Posture and vision: How different distances of viewing target affect postural stability and plantar pressure parameters in healthy population

Background: Postural stability is maintained by the Postural Control System (PCS), consisting of anatomical structures of Central Nervous System and peripheral receptors, interacting with each other, in order to keep whole-body balance by modulating the myofascial chains against gravity. The vision is one of the most important peripheral receptors for postural control. Previous studies analyzed the changes of body sway during viewing nearby (VNT) and distant (VDT) targets in healthy population without considering the feet adaptations related to the body weight distribution. Aim of this study was to investigate how different distances of viewing target affect the variability of postural stability and plantar pressure parameters in healthy subjects. Methods: 31 stabilometric and plantar pressure parameters were acquired in 20 young healthy subjects by baropodometry performed in bipedal standing during VNT and VDT (0.70 m and 3 m from the heels, respectively). Variability and statistical differences between VDT and VNT were implemented. Results: Results showed the highest repeatability for plantar pressure parameters, a slightly high for CP speed and a lowest for CoPsa and Length Surface Function during both VNT and VDT. Moreover, a significant increase of load percentage on left-foot and right-Forefoot, of mean and maximum pressures on left-Forefoot, of CoPsa and CPspeed and a decrease of LSF were found during VDT. Discussion: This study revealed how a greater distance of viewing target affects body-weight distribution and increases body oscillations. These findings highlighted the importance of visual target distance for the correct interpretation of postural stability and plantar pressure parameters, and the need to standardize target distance during stabilometric exam.