2005 Volume 1 Issue 1 Pages 13-18
Growth hormone (GH) is secreted in a pulsatile fashion during exercise, which promotes skeletal muscle growth and muscle strength. We compared the effects of different types of short-term low-intensity resistance exercise (STLIRE) on the hemodynamic and GH responses of men aged 20 to 45 years. Eleven untrained men performed 30 repetitions for 2 to 4 sets (mean 61 ± 7 repetitions) until fatigue for bilateral leg extension-flexion exercise (20% of 1 RM -Proteus Multi Exercise Machine) under the conditions of reduced muscle blood flow by applied pressure at the proximal ends of both legs by a specially-designed belt (Kaatsu Training). In the controlled exercise condition, without Kaatsu (n=9), subjects again performed the same exercise protocol as described above. Finally, a group of 5 men performed 3 sets of 10 repetitions using the Power Rehabilitation machine. Hemodynamic parameters were measured by using the impedance cardiography. Serum concentrations of GH, noradrenaline (NOR), and lactate were also measured. STLIRE with Kaatsu significantly increased GH, compared to STLIRE without Kaatsu. Maximal heart rate (HR) and blood pressure (BP) in STLIRE with Kaatsu were higher when compared to the control condition, however, stroke volume (SV) was lower compared to the controlled condition due to a decreased venous return induced by Kaatsu training. Total peripheral resistance (TPR) did not change significantly. The increase in NOR and lactate in STLIRE with Kaatsu was also significantly higher than without Kaatsu. These results suggest that “Kaatsu” leg resistance exercise caused a significant exercise-induced GH response even in STLIRE, with a reduction of cardiac preload during exercise. The results of the study indicate that Kaatsu training may become a unique method for rehabilitation in patients with cardiac diseases or low physical fitness.