Muscle oxygenation and plasma growth hormone concentration during and after resistance exercise: Comparison between “KAATSU” and other types of regimen

We investigated the acute effects of “Kaatsu” resistance exercise and other types of exercise on muscle oxygenation and plasma growth hormone. Six young male bodybuilders performed leg extension exercise according to four exercise regimens: low-intensity ∼30% of one repetition maximum (1RM) exercise with moderate occlusion (LO-Kaatsu), low-intensity (∼50% 1RM) exercise with slow movement and tonic force generation (3 s for lowering and 3 s for lifting actions, 1-s pause, and no relaxing phase; LST), low-intensity (same as LST) isometric exercise at 45° knee angle (ISO), and high-intensity (∼80% 1RM) exercise with normal movement speed (HN), commonly used for gaining muscular size and strength. The muscle oxygenation level measured with near-infrared continuous-wave spectroscopy (NIRcws) showed the largest changes during and after LO-Kaatsu among all regimens. The minimum oxygenation level during LO-Kaatsu was the lowest among the four exercise regimens. On the other hand, the increases in muscle oxygenation after LO-Kaatsu were the largest among the four regimens. Plasma GH and blood lactate concentrations after LO-Kaatsu, LST and HN were significantly (P < 0.05) higher than those after ISO, but there were no significant differences among those after LO-Kaatsu, LST and HN. The results indicate that “Kaatsu” resistance exercise causes marked changes in muscle oxygenation level and circulating growth hormone, both of which may be related to muscular hypertrophy.