Acute physiological and perceptual responses to three blood flow restricted interval exercise protocols: a randomised...

Blood flow restriction (BFR) may enhance the acute training stimulus of exercise. This study examined acute physiological and perceptual responses to three lower-limb BFR + interval exercise protocols. Twenty-four club/university male athletes (age 25 ± 3.5, V̇O_2max 47.0 ± 5.5 mL∙kg∙min^{- 1}) completed four experimental conditions in a randomised crossover manner: (i) high-intensity control (HI) - 100% maximal aerobic power (W_max); (ii) high-intensity recovery occlusion (HIRO) - 100% W_max, 80% limb occlusion pressure (LOP) during rest; (iii) moderate-intensity low occlusion (MILO) - 70% W_max, 50% LOP during exercise; and (iv) moderate-intensity high occlusion (MIHO) - 70% W_max, 80% LOP during exercise. All interval exercise protocols were three sets of five × 30 s cycling, 30 s unloaded active recovery with 3 min seated rest between sets. During recovery, HIRO condition indicated lower tissue saturation index, higher deoxyhaemoglobin, oxyhaemoglobin and total haemoglobin levels than other conditions (all p < 0.05). HIRO exhibited significantly higher heart rate (HR) from set 2 and blood lactate (bLa) at 5 min post-exercise than other conditions (all p < 0.05). Higher vastus lateralis muscle activity was exhibited on the last exercise repetition of HIRO than HI (p < 0.05). MIHO elicited significantly higher deoxygenation, lower muscle activation but similar HR and bLa than HI during exercise; and higher perceived pain and exertion than other conditions (all p < 0.05). Applying BFR during rest between high-intensity interval exercise sets increases physiological stresses without affecting exercise intensity or perceptual responses; applying BFR during moderate-intensity exercise may increase both physiological and perceptual responses beyond those of high-intensity exercise. Study registration: Clinicaltrials.gov (NCT05835544).