Acute Changes in Muscle Thickness and Perceptual Responses Following Different Blood Flow Restriction Applications.

We examined different applications of blood flow restriction (BFR) on acute changes in muscle thickness (MTH) and perceptual responses. Twelve females completed four applications of BFR consisting of continuous BFR (cBFR), intermittent during sets (iBFRsets), intermittent during rest (iBFRrest), and no BFR (nBFR). Participants completed a 75-repetition scheme (1 × 30, 3 × 15) of unilateral, isotonic, leg extension muscle actions performed at 20% of one-repetition maximum. MTH of the vastus lateralis (VL) and rectus femoris (RF) muscles prior to and following each condition were assessed. Ratings of perceived exertion (RPE) and perceptual pain were assessed following each set. Dependent variables were assessed with separate repeated-measures ANOVAs with a type I error of 5%. There were significant main effects of Time for VL (p < .001) and RF (p < .001) MTH, whereby it increased from pretest to posttest (Δ = 0.24 cm and Δ = 0.35 cm, respectively). For RPE, there was also a main effect of Time (p < .001), with RPE increasing progressively across the four sets (Δ = 2.64 au). Lastly, for Pain, there was a main effect of Time (p < .001) and Condition (p = .008), with pain increasingly progressively across the four sets (Δ = 2.50 au) and iBFRsets (5.85 ± 2.32 au) eliciting greater pain (+38%) responses than nBFR (4.23 ± 2.21 au). Collectively, there were significant acute increases in MTH and perceived exertion across all applications of BFR, but distinct perceptual pain responses (i.e. iBFRsets > nBFR).