The Role of Visual Target Distance in Postural Stability: Insights for Therapists

Postural stability, a critical component of balance, is regulated by the central nervous system through interactions with peripheral sensory receptors, including visual, vestibular, stomatognathic, and somatosensory systems. Among these, the visual system plays a dominant role in maintaining balance during both static and dynamic conditions. Visual fixations, which enable the eyes to focus on a specific target, are essential for postural control, as they significantly influence balance and stability.

A study from Italy investigates the effects of viewing targets at different distances on postural stability and plantar pressure parameters in healthy individuals, aiming to determine the optimal target distance for reliable postural assessments.

Methods

Twenty healthy participants aged 20 to 22 years were evaluated in an upright posture using a pressure plate system. Two target distances were analyzed: a nearby target placed at 0.70 meters and a distant target at 3 meters. Stabilometric parameters (such as center-of-pressure sway area and speed) and plantar pressure parameters (load distribution and pressure in foot regions) were measured. Intra-subject variability across trials was also assessed to evaluate the consistency of these parameters.

Key Findings

1. Impact of Target Distance on Postural Stability:
   • Viewing a nearby target resulted in lower variability and greater postural stability compared to viewing a distant target. Distant targets increased center-of-pressure sway area and speed, indicating greater instability.
2. Changes in Weight Distribution:
   • A distant target led to a shift in body weight distribution toward the non-dominant foot, likely as a compensatory mechanism to maintain balance.
   • In the dominant foot, there was an anterior shift in load, while the non-dominant foot exhibited increased pressure in the forefoot region.
3. Variability in Parameters:
   • Nearby targets exhibited more consistent (lower variability) plantar pressure parameters, while distant targets increased variability, particularly in midfoot pressure and load distribution.
4. Postural Adaptations:
   • The midfoot played a significant role in compensatory postural adaptations when viewing distant targets, likely due to its sensitivity to tactile and vibratory stimuli.

Clinical Implications

The findings emphasize the importance of target distance in postural assessments. Viewing distant targets introduces greater variability in postural stability and plantar pressure parameters, potentially complicating the interpretation of results. Therapists should consider these effects when designing assessments and training protocols.

Recommendations for Practice

• Standardize Target Distance: To reduce variability and improve reliability, visual targets should be placed at approximately 0.70 meters from the participant’s heels during stabilometric examinations.
• Target Distance and Balance Training: For balance training or postural assessments, using nearby targets may offer better control and lower variability in postural parameters.
• Address Individual Differences: Consider the role of peripheral systems (e.g., vestibular or somatosensory) in postural control and adapt protocols to individual needs.

Conclusion

The distance of the visual target significantly influences postural stability and weight distribution. Placing the target at a standard distance of 0.70 meters ensures more consistent measurements, aiding in the accurate assessment of postural control and plantar pressure parameters. These findings highlight the critical role of visual target distance in clinical evaluations and therapeutic interventions aimed at improving balance and stability.