# The Effects of Concussions on Static Postural Stability
## 4 Discussion
### Effects of Timing of Concussions on Postural Stability  
In the analyses of postural sway variables between the participants who had their last concussion in the years 2023-2018 (RECENT) and those who had their last concussion in the years 2017-2011 (OLD), the results revealed that the RECENT group had higher postural sway compared to the OLD group, indicating greater postural decrements. More specifically, the RECENT group demonstrated greater COP-X max in foam BL EC condition of CTSIB, showing greater postural sway in the anterior-posterior direction compared to the OLD group. This finding agrees with the researchers' original hypothesis that recent concussions would have a greater negative effect on postural stability compared to old concussions. This finding also agrees with the previous research that showed the persisting effects of concussions [3; 31; 32].  
As mentioned above, concussions disrupt the anatomy and physiology of vestibular and visual systems, leading to postural instability. This disruption is pronounced during the immediate three weeks after concussion and is considered to resolve by three months post-concussion [31]. However, this recovery depends on the person and multiple other factors, such as age, activity level, previous history of concussions, the severity of the concussion, co-existing neurological disorders, stress, and pre-mature return to work/play, where some individuals were shown to have lingering effects until a few years post-concussion [31]. As such, they could have postural decrements lasting from immediately after the concussion to a few years until the vestibular system returns to normal. Additionally, concussions cause post traumatic vestibular migraines, positional vertigo, and spatial disorientation, which can have a significant effect on someone's postural stability [21].  
The findings of this study have a few practical implications. Since it is evident that concussions cause postural instabilities, it would be a decisive factor when determining an athlete's return to play following a concussion. Premature return to play after a concussion is known to increase their risk of PCS and possibly fatal second impact syndrome, it is crucial to determine the appropriate time to return [33]. As the timing of full recovery is still unclear, balance and gait assessment should be a part of the concussion assessment. Moreover, since disruption of the vestibular structure and function is the major reason for the postural issues following concussions, vestibular rehabilitation therapy (VRT) could improve the recovery time [28; 29]. Additionally, it has been shown that when VRT is combined with cervical therapy, it allows the athletes to be able to return to play within eight weeks of their concussion [29].  
This study is not without limitations. Not considering the severity and timing of each concussion was a limitation, which narrowed the possibility of further assessing the effects of multiple concussions on postural stability. As the sample size of the present study was small (\(n=30;17\) had a history of concussions), the participants were not categorized according to the severity or the timing of the concussion. Thus, having a smaller sample in the CONC group could also have affected the secondary analyses (MULTIPLE vs. ONCE and RECENT vs. OLD comparisons). Hence, future studies could be focused on recruiting a larger sample with a concussion history and considering potential confounding factors, including the severity and timing of concussions and clinical interventions such as VRT in analyses. Furthermore, this study recruited young healthy adults, who are known to have a rapid and excellent recovery; geriatric and clinical populations would yield different results. Additionally, future studies could focus on investigating the timing of full recovery following concussions.