Body sway during quiet standing post-stroke: effects of individual and interpersonal light touch

Lightly touching an external reference, whether a fixed point or another person, reliably improves postural stability. In hemiparetic stroke patients, however, the effect of fixed point light touch (LT) on balance is uncertain. Moreover, it is not clear whether stroke patients respond in the same manner as healthy controls to light interpersonal touch (IPT). In the present study, therefore, the effects of LT and IPT on balance were contrasted in older adults with and without chronic hemiparetic stroke. Participants stood with open eyes in comfortable, normal bipedal quiet stance and performed 4 contact conditions in random order: no contact, fingertip LT, active fingertip IPT and passive elbow IPT. Body sway varied in response to the contact condition in both groups. The hemiparetic patients, whose impairment was relatively mild, showed responsiveness to LT and IPT similar to the non-hemiparetic group in terms of proportional sway reduction in the anteroposterior but not in the mediolateral sway direction. This indicates that light touch effects are robust but cannot be generalized from healthy older adults to hemiparetic stroke patients without consideration of moderating functional constraints of the individual and the specific postural context. Future research should include hemiparetic individuals with moderate to severe postural deficits to determine possible limitations of light touch balance support in stroke.