Several exoskeletons have been developed and increasingly used in clinical settings for training and assisting locomotion. These devices allow people with severe motor deficits to regain mobility and sustain intense and repetitive gait training. However, three factors might affect normal muscle activations during walking: the assistive forces that are provided during walking, the crutches or walker that are always used in combination with the device, and the mechanical structure of the device itself. To investigate these effects, we evaluated eight healthy volunteers walking with the Ekso, which is a battery-powered, wearable exoskeleton. They walked supported by either crutches or a walker under five different assistance modalities: bilateral maximum assistance, no assistance, bilateral adaptive assistance, and unilateral adaptive assistance on each leg. Participants also walked overground without the exoskeleton. Surface electromyography was recorded bilaterally, and the statistical parametric mapping approach and muscle synergies analysis were used to investigate differences in muscular activity across different walking conditions. The lower limb muscle activations while walking with the Ekso were not influenced by the use of crutches or walker aids. Compared to normal walking without robotic assistance, the Ekso reduced the amplitude of activation for the distal lower limb muscles while changing the timing for the others. This depended mainly on the structure of the device, and not on the type or level of assistance. In fact, the presence of assistance did not change the timing of the muscle activations, but instead mainly had the effect of increasing the level of activation of the proximal lower limb muscles. Surprisingly, we found no significant changes in the adaptive control with respect to a maximal fixed assistance that did not account for subjects’ performance. These are important effects to take into careful considerations in clinics where these devices are used for gait rehabilitation in people with neurological diseases.

Purpose With an increase in the number of adapted sports, the need to monitor sports performance in people with different abilities has grown. Indeed, a thorough evaluation of the sports gesture could prevent the occurrence of injuries, enable a continuous performance assessment, and allow to verify the compliance of the requirements for the competitions. Gesture kinematics provides an assessment of performance, while the muscle activities reveal the underlying strategies adopted by each athlete. In this context, we propose an instrumented evaluation to assess performance in Para-powerlifting. Our goal is to define and test a setup and a protocol to quantitatively assess the execution of bench press exercise in athletes with different abilities. Methods We recruited an unimpaired athlete and three Paralympic athletes. They were requested to execute the bench press exercise while we recorded muscle activity and kinematic data from the upper body. We investigated the sport gesture by extracting parameters describing coordination, symmetry, and synchronism between arms, and motor variability while repeating the gesture. Results Paralympic athletes performed the gestures with higher coordination between arms and low variability across repetitions compared to the unimpaired athlete, who was not at the Olympic level. All participants obtained similar kinematic performance by adopting different muscle strategies. Conclusions This study is a proof of concept that the instrumented evaluation proposed here can allow to conduct a complete assessment of the bench press exercise, in terms of kinematics, muscle activity and performance in athletes with different abilities.

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