# Development and Preliminary Evaluation of a Lower Body Exosuit to Support Ankle Dorsiflexion
## 5 Discussion
### Influence on Gait Kinematics and Muscle Activity  
The purpose of the preliminary evaluation was to identify any restriction in the degrees of freedom for the ankle while walking with the exosuit in comparison to a non-assisted healthy gait. Moreover, a possible reduction in muscle activation by using the exosuit should be analyzed. We hypothesized that there are no restrictions at the ankle kinematics due to the soft structure of the exosuit and the high dynamics of the pneumatic actuation. The results show that the angle curves of the ankle in all three planes and of the knee and hip joint in the sagittal plane do not differ from a healthy gait when walking with the assistance of the exosuit. The null hypothesis was therefore not rejected, as hypothesized. Because of the retention of the analyzed gait kinematics, the exosuit could be suitable for use by patients with dorsiflexion weakness without restraining plantar flexion or introducing negative effects on gait and joint kinetics like passive orthosis does [14]. Hence, the exosuit may be an appropriate solution for gait training with neurological impairment. For rehabilitation of patients suffering from drop foot, optimized training enhancing the unhealthy gait characteristics including compensation mechanisms such as hip hiking and circumduction is targeted. Since it is a neuromuscular disease, the goal of the corresponding training is to stimulate an afferent input regarding a healthy gait pattern, which in turn could activate efferent motor pathways and thereby retrain the addressed muscles in a positive manner [51; 52; 53]. Moreover, activating and using the weakened muscles counteracts muscle atrophy. As it is highly relevant for patients to train and activate dorsiflexion muscles, a reduction in muscle activity while using any assistive device would be counterproductive. The risk of \"passive movements\" and therefore reduced muscle activity could not be seen while walking with the current exosuit. There was no significant difference in muscle activation of the dorsiflexion muscle tibialis anterior during the walk. Hence, the provided support during the concentric activation phase of m. tibialis anterior seems not to lead to a different motor adaption, which is in accordance with the results of other actively powered ankle devices [54]. The current developed exosuit might have the potential to improve rehabilitation training on the one hand and facilitate walking in the daily routine on the other hand. As a result, an independent and self-reliant gait with a lower risk of a drop foot-related stumbling and falling is aspired to. Therefore, the next step for evaluating the exosuit is to have patients with drop foot test it. Besides the increase in the toe clearance at swing phase, spatiotemporal parameters such as step length and step width, as well as their symmetry between left and right leg, should also be taken into account. Methodically, SPM1d is preferable for evaluating the effects of assistive devices to one-dimensional biomechanical data such as kinematics, kinetics and EMG. Regarding a holistic approach, SPM allows us to examine the whole time-series data without focusing on special discrete parameters such as maximum or minimum values, which would disregard important information. The used method is able to ensure the current subgoal of the iterative development and was necessary before proceeding to the next step of evaluation. Nevertheless, there are some limitations regarding the current study. The familiarization period of five minutes seems to be too short, due to the noticeable greater variance during the exosuit walking condition. Especially regarding a following analysis of patients, they should have more time to discover the assistive device for achieving a steady state while walking with the system. Furthermore, joints of the contralateral leg should be taken into account when interpreting the effect of an exosuit by doing a gait analysis. This also requires a larger number of subjects.