Traditional high-intensity resistance training performed 2-3 times per week induces muscle hypertrophy, at least, in 5 weeks (i.e. 10-15 training sessions). To examine the effect of a higher training frequency (12 sessions in 6 days), healthy young men performed low-intensity resistance training with (n=8, LIT-BFR) and without (n=8, LIT-CON) leg blood flow restriction with cuff inflation (BFR) twice per day for 6 days. Training involved 4 sets of knee extension exercise (75 total contractions) at 20% 1-RM. Significant muscle hypertrophy was observed only in the LIT-BFR group as estimated muscle-bone cross-sectional area (CSA) (2.4%), MRI-measured mid-thigh quadriceps muscle CSA (3.5%) and quadriceps muscle volume (3.0%) increased. The resulting hypertrophic potential (% change in muscle size divided by number of training sessions; ∼0.3% per session) is similar to previously reported traditional high-intensity training (0.1 to 0.5% per session). Improved 1-RM knee extension strength (6.7%) following LIT-BFR training was accounted for by increased muscle mass as relative strength (1-RM/CSA) did not change. There was no apparent muscle damage associated with the exercise training as blood levels of creatine kinase, myoglobin, and interleukin-6 remained unchanged throughout the training period in both training groups. A single bout of training exercise with and without BFR produced no signs of blood clotting as plasma thrombin-antithrombin complex, prothrombin fragment 1,2 and D-dimer were unchanged. In conclusion, changes in muscle mass and strength following 6-day (12 sessions) of low-intensity resistance training requires BFR to produce responses comparable to the effect of several weeks of high-intensity resistance training.

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The application of a gravity-specific stress (e.g. LBNP), in combination with exercise, prevents cardiovascular deconditioning in space flight. KAATSU training is a method to induce blood pooling in capacitance vessels by restricting venous return (as with LBNP) and which when combined with low-intensity resistance (RE) exercise produces remarkable muscle mass and muscle strength gains. The purpose of this study was to investigate the hemodynamic and neurohumonal responses induced by KAATSU in combination with leg RE (30 % 1 RM), during simulated weightlessness (6°head-down tilt for 24 h, n=7). Following 24 h bed rest 6° head-down tilt, body mass was decreased from 75.3 ± 3.9 to 73.3 ± 3.8 Kg (P<0.01). Blood volume (BV) and plasma volume (PV) were reduced by −4.4 ± 1.4% and −7.9 ± 2.5%, respectively. During RE, BV and PV were significantly decreased; the changes with KAATSU induced a lower-body venous pooling, resulting in a sustained decrease in stroke volume (SV; from 77.0 ± 4.4 ml to 55.9 ± 5.1 ml; P<0.01) that was comparable to resting SV while standing. Consequently, RE heart rate (HR) was greater with KAATSU. The serum concentrations of plasma renin activity (PRA), vasopressin (ADH), noradrenaline (NOR), and lactate were also significantly elevated during RE with KAATSU as compared to control RE. These hemodynamic and neurohumoral responses following head-down tilt and during RE closely approximate the gravity-specific stress observed with LBNP. Thus, when used in combination with RE, KAATSU may be a useful countermeasure in microgravity.

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The purpose of the present study was to examine the blood pressure and heart rate response to walking with and without blood flow restriction (KAATSU-walk) in the elderly. Seven active subjects (2 men, 5 women) aged between 64 to 78 years (mean age, 68.9 ± 6.3 years) performed walking test without (Control) and with KAATSU (cuff pressure 160 mmHg and 200 mmHg) on separate days. The exercise consisted of level walking at 67 m/min (4 km/hr) for 20 min. Systolic (SBP) and diastolic (DBP) blood pressure was recorded using an automatic blood pressure monitor, and mean arterial pressure (MAP) was calculated [MAP = DBP + (SBP - DBP)/3]. Heart rate (HR) and ratings of perceived exertion (RPE) were also recorded during the test. There were no significant differences (P>0.05) in blood pressure responses between the Control and KAATSU-160mmHg exercise, however significantly higher blood pressures were observed for the KAATSU-200mmHg exercise (112-127mmHg for MAP) compared to the Control. However, these values are still lower than those of previous reported during moderate to heavy resistance exercise. The correlations between HR and MAP during each exercise condition were all statistically significant (range from r=0.83 to r=0.94; p<0.05). However, the intercept of the curve was highest in KAATSU-200mmHg exercise (i.e. MAP response to the same HR was higher), suggesting the increased total peripheral resistance with high occlusive pressure. In conclusion, our results indicate that during slow walk exercise with KAATSU, level of occlusive pressure can significantly impact upon the HR and MAP responses in the elderly, These findings are consistent with the idea that the occlusive pressure by itself can significantly modulate the cardiovascular response during low-intensity KAATSU-walk.

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