# Impact of Differing Instability Devices on Postural
## 4 Discussion
Cross-sectional examinations such as the current and previously mentioned investigation display no differences in foam-based instability devices and conclude that foam pads can be used interchangeably. A potentially more clinically relevant investigation would examine longitudinal training outcomes using the different devices both independently and as a part of a systematic progression. Previous investigations examining the effect of unilateral balance training interventions have used built-in systematic progressions, such as the inclusion of additional motor/cognitive tasks to make the training more complex. It would be of interest to explore whether adding additional cognitive and/or motor tasks would impact the longitudinal results using the devices within this investigation. This would be of benefit for both healthy populations as part of a preventive training intervention and with clinical populations during rehabilitation, such as those with CAI and/or anterior cruciate ligament reconstruction. The novel block device that was used within this investigation also is worth further exploration on its own. The block itself comes in several sizes that are dependent upon the body weight of the individual. All participants in this investigation used the size 13 block, which is to be used with individuals under 86.36 kg (190 lbs) based on the manufacturer recommendations. It would be of interest to examine whether the use of a larger block with the same demographics as the current investigation has an impact. Moreover, the block had five removable inserts within the foam. All five inserts were left in place during this investigation. However, removing these inserts may influence the way that the foam deforms and thus change the CoP parameters. As discussed earlier, future investigations should examine the longitudinal effects of training with different instability devices. The block that was used within this study may have the ability to add additional overload stresses over time placed on the removable inserts. Thus, examining these effects would be of interest to practitioners who use the device but also to researchers who aim to develop training protocols to be used across different population groups. This study is not without limitations. The participants were not given specific instructions on positioning the nondominant leg during testing. Previous studies have instructed subjects to flex the nondominant knee at 90 degrees [23]. However, other studies have also not used specific instructions as to the location of the contralateral limb when trying to replicate clinical settings. As the present study aimed to have a level of ecological validity, it was believed that not providing specific instructions on the location of the contralateral limb was appropriate [23]. Instructing subjects to keep the nondominant leg at 90 degrees could have led to lower ecological validity. A second limitation of this study was the visual field. The visual target on the wall was not at eye level, which could have increased the postural sway due to the head's orientation [24]. As all participants used the same visual target across all conditions, any impact would have been the same in each condition. Lastly, during data collection, this investigation was performed on a sample of healthy young adults free of neuromuscular disorders and injury-free. Thus, the generalizability across injured populations commonly using single-limb balance training is limited. However, balance training protocols are not limited to those individuals who are currently injured and can be used in an injury mitigation capacity. Thus, the use of a healthy, college-aged population does provide a level of informative data to be used in the design of future training interventions.