## 4 Discussion
In addition, the significant decrease found for the heel-S2-occipt (HSO), heel-S2-nasion (HSN), and heel-S2-C7 (HSC) anterior whole-body angles underlined the significant anterior position, respectively, of the occupt, nasion and C7 with respect to the sacrum and to the heel (Table 2; Figure 4a). These findings regarding the sagittal alignment of the whole body confirmed the anteriorization of the head-cervical region with respect to the sacral region and to the feet in PD patients compared to healthy controls (Figure 4a), whereas only a trend of increased trunk tilt and decreased dorsal angle were found. Therefore, in this sample of patients, the abnormality of the cervical-head region is more relevant with respect to trunk one (hyper-kyphesis or trunk tilt). As far as the PD group was concerned, significant short- and long-term improvements were observed after wearing the K1 Posture Keeper. This effect was quantified through whole-body assessment of the sagittal posture during standing and walking via 3D motion analysis. Indeed, in upright standing, the results showed a significant increase in SCO angle in the measure acquired at T1 when wearing the orthosis with respect to baseline condition (T0 without wearing K1) (Table 3; Figures 4b and 5b). In particular, this improvement was observed for the head-cervical region with a significant decrease in CNA in T1 with the K1 condition with respect to T0 without K1 (Table 3 and Figure 5a), underlining a decrease in antecollis in upright standing (Figure 4b). These results showed that wearing the K1 Posture Keeper could lead to long-term sagittal improvements during upright posture in PD population, inducing a posteriori of the cervical-head region compared with the T0 condition, with a trend of normalization of the occupt and nasion values with respect to the C7 and sacrum ones, as represented in Figure 4b. Furthermore, the evaluation of whole-body posture during walking confirmed the therapeutic role of the K1 Posture Keeper in PD patients. In fact, the results reported in Table 4 showed a significant increase in SCO average in all conditions with respect to T0 without K1, and a significant decrease in CNA average in T1 with and without K1 compared to T0 without K1 (Figure 6a,b), suggesting a reduction in the antecollis during walking. Moreover, a significant increase in HSN average in T0 with K1 and in T1 without K1 compared to T0 without K1 (Table 4 and Figure 6c) confirmed the back shift of the nasion with a better alignment of the head with respect to the trunk, pelvis, and feet, underlining an improvement in the sagittal alignment of the entire body in PD patients during walking (Figure 4b). Additionally, a significant decrease in the excursion range values of CNA and DA found in T1 compared to T0 (Table 4) could suggest a greater postural stability of PD patients during walking due to a reduction in oscillations on the sagittal plane thanks to the long-term effect of the K1 Posture Keeper. These results are in line with a previous work by [PERSON] [29], reporting an improvement in static and dynamic balance while wearing a posture shirt, also suggesting a possible therapeutic role in reducing the risk of falls  
Other previous evidence includes that from [PERSON] and colleagues, reporting an improvement in the forward bend posture and gait parameters while wearing a spinal kyphorothosis [32]. [PERSON] et al. also reported an improvement in neck flexion in people with PD using a neck corset combined with lidocaine injection [30]. However, no previous studies have reported the long-term effect of orthoses on postural alterations in PD. We could speculate that a reorganization of the proprioceptive/sensory system following the wearing of the corset could be at the basis of our findings. Indeed, altered proprioception is described in people with PD, particularly with axial abnormalities [48]. It was proposed that proprioceptive dysregulation could contribute to camptocormia development.