Circuit training without external load induces hypertrophy in lower-limb muscles when combined with moderate venous occlusion

Abstract

The present study investigated whether circuit training with body weight alone (no external load) can cause muscular hypertrophy when combined with moderate venous occlusion (‘Kaatsu Training’). Healthy women (mean age, 32.7 ± 4.0 yr; n=22) were randomly assigned into the occlusive training group (OCC, n=11) and the normal training group (NOR, n=11). Both groups performed the same circuit-training regimen consisting of six, successive exercises for muscles in the upper and lower limbs and the trunk, at a frequency of 3 sessions/wk. Each session lasted for 5-10 min. In OCC group, proximal ends of the upper and lower limbs of both sides were moderately compressed by means of ‘KAATS Sportswear’, to restrict the venous blood flow during the exercises (preset pressure, 50-80 mmHg and 80-120 mmHg for upper and lower limbs, respectively). Cross-sectional area (CSA) of the thigh muscle was measured with spiral computer tomography. After an 8-wk period of training, the muscle CSA of both right and left limbs showed significant increases by ∼3% (P<0.05) in the OCC group, whereas there was no change for the NOR group. To propose a mechanism for these findings, the acute effects of the same exercise regimen combined with occlusion on plasma concentration of growth hormone (GH) were further investigated with male subjects (n=2). The circuit exercise with occlusion elicited a dramatic increase in plasma GH, whereas that without occlusion did not, although statistical analysis could not be made. The results indicate that circuit training with only body weight can cause hypertrophy in lower-limb muscles when combined with moderate venous occlusion, but the exact mechanism is not yet understood.