Walk training combined with blood flow restriction (BFR) leads to hypertrophic effects in leg muscle, but the underlying physiological mechanisms are poorly understood. We examined the time course of the acute effects of BFR slow walk (BFR-slow; walking speed 56 m/min), BFR fast walk (BFR-fast; walking speed 87 m/min), and control walk (CON-slow; walking speed 56 m/min) on ultrasound-measured muscle thickness (MTH) and on isometric knee extension strength in 8 young men. No differences in baseline MTH and isometric strength were observed between the sessions. MTH of the quadriceps and triceps surae increased (p < 0.05) during and immediately after the BFR-slow (8 to 11% and 2 to 4%, respectively) and BFR-fast (7 to 8% and 3 to 5%, respectively) sessions, but not in the CON-slow (-2% and 0%, respectively) session. There were no significant differences in quadriceps and triceps surae MTH between the BFR-slow and the BFR-fast sessions. No changes in MTH were observed for the lumbar multifidus following each walking session. Isometric strength was unchanged during and immediately after the BFR-slow, BFR-fast, and CON-slow sessions. Our results indicated that acute increases in muscle size occurs following walk exercise combined with leg blood flow restriction regardless of gait speed which may influence BFR-walk induced muscle hypertrophy.
Key words: Vascular occlusion, ultrasonography, muscle size, maximum voluntary contraction.
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