Energy cost of locomotion of robotic-assisted walking in paraplegics: a case report

Background: Mechanical orthoses are frequently withdrawn from the domestic use, due to the high energy required by walking. Purpose: This study aimed at assessing the metabolic expenditure of walking with an electrically-powered exoskeleton and to compare the energy cost of locomotion with the costs of passive or hybrid devices. Methods: Expiratory gases concentration and heart rate were measured during wheelchair- and exoskeleton-assisted locomotion, at the most comfortable- and lower-speed in a paraplegic subject (female, 28 years, lesion level L1, ASIA B). Energy cost of locomotion was calculated and compared to previously published data. Results: Oxygen consumption during exoskeleton-assisted walking at lower and comfortable speed (12.4±0.8, 15.5±0.9 ml·kg-1·min-1, respectively) were similar to the expenditure measured during wheelchair-ambulation at comfortable speed (14.5±0.7 ml·kg-1·min-1; P=ns). Walking energy cost was higher during locomotion with exoskeleton (0.69±0.05 and 0.63±0.04 ml·kg-1·m-1 for lower and comfortable speed, respectively, P<0.001 between speeds) than wheelchair-ambulation (0.15±0.01 and 0.16±0.01 ml·kg-1·m-1 for lower and comfortable speed respectively, P<0.05 between speeds) but lower than those reported in previous studies. Conclusion: Considering the findings of this case report, compared to passive and hybrid orthoses, robotic exoskeleton increases walking speed and decreases energy-cost.