[Objective] It is well known that KAATSU resistance training can produce muscle hypertrophy without deteriorating cardiovascular system in older adults. However, it is unclear whether KAATSU resistance training exceeding 12 weeks were a highly safe and effective training method for improvement of skeletal muscle mass in older adults. We examined effect of 24 weeks of KAATSU resistance training on femoral muscle size and its safety for older adult.

[Methods] The subject was an 84-year-old woman (standing height 153 cm and body weight 46 kg). The KAATSU resistance training was provided for a total of 48 sessions over 24 weeks. Training intensity and volume were set at 20% or 30% of one-repetition maximum (1-RM) and 75 repetitions for knee extension and leg press exercises, respectively. Mid-thigh muscle cross-sectional area (CSA) was measured by MRI scan before, 12 weeks, and 24 weeks after the training. The maximal strength, chair-stand test, hemodynamic parameters, arterial stiffness, coagulation system and muscle damage were also measured.

[Results] Quadriceps muscle CSA, 1-RM strength and chair-stand test increased throughout 24-week training period. On the other hand, there were no changes in body weight, hemodynamic parameters (except for systolic blood pressure), arterial compliance coagulation system and muscle damage throughout the training period.

[Conclusion] The 24 weeks of KAATSU resistance training may be a highly safe and effective training method for improvement of skeletal muscle mass in older adults.

[Purpose] KAATSU training is a method that increases muscle activity even at low loads. In this study, we examined how different KAATSU pressure modulates elbow flexor activities during low-load elbow flexion and extension in an elderly female frail patient.

[Method] A 89-year-old female patient who had repeated hospitalization due to chronic heart failure and undergone transcatheter aortic valve implantation (TAVI) for severe aortic stenosis participated in this study. The participant performed a series of right elbow flexion and extension with a 500g weight wound around the right wrist joint and surface electromyograms (EMG) of right biceps brachii (BB) and brachioradialis (BR) were recorded. The exercises conditions were in control (without KAATSU, KAATSU 0), 120 SKU (KAATSU 120) and 150 SKU (KAATSU 150) on the proximal part of right upper limb. The number of exercises was 20 trials x 3 sets for each condition. We recorded muscle strength of maximum isometric voluntary contraction (MVC) measured with a hand-held dynamometer before the start of each condition. EMG was expressed as %MVC and averaged for flexion and extension phase in each condition. A rate of perceived exertion (RPE) after each set was measured by the Borg Scale.

[Results] There was no change in muscle strength during MVC before each condition. Compared with KAATSU 0, EMG activity of both BB and BR increased during flexion in KAATSU 120 and 150. Under KAATSU 120, BB activity increased in the first half of the flexion phase and BR activity increased throughout the flexion phase. Although RPE under KAATSU 150 was higher than KAATSU 120, both EMG activities under pressure 150 was lower than under KAATSU 120.

[Conclusion] An elderly female frail patient who had received TAVI showed that muscle activity under KAATSU 120 was the highest during low-load elbow flexion and extension exercises, while RPE was second highest. These results suggest that an appropriate KAATSU pressure will increase muscle activity during low-load exercise while minimize an increase of participant's burden.