Blood flow restriction does not result in prolonged decrements in torque

Abstract

We sought to determine if blood flow restriction (BFR) by itself or in combination with exercise would result in prolonged decrements in torque when using restriction pressures relative to the participants' limb size. Sixteen participants were randomized into Experiment A (n = 9) or Experiment B (n = 7). Experiment A participants performed unilateral knee extensions at 30 % of their one repetition maximum (1RM) with moderate blood flow restriction on one leg (BFR + Exercise) and exercised the other leg without BFR (CON + Exercise). Experiment B participants rested for 4 min with BFR applied to one leg and rested for 4 min without any treatment on the other leg (CON). Maximal voluntary isometric torque (MVC) was measured before and immediately after the exercise or 4 min of rest, 1 h post, and 24 h post. Ratings of perceived exertion (RPE) and discomfort were taken before and after each set. MVC was significantly reduced following both exercise conditions with BFR + Exercise having the largest reduction in torque. However, torque quickly recovered by 1 h post exercise and was back to baseline by 24 h. No changes in torque were observed in Experiment B. RPE and discomfort were rated consistently higher for those in the BFR + Exercise and BFR conditions compared to control. In conclusion, BFR + Exercise does not result in prolonged decrements in torque. The acute changes in torque are due to fatigue and quickly recover back to baseline within 24 h of exercise. In addition, BFR in the absence of exercise has no effect on torque at any time point.