The acute muscular response to two distinct blood flow restriction protocols.

The purpose of this study was to determine acute physiological and perceptual responses to two commonly implemented blood flow restriction protocols. Using a within-subject design, 15 participants (age ∼25) performed four sets of unilateral elbow flexion with each arm. One arm exercised using a 3-cm elastic cuff inflated to 160 mmHg, whereas the other arm exercised using a 5-cm nylon cuff inflated to 40% of the individual's arterial occlusion pressure. While both protocols elicited increases in acute muscle thickness [pre: 4.5 (0.2) cm, post: 5.0 (0.2) cm; p < 0.001] and electromyography amplitude [first 3 reps: 55 ( 5 ) %MVC; last 3 reps: 87 ( 10 ) %MVC], there were no differences between conditions. Both protocols produced decreases in post-exercise strength (pre: 70 Nm, post: 51 Nm; p < 0.001) with no difference between conditions. The nylon protocol resulted in more repetitions during sets 2 [13 ( 2 ) vs. 9 ( 4 ); p = 0.001] and 3 [10 ( 2 ) vs. 7 ( 4 ); p = 0.05], while producing lower levels of discomfort following each set (average 3 vs. 4; p < 0.05). In conclusion, both protocols produced similar acute responses thought to be important for promoting muscle growth. However, the use of arbitrary pressures may place some individuals under complete arterial occlusion which may increase the potential risk of an adverse event.