Generally, a threshold intensity of 65% 1-RM will induce muscle hypertrophy; however, recent studies using low-intensity (20% 1-RM) exercise combined with vascular restriction (KAATSU) have demonstrated increases in muscle size and strength. PURPOSE: To investigate the EMG and MMG responses, and percent voluntary activation (PVA) of the vastus lateralis (VL) following exposure to low-intensity intermittent isometric exercise in combination with moderate vascular restriction.METHODS: Twelve males (Age = 23.7 ± 4.1 yrs) participated in 1 familiarization trial and 2 experimental trials (with or without KAATSU) each separated by 48 h. Testing order was: a) Resting blood pressure after 5 min rest; b) 5 min warm-up on a cycle ergometer (50 W, 50-70 rpm); c) 2 preexercise 5-s isometric MVCs, 1 min rest between trials; d) 5 sets of 20 intermittent isometric contractions (2-s on / 1-s off) at 20% of MVC, 30-s interset rest periods; and e) 2 post-exercise isometric 5-s MVCs. RESULTS: There were no significant interactions or main effects for time or session for pre- and post-exercise isometric MVCs, with and without KAATSU, for the following parameters: MVC, PVA, EMG amplitude, EMG mean power frequency (MPF), MMG amplitude, and MMG MPF. Average normalized EMG amplitude increased significantly from repetitions 1-4 to 5-8 to 9-12 and MMG amplitude increased significantly from set 1 to 2 for both the KAATSU and no-KAATSU sessions. CONCLUSION: Intermittent isometric contractions at 20% 1-RM, with or without vascular restriction, are not intense enough to cause significant muscular fatigue.

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Dynamic exercise induces changes in the redistribution of whole-body organ-tissue blood circulation, including cutaneous blood circulation. We hypothesized that limb exercise combined with the restriction of muscular blood flow (KAATSU) may influence cutaneous blood flow redistribution. To examine this hypothesis, forehead (supraorbital) cutaneous blood flow was compared in women performing exercises with and without KAATSU. Ten young and middle-aged female subjects in the supine position performed three sets of 15 repetitions of unloaded unilateral knee extension exercises (30-s rest between sets). Blood flow was calculated from blood velocity and red blood cell mass (blood flow = velocity ^* mass) determined by laser blood flowmetry. While exercise without KAATSU did not induce alterations in velocity and mass (hence, no alterations in blood flow) throughout the entire exercise series, exercise with KAATSU induced increases (P<0.05) in blood flow owing to increases in velocity. These increases were not eliminated during the rest periods between exercise sets. Heart rate (HR) increased (P<0.05) with the second and third sets of exercises with KAATSU compared with HR before exercise initiation, and was higher than the HR resulting from a corresponding set of exercises without KAATSU. There were no changes in blood lactate and hematocrit in both types of exercises. Norepinephrine increased (P<0.05) at the completion of the exercise sets. These results suggest that forehead cutaneous blood circulation was increased by unloaded KAATSU leg exercise.

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The purpose of this study is to develop a unique method to enhance autonomic nervous system (ANS) activity by means of experimental leg occlusion. The effects of blood flow restriction on the activities of the ANS during rest were investigated using a power spectral analysis of heart rate variability. Two patterns of occlusion were randomly assigned to healthy subjects: pattern A, 10 min of 1.4 times of systolic blood pressure; pattern B, 5 min of mean blood pressure followed by 5 min of 1.4 times of systolic blood pressure. Electrocardiogram, blood pressure and cardiac output were continuously monitored during rest and occlusion. During occlusion, cardiac output and stroke volume showed significant decreases, due to modulation of autonomic nervous activity. After releasing from occlusion without blood pooling (A), the high frequency component of R-R interval variability representing vagal activity showed a significant increase (P<0.05). However, soon after releasing, the ECG QTc interval temporally prolonged (P<0.05) and recovered gradually. Further investigation is recommended to determine blood flow occlusion safety on the cardiac depolarization-repolarization process. In conclusion, the results suggest that blood flow restriction has potential to be a useful method to stimulate the activity of autonomic nervous system, and especially to enhance parasympathetic nervous system activity.

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The application of an orthostatic stress such as lower body negative pressure (LBNP) during exercise has been proposed to minimize the effects of weightlessness on the cardiovascular system and subsequently to reduce the cardiovascular deconditioning. The KAATSU training is a novel method for strength training to induce muscle strength and hypertrophy. KAATSU induces venous pooling of blood in capacitance vessels by restricting venous blood flow. Therefore, to investigate whether KAATSU can be used as an orthostatic stress, we examined the effects of KAATSU on the hemodynamic, autonomic nervous and hormonal parameters in one subject. The several parameters were measured by impedance cardiography; heart rate (HR), mean blood pressure (mBP), stroke volume (SV), cardiac output (CO), total peripheral resistance (TPR), and heart rate variability (HRV). These data were obtained before (pre), during and after (post) pressurization (50 and 200 mmHg) on both thighs with KAATSU mini belts, and compared with those in standing. The serum concentration of noradrenaline (NA) and vasopressin (ADH), and plasma rennin activity (PRA) were also measured. The application of 200 mmHg KAATSU decreased SV, which was almost equal to the value in standing. HR and TPR increased in a similar manner as standing with slight change of mBP. High frequency (HF_RR), a marker of parasympathetic nervous activity, decreased during both 200 mmHg KAATSU and standing, while LF_RR/HF_RR, a quantitative marker of sympathetic nervous activity, increased significantly. During KAATSU and standing, NA, PRA and ADH increased. These results indicate that the application of KAATSU on both thighs simulates systemic cardiovascular effects of orthostasis in one gravity (1G), and that KAATSU training appears to be a useful method for potential countermeasure like lower body negative pressure (LBNP) against orthostatic intolerance in space flight as well as strength training to induce muscle strength and hypertrophy.

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The effectiveness of KAATSU resistance training (Kaatsu) has been established as a method not only to increase muscle size and power but also to benefit patients with orthopedic and cardiac diseases. The method is a low-intensity resistance exercise (20∼30% of one repetition maximum, 1RM) with a restriction of the venous return using a specially designed pressurized cuff or belt at the proximal end of the upper or lower extremities. The increases of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) by Kaatsu resistance training are considered to play an important role in elucidating the mechanism of Kaatsu. In this case, the sinus pause of a patient with sick sinus syndrome (SSS) decreased to approximately 40% with Holter ECG monitoring after Kaatsu resistance training. The mechanism regarding such an improvement by Kaatsu is herein discussed. Therefore, an additional effect of Kaatsu is reported concerning the decreased sinus pause observed in a SSS patient.

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