Effects of a lumbar-type hybrid assistive limb on cardiopulmonary burden during squat exercise in healthy subjects

The lumbar-type Hybrid Assistive Limb (HAL) is expected to expand the possibilities of exercise therapy for severe cardiac patients who have difficulty in moving on their own legs. We investigated whether motion assistance from HAL during squat exercise could effectively reduce the cardiopulmonary burden in healthy subjects. Twelve healthy subjects (33 ± 11 years) performed squat exercise for 3 consecutive minutes at a repetition rate of 20 squats per minute with and without assistance from a lumbar-type HAL. The oxygen uptake (VO2), carbon dioxide output (VCO2), minute ventilation (VE), and the Borg Scale were monitored during exercise. VO2 (930 ± 207 vs 992 ± 169 mL/min, p < 0.05) and the Borg Scale rating (12.8 ± 1.1 vs 13.7 ± 0.8, p < 0.05) at the end of exercise were significantly lower when HAL was used. When 2 subjects who regularly perform high-intensity exercise for more than 10 h per week were excluded from the analyses, VO2, VCO2, VE, and the Borg Scale were significantly lower when HAL was used. Our results demonstrate that the lumbar-type HAL significantly reduces cardiopulmonary burden during squat exercise in healthy subjects. The effects were especially striking in sedentary subjects. Further studies on cardiac patients are expected to establish a new cardiac rehabilitation program using HAL.

Effects of a cyborg-type robot suit HAL on cardiopulmonary burden during exercise in normal subjects

BACKGROUND

The hybrid assistive limb (HAL) is the world's first cyborg-type robot suit that provides motion assistance to physically challenged patients. HAL is expected to expand the possibilities of exercise therapy for severe cardiac patients who have difficulty in moving on their own legs. As a first step, we examined whether or not the motion assistance provided by HAL during exercise could effectively reduce the cardiopulmonary burden in healthy subjects.

METHODS

A total of ten healthy male adults (35 ± 12 years) underwent cardiopulmonary exercise testing (CPX) on a cycle ergometer with or without assistance from HAL. The CPX protocol consisted of four 3-min stages performed in a continuous sequence: rest, 0 W, 40 W, and 80 W. The heart rate (HR), blood pressure, oxygen uptake (VO₂), minute ventilation (VE), and gas exchange ratio (R) were monitored during the CPX.

RESULTS

At 0 W, the HR, VO₂, and VE were significantly higher when HAL was used. At 80 W, however, the HR (107 ± 14 vs 114 ± 14 beats/min, p < 0.01), systolic blood pressure (141 ± 15 vs 155 ± 20 mmHg, p < 0.01), VO₂ (17.6 ± 2.4 vs 19.0 ± 2.5 mL/min/kg, p < 0.05), and R (0.88 ± 0.04 vs 0.95 ± 0.09, p < 0.05) were significantly lower when HAL was used.

CONCLUSIONS

HAL has the potential to reduce cardiopulmonary burden during moderate-intensity exercise and can, therefore, be used as a support for exercise therapy. Further studies on cardiac patients are expected to contribute to the establishment of a new exercise therapy program using HAL.