Impact of Extremity Manipulation on Postural Sway Characteristics: A Preliminary, Randomized Crossover Study

Evaluate multisegmental postural sway after upper- vs lower-extremity manipulation. Participants were healthy volunteers (aged 21-40 years). Upper- or lower-extremity manipulations were delivered in a randomized crossover design. Postural assessments were made pre-post manipulation, in floor and rocker board conditions. Analysis included traditional balance measures of pathlength and range and sample entropy (SampEn) to examine the temporal structure of sway of the head, trunk, and surface. No statistical changes in pathlength or sway range on the ground surface condition were observed. No increases in the amount of sway occurred in any condition. Chiropractic manipulation of either upper or lower extremities led to reductions in traditional measures of postural control on the rocker board. In the anteroposterior direction (sagittal plane), lower-extremity manipulation led to increased trunk SampEn while on the ground, and conversely a decreased SampEn while on the rocker board. In the mediolateral rocker board condition (frontal plane), manipulation elicited a change in SampEn that differed according to site of manipulation; upper-extremity manipulation increased SampEn, whereas lower-extremity manipulation reduced SampEn. Both upper- and lower-extremity manipulation influenced several measures of postural sway on both the ground and the rocker board. Lower-extremity manipulation improved the organization of sway at the trunk (anteroposterior direction) and the board (mediolateral direction). Given the reduction and reorganization of sway metrics seen in this study, we propose extending this line of research to the elderly who are at greatest risk of increased sway and falls.