Ultrasound analysis of acute muscle swelling and discomfort following low-load BFR and high-load resistance exercise in upper and lower limbs

Few studies compare acute muscle swelling between upper and lower limbs with blood flow restriction (BFR), and lower pressures may reduce the often-reported discomfort. The purpose was to examine differences in acute muscle swelling, discomfort, and exercise preference between low-load BFR and high-load resistance exercise in upper and lower limbs. Sixty-one participants (25.7 ± 7.9 years; 32 males, 29 females) completed four exercise conditions: upper limbs (UL) randomized to low-load BFR (BFR-UL) or high load (HL-UL), then lower limbs (LL) randomized to low-load BFR (BFR-LL) or HL (HL-LL). BFR-LL was performed at 30% 1RM with four sets to failure at 50 mmHg cuff pressure; HL exercises were at 70% 1RM with four sets of 8–12 reps. Swelling, discomfort (0–10 scale), and exercise preference were assessed. Results were presented as mean [SD]. The most probable predictor of swelling was identified in limbs (posterior inclusion probability = 0.996; BF10 = 846.447; BFincl = 156.329), with strong evidence against a condition × limb interaction for swelling (BFincl = 0.178). Swelling had a greater increase in lower limbs compared with the upper limbs (BF10 = 946.447; BFincl = 158.344), while evidence for condition effects was anecdotal (BFincl = 0.206). There was strong evidence against a set × limb × condition interaction for discomfort (BF10 = 0.083), with no preference for upper limb condition (BF10: 0.236), and anecdotal preferences for the lower limbs (BF10 = 0.626). Acute muscle swelling and discomfort did not differ across conditions, supporting low-load, low-pressure BFR as a practical alternative to high-load training.