Jochen Kressler, Tracie Wymer, Antoinette Domingo
Exercise and Nutritional Sciences, San Diego State University, 92182 San Diego, USA. E-mail: jkressler@mail.sdsu.edu
DOI: 10.2340/16501977-2281

Objective: To investigate the effects of overground bionic ambulation with variable assistance on cardiorespiratory and metabolic responses in persons with motor-incomplete spinal cord injury.
Design: Case series.
Subjects: Four participants with chronic, motor-incomplete spinal cord injury.
Methods: Subjects completed a maximal graded exercise test on an arm-ergometer and 3 6-min bouts of overground bionic ambulation using different modes of assistance, i. e. Maximal, Adaptive, Fixed. Cardiorespiratory (oxygen consumption) and metabolic (caloric expenditure and substrate utilization) measures were taken using a mobile metabolic cart at each overground bionic ambulation assistance.
Results: Cardiorespiratory responses ranged from low (24% VO2peak) for the least impaired and fittest individual to supramaximal (124% VO2peak) for the participant with the largest impairments and the lowest level of fitness. Different overground bionic ambulation assistive modes elicited small (3–8% VO2peak) differences in cardiorespiratory responses for 3 participants. One participant had a large (28% VO2peak) difference in cardiorespiratory responses to different modes of overground bionic ambulation. Metabolic responses mostly tracked closely with cardiorespiratory responses. Total energy expenditure ranged from 1. 39 to 7. 17 kcal/min. Fat oxidation ranged from 0. 00 to 0. 17 g/min across participants and different overground bionic ambulation modes.
Conclusion: Overground bionic ambulation with variable assistance can substantially increase cardiorespiratory and metabolic responses; however, these responses vary widely across participants and overground bionic ambulation modes.

People with Spinal Cord Injury (SCI) often have a very limited ability to walk. However, walking is one of the simplest and easiest ways to exercise important systems of your body such as the heart, the blood vessels, lungs and muscles. Since walking involves the large muscles of the leg it is also a great way to burn calories. All of this is impaired in people with SCI. Currently, there are machines called bionic exoskeletons that help people with SCI to stand up and walk. The newer versions can vary assistance so that people with SCI can contribute their own effort to walking if possible. But no one yet knows how effective these new versions are in exercising the body systems mentioned above. We studied 4 people SCI who still had some muscle function. We tested three different levels of assistance given by an exoskeleton walking machine to see how much each exercises the heart, lungs and blood vessel and the number of calories burned. For the fittest person, no matter the amount of assistance, the exercise was not very hard and did not burn a lot of calories. For the other three participants, the exercise was hard to very hard and they burned a lot more calories, but results varied depending on the participant and assistance type. Based on these findings, 3 out of the 4 people we tested could theoretically get substantial health benefits training with the exoskeleton using the right level of assistance and training strategy.