Plantar Exteroceptive Inefficiency causes an asynergic use of plantar and visual afferents for postural control: Best means of remediation

Introduction: Some subjects have difficulty to integrate both visual and plantar inputs, showing at the same time a postural blindness and a Plantar Exteroceptive Inefficiency (PEI). The former corresponds to a better stability eyes closed (EC) than eyes open (EO), while the latter is defined as a better stability on foam than on firm ground. Clinical studies reported that a manipulation of either plantar or visual input could affect the weight of both cues in postural control, suggesting interdependence in their use. The purpose of the experiment is to characterize the PEI phenomenon better and see if such synergy can be objectified. Methods: We recruited 48 subjects (25 +/- 3.3 years) and assessed their balance with a force platform, EO, EC, at 40 or 200 cm, on firm ground, Depron (R) foam, Dynachoc (R) foam, or on a 3 mm-thick Anterior Bar AB (R). We assessed their sensorial preferences through their PQ and RQ. Results: The main results are that there normally exists a synergy in the use of plantar and visual afferents, but only at 40 cm and in the absence of PEI. Conclusions: Plantar Exteroceptive Inefficiency interferes with the role of vision in postural control, its effects are distance specific, are better revealed by Depron (R) foam and the AB (R) improves posture but does not solve visual-podal asynergy. These results also have clinical interests as they indicate the best way in terms of distance and choice of foam to diagnostic PEI. Finally, they suggest restricting the use of the AB (R), commonly employed. These findings can be useful for clinicians concerned with foot, eye, and posture.