# Comparison of Gait Smoothness Metrics in Healthy Elderly and Young People
## 4 Discussion
### Walking Condition Comparisons  
To our knowledge, there is no existing literature that has conducted a comparison of smoothness within the same healthy subject groups concerning normal self-selected speed versus fast self-selected speed. Regarding the older subjects in our study, the analysis revealed that LDLJ metrics indicated a smoother gait during the fast-walking task compared to the normal pace. Notably, these results showed significance in statistical terms across the metrics derived from both accelerations and angular velocities. Conversely, when assessing smoothness using LDLJ in the two distinct gait tasks among the younger group, the findings indicate a smoother gait during the normal walking pace compared to the faster walking task.  
Similarly, analogous observations arise from the SPARC smoothness calculations for both the younger and older individuals. However, when considering the older group, it is noteworthy that statistical differences were observed solely in the angular velocities.  
In the older group, HR-based smoothness analysis revealed statistical differences exclusively for acceleration along ML and AP directions, as well as for all angular velocity calculations except in the AP direction. Interestingly, contrary to the observations made using SPARC and LDLJ, the analysis indicates that the normal walking task is smoother than the fast-paced task. Conversely, in the analysis of the younger group, HR highlighted that the normal gait is smoother than the faster pace with statistical differences across all examined variables. In both group analyses, HR's observations stand in stark contrast to SPARC and LDLJ trends.  
The divergence in smoothness between normal and fast gaits in young individuals could be attributed to the significant change in absolute speed when transitioning from normal to fast walking. Some previous studies have indicated that self-selected normal walking velocity tends to be the smoothest compared to slower and faster paces [3; 31]. In this study, both LDLJ and SPARC metrics corroborated the trends observed in prior research, supporting the notion that normal gait exhibits greater smoothness. However, HR presented an opposing viewpoint, which was the metric adopted in these two studies to calculate smoothness. On the other hand, older individuals maintained a comparable velocity during the fast gait, similar to that of the normal task. Consequently, despite some statistical differences observed, the smoothness variations between the two tasks in older individuals could be deemed negligible.  
However, determining a singular methodology as a reliable standard for smoothness estimation remains still inconclusive. Investigation involving different metrics is essential to establish consistency in the obtained results.  
It is crucial to acknowledge the limitations inherent in our study. The first limitation relates to the relatively short distance covered in the gait analysis. The brevity of the walking path may have implications for the generalizability of our findings, and future studies should consider longer walking distances. Furthermore, our study lacked a comparison with individuals affected by neurological disorders or cognitive impairments. Including individuals with specific pathologies in future research could provide a more robust framework for assessing age-related changes in gait smoothness. Another interesting future investigation can be the implementation of the TUG test in our methodology. The TUG test could offer valuable insights into dynamic balance and overall gait performance, complementing our current findings.