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, VO2max 47.0 ± 5.5ml∙kg∙min-1) completed four experimental conditions in a randomised crossover manner: (i) high-intensity control (HI) – 100% maximal aerobic power (Wmax); (ii) high-intensity recovery occlusion (HIRO) – 100%Wmax, 80% limb occlusion pressure (LOP) during rest; (iii) moderate-intensity low occlusion (MILO) – 70%Wmax, 50%LOP during exercise; and (iv) moderate-intensity high occlusion (MIHO) – 70%Wmax, 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 textless 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 textless 0.05). Higher vastus lateralis muscle activity was exhibited on the last exercise repetition of HIRO than HI (p textless 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 textless 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.