1. Introduction
stroke, balance disorders
STROKE, PARKINSON DISEASE
Postural control is based on interpreting sensory information from the somatosensory, vestibular, and visual systems. The relative sensory reweighting of each of these inputs depends on the goals of the task and environmental context.Although the relationship between balance ability and verticality has been recognized, causality remains unclear. Gravity perception has been discussed as a possible mechanism for verticality judgment, suggesting that it is an important factor in postural control.Therefore, it is important to evaluate the effects and mechanisms of seated balance training using evaluations of center of gravity (CoG) and postural control. We hypothesized that the relationship with gravity perception could be clarified by evaluating the subjective postural vertical (SPV) and analyzing sitting pressure during sitting balance training.The accurate perception of sitting pressure is essential in maintaining an upright stance; it is a crucial aspect of balance and postural verticality perception by the somatosensory system.It has been demonstrated that sitting pressure and SPV were biased toward the left side in a study of the right hemisphere.Adapting to sitting pressure as a balance ability is an important aid in stroke rehabilitation because it is predicted to contribute to the reconstruction of sensory integration, balance, and independence. Further, truncal control is an important predictor of recovery.The present study aimed to assess the effect of lateral sitting truncal-tilt training using a wedge to optimize postural control on sitting pressure in healthy adults. The wedge was placed lateral to the body and was expected to influence sitting pressure perception, although the efficacy and the mechanism of the laterality adaptation are not well understood. Therefore, it was hypothesized that the implementation of lateral truncal tilt training using a wedge would enable modification of postural control through changes in sitting pressure and SPV, hence improving balance ability. In addition, this training may be useful for rehabilitation interventions for patients with stroke or Parkinson disease, which present balance disorders.