of perceived exertion (RPE) and discomfort (RPD) were also recorded at the end of weeks 1, 4 and 8.

Results. Both AUTO and NONAUTO conditions led to significant and comparable increases in muscle thickness and CSA across all measured sites of the thigh musculature, as well as improvements in 1RM for both exercises. RPE and RPD scores significantly decreased over time in both conditions, with no between-condition differences. No adverse events occurred in either condition. Autoregulated and non-autoregulated BFR training produced similar muscular hypertrophy and strength adaptations, and perceptual responses.

Conclusion. The current manuscript is the first ever to investigate the chronic effects of BFR training in autoregulated and non-autoregulated applications and is pioneering in this respect. These findings suggest autoregulation does not provide additional physiological benefits under controlled training conditions in the same individual.