ORIGINAL RESEARCH article
Front. Sports Act. Living
Sec. Exercise Physiology
This article is part of the Research TopicImpact of Blood Flow Restriction Device Features and Methodological Considerations on Acute- and Longitudinal Responses to Blood Flow Restricted Exercise - Volume IIView all 4 articles
Effects of Autoregulated and Non-Autoregulated Blood Flow Restriction on Vastus Medialis Oblique Responses During Low-Load Resistance Exercise
Provisionally accepted
- 1University of Maryland Eastern Shore, Princess Anne, United States
- 2Salisbury University, Salisbury, United States
- 3PHITWELL, New York, United States
- 4The Human Performance Mechanic, New York, United States
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Introduction/Purpose Blood flow restriction (BFR) training is a viable strategy for inducing muscle hypertrophy and strength gains using low external loads. This study investigated the acute effects of autoregulated BFR (AR-BFR) and non-autoregulated BFR (NAR-BFR) using the Delfi Personalized Tourniquet System, and no BFR on vastus medialis obliquus (VMO) thickness, muscle oxygenation, hemoglobin concentration, and perceptual responses (rating of perceived exertion [RPE] and rating of perceived discomfort [RPD]). Methods Eighteen healthy adults (24.6 ± 2.3 years; 10 males, 8 females) performed a standardized single-leg wall squat protocol (1×30, 3×15 reps) under each condition in a randomized, crossover design. Results Both BFR conditions (AR-BFR and NAR-BFR) resulted in significantly greater increases in VMO thickness compared to the no BFR condition (p < 0.05), with no difference between the two BFR modalities (p > 0.05). Oxygen saturation significantly decreased across sets in both BFR conditions relative to no BFR (p < 0.05). However, AR-BFR initially maintained higher oxygen levels before declining to values comparable to those of NAR-BFR. Total hemoglobin levels were significantly elevated in both BFR conditions compared to no BFR (p < 0.05), with NAR-BFR producing the highest levels during the early sets. Both RPE and RPD were significantly greater in AR-BFR and NAR-BFR compared to no BFR (p < 0.05), with no significant differences between the two BFR protocols (p > 0.05). Conclusion These findings suggest that BFR training, regardless of autoregulated pressure application during exercise, produces acute physiological responses such as muscle swelling, localized hypoxia, and hemoconcentration that are conducive to initiating a stimulus that could elicit muscle hypertrophy in a training program. Although elevated perceptual demands accompanied these responses, the minimized mechanical joint stress supports the use of BFR as a clinically relevant alternative to high-load resistance training for individuals with limited tolerance to mechanical loading.
Keywords: autoregulation, muscle hypertrophy, Muscle thickness, near-infrared spectroscopy, Perceptual responses
Received: 24 Sep 2025; Accepted: 24 Nov 2025.
Copyright: © 2025 Moghaddam, Rabel, Werner and Rolnick. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Nicholas Rolnick
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