## 4 Discussion  
The aim of this pilot study was to investigate the feasibility of using an elastic textile suit equipped with two passive exospines, one more and one less flexible, in terms of effects on trunk kinematics, center of mass behavior, and mechanical energy expenditure and recovery during walking. We found that CoM displacement reduced when using the exospine, compared to walking without the device, regardless of the flexibility of the exoskeleton. Moreover, we found that trunk RoMs in the frontal and transverse planes reduced in swCA when using the less flexible exoskeleton. Reducing body sway and trunk oscillations is an important rehabilitation target in swCA [26, 27], and our results are consistent with the findings by [PERSON] et al., who found a reduction of medio-lateral body sway and pelvic oscillations when swCA [14] wore a dynamic movement orthosis. Moreover, we found that the WLFE condition reduced the variability of trunk rotation. However, our sample was too small to reach consistent results in terms of correlations between the improvements in trunk range of motion and CoM displacement; therefore, this mechanism deserves to be better investigated on larger samples, particularly when wearing the less flexible configuration. We also found that _R-Step_ increased and TEC was reduced when swCA wore the less flexible exoskeleton. _R-Step_ measures the efficiency in recovering mechanical energy during the gait cycle, whereas TEC is a measure of mechanical energy consumption [45, 46]. Figure 8: For the patients without the exoskeleton (WOE), with the more (WMFE) and less flexible (WLFE) exoskeleton, and for the control (C) group, the means (\(\pm\)SD) of the full width at half maximum (\(FWHM_{\text{Trunk}}\)) and intrasubject coefficient of multiple correlation (\(CMC_{\text{Trunk}}\)) for trunk were reported. * Statistically significant differences. Figure 9: For the patients without the exoskeleton (WOE), with the more (WMFE) and less flexible (WLFE) exoskeleton, and for the control (C) group, the means (\(\pm\)SD) of the full width at half maximum (\(FWHM_{\text{Lower limb}}\)) and intrasubject coefficient of multiple correlation (\(CMC_{\text{Lower limb}}\)) for the lower limbs were reported. * Statistically significant differences. Our findings are consistent with the operating principle of the exoskeleton, which is based on the ability to store energy during the load acceptance phase and return it during the propulsion phase, allowing the patient exoskeleton system to store and reuse kinetic energy more efficiently. This is further confirmed by the results of sEMG analysis, showing a reduction in _FWHM_ and increase in _CMC_ values for both the lower limb and trunk muscles when wearing the less flexible exoskeleton. SwCA have been described to increase muscle coactivation as a global compensatory mechanism to deal with the enlarged lateral body sway caused by a lack of inter-joint coordination and hypotonia, which impairs their ability to recover energy while walking. In this way, it is possible to argue that using the less flexible exoskeleton, by allowing a more efficient walking behavior and reducing CoM displacement, reduces the need for swCA to increase the muscle coactivation and allows a better coordination between muscle activations, as expressed by _CMC_ values. This increased capacity for mechanical energy management may explain the improved behavior in the sagittal plane with the consequent reduction of spurious oscillations on the frontal plane. With each step cycle with the exoskeleton, a higher part of the CoM kinetic energy is converted into gravitational potential energy and then back into kinetic energy. In this case, the locomotory muscles must supply a lower power to overcome the losses occurring during the energy transduction required to move the CoM [45]. This is further confirmed by the results of sEMG analysis, showing a reduction in _FWHM_ and an increase in _CMC_ values for both the lower limb and trunk muscles when wearing the less flexible exoskeleton.