## 4 Discussion
### Potential Application for Postural Control Training and Rehabilitation  
Healthy individuals are able to effectively maintain postural control under lower instability levels, even when sensory input is reduced [36]. While falls are a significant concern in older populations, postural control is equally important for injury prevention and motor function in younger, active individuals, highlighting its broader relevance across age groups. Furthermore, postural control can be maintained under various instability levels, provided that sufficient sensory information is available. However, the reliance on sensory information becomes more critical as the level of instability increases [30]. This phenomenon is exemplified when comparing the increase in chest movement volume from the Basic to Vestibular strategy: while the chest movement volume increases only 123% from 1 to 3 IL under the Basic strategy, the increase is much more significant in the Vestibular strategy, reaching 280%. Furthermore, the percentage increases in chest movement volume observed across different sensory strategies and instability levels indicate how the postural control system adapts under varying conditions. These findings suggest that greater reliance on compensatory chest movements occurs when instability or sensory limitations challenge the body's balance mechanisms. These findings have practical implications for real-life scenarios, such as walking on uneven terrain or in environments with reduced visibility, where the ability to manage increased body sway is crucial for preventing falls. These insights can inform  
Figure 10: Principle of interaction of sensory information and instability level. The gray area (I) represents COM (center of mass) and BOS (base of support) movement while standing on a stable base. rehabilitation protocols, helping to train individuals to better integrate sensory inputs and manage instability, particularly for those at risk of balance disorders. The integration of sensory systems has been successfully reported in clinical settings by both earlier and recent studies [37]. Additionally, the study's findings indicate that the body's postural control can be maintained effectively with certain combinations of IL and SIS, such as 2 IL-Visual and 2 IL-Proprioception. Despite the differing amounts of sensory input in these strategies, the effects on postural control are similar. These findings suggest that, in the event of sensory deficits, healthy individuals can substitute other sensory information to support postural control [31; 32]. By applying combinations of instability levels and SIS, it is possible to significantly enhance the effects of the sensory integration strategy. Even in healthy individuals, a high level of instability can be created without external perturbation. The level of instability can be adjusted across a wide range of destabilization--from very minimal to severe, where even healthy young individuals may struggle to compensate and maintain balance. In clinical contexts, these findings hold potential for aiding the treatment of balance disorders stemming from sensory deficits, such as those related to vision impairment, peripheral neuropathy, or vestibular dysfunction. The strategic application of varying instability levels could potentially enhance the interaction of dominant sensory inputs, thereby improving balance control. This underlines the necessity of understanding and manipulating the sensory strategy--instability interplay for more effective therapeutic outcomes. A wide range of destabilization levels (by combination of IL and SIS) allows patients to choose the most suitable and safe level of instability, without the need for any external force. This feature facilitates personalized balance training and rehabilitation, catering to the individual needs and abilities of each patient. This tailoring of balance exercises is crucial in ensuring that the exercises are both safe and effective, furthering patient recovery while minimizing the risk of injury.