Comparison Of Autoregulated And Non-Autoregulated Blood Flow Restriction Training On Acute Muscular Morphological Adaptations: 460 (conference abstract)

Current literature has reported evidence of muscle damage and rhabdomyolysis with very strenuous blood flow restriction (BFR) resistance exercise. Purpose. To compare the effects of autoregulated BFR (A-BFR), non-autoregulated BFR (NA-BFR), and no BFR on acute morphological adaptations of vastus lateralis (VL). A-BFR cuff pressure was automatically adjusted throughout the range of motion as muscle contracting. NA-BFR devices did not adjust the pressure in the cuff for muscle contraction. Methods. Following a randomized familiarization, 20 adults (23 ± 5 years; 7 females) participated in 3 randomized treatment-order sessions with A-BFR, NA-BFR, and no BFR separated by 1-week washout periods. Participants performed four sets of wall squats to failure using 20% of 1-RM at 2-sec concentric/eccentric cadence and 1 min recovery between sets. Participants wore BFR cuffs at 60% of supine limb occlusion pressure (LOP) on top of their thighs. VL cross-sectional area (CSA) and echo intensity (EI) were assessed via ultrasound before and after each session. The scans were captured in the transverse plane at the mid-thigh of the right leg. Two-way ANOVAs were used for statistical analysis. Results. No significant time × treatment interaction (p > 0.05) was observed. However, there were significant main effects of treatment for CSA (p = 0.016) and EI (p = 0.019). Post hoc analyses showed significant differences between A-BFR and NA-BFR, while there were no other significant differences between treatments. Furthermore, significant main effects of time were observed in CSA (p = 0.000) and EI (p = 0.001). All treatments significantly (p < 0.05) increased CSA (A-BFR: 27.4 ± 6.8 to 29.7 ± 7.2 cm2, α%: 7.9 ± 3.3; NA-BFR: 27.8 ± 6.9 to 30.3 ± 7.3 cm2, α%: 8.5 ± 2.3; no BFR: 27.6 ± 6.7 to 29.8 ± 7.0 cm2, α%: 7.4 ± 3.4) and EI (A-BFR: 65.3 ± 10.5 to 67.5 ± 10.5 au, α%: 3.3 ± 4.9; NA-BFR: 68.6 ± 10.2 to 73.5 ± 11.0 au, α%: 6.1 ± 9.0; no BFR: 67.6 ± 9.6 to 70.8 ± 10.9 au, α%: 4.1 ± 6.6). Conclusion. Low-load resistance exercise to failure induces acute muscle swelling regardless of BFR. However, NA-BFR significantly increased CSA and EI compared to A-BFR. Since EI is inversely related to muscle quality, these findings suggest that autoregulated pressure in A-BFR can cause a lower fluid flux to the intracellular space and possibly less muscle damage and swelling than NA-BFR.