Exoskeleton assist devices support body movements by containing the lower limbs within a rigid scaffold with motorized joints to support and assist limb movement during physical efforts. Modern exoskeleton systems are able to provide reactive support, only engaging mechanical joints to assist movement (i.e., active movement) rather than initiate joint movements (i.e., passive movement). Exoskeleton systems can be used to assist over-ground walking in individuals with preserved locomotor function or can be paired with treadmill or BWSTT systems to partially support body weight to accommodate non-weight bearing individuals. The available evidence supporting exoskeleton devices for improvement in cardiorespiratory fitness comes from a combination of over-ground and over-treadmill walking, summarized below.
The general observations from the available exercise training studies indicate that exoskeleton-assisted exercise training primarily improves exercise capacity in exoskeleton-specific movements and its improvements do not largely translate to central cardiovascular fitness as determined by conventional arm cycling tests. Five studies employed over-treadmill exoskeleton-assisted walking, and one study used over-ground exoskeleton-assisted walking. By nature of the intervention, all participants engaged in active walking (i.e., the exercise was not passively guided).
In a case series, Gorgey, Wade et al. (2017) indicated that over-ground exoskeleton training was feasible in a small group of individuals undergoing a clinical rehabilitation program, providing support that mode-specific exercise capacity can improve with only one hour of exoskeleton training per week for greater than 10 weeks.
There is Level 1 evidence (Gorman et al. 2019; Gorman et al. 2016) that 3 months of exoskeleton exercise training can improve exoskeleton-specific exercise capacity.
There is Level 4 evidence (Gorgey, Wade et al. 2017) that 10 weeks of exoskeleton exercise training can increase exoskeleton walking time and walking duration.
There is Level 4 evidence (Hoekstra et al. 2013) that 10 weeks of exoskeleton exercise training can increase submaximal heart rate and lower resting heart rate.