The relation between falls risk and movement variability in Parkinson's disease.

Falls are a major health concern for older adults with Parkinson's disease (PD). This study was designed to examine differences in falls risk and its relation to changes in the average and variability (i.e. intra-individual variability) of reaction time (RT), finger tapping, standing balance and walking between healthy older adults and persons with PD. Thirty-nine adults with PD (70.0 ± 8.1 years) and 29 healthy older adults (66.8 ± 10.4 years) participated in this study. Falls risk (using the physiological profile assessment), gait, RT, balance and tapping responses were assessed for all persons. Results demonstrated that individuals with PD exhibited a greater risk of falling coupled with a general slowing of motor function covering declines in walking, RT and finger tapping. In addition, the movement responses of the PD group were more variable than the healthy older adults. Correlation results revealed group differences with regards to the neuromotor measures which were significantly correlated with falls risk. For the PD group, gait measures were highly correlated with their falls risk while, for the healthy older adults, falls risk was linked to balance measures even though PD persons had increased sway. Overall, persons with PD were at greater falls risk, moved slower and with increased variability compared to the healthy older adults. Further, while there are some similarities between the two groups in terms of those measures related to falls risk, there were also several differences which highlight that persons with PD can have different risk factors for falling compared to healthy adults of similar age.

Chronic impairments of static postural stability associated with history of concussion.

Postural stability deficits are commonly observed in cases of concussion. However, the objective duration in which impairments of standing postural stability remain following a concussion is often inconclusive. The present study was conducted to determine if prior history of concussion is associated with deficits in postural stability beyond the clinical determination of recovery. It was hypothesized that concussion history would be associated with decreases in static stability compared to individuals that have never sustained a concussion. Fifty-four healthy adults were recruited based on whether they reported sustaining one or more prior concussions (n = 27) or no history of concussion (n = 27). Participants were instructed to stand on a force platform to track center-of-pressure (CoP) during standing for thirty seconds under four conditions based on stance and number of tasks: (1) bipedal, single-task, (2) bipedal, dual-task, (3) unipedal, single-task, and (4) unipedal, dual-task. Results revealed that individuals with a history of concussion demonstrate significantly reduced postural stability under dual-task conditions as evidenced by increases in average displacements and elliptical area of postural sway as well as reductions in CoP sample entropy. However, there were no significant differences in CoP displacement or elliptical area between groups under single task conditions. Overall, these findings indicate that concussion is associated with impairments of maintaining standing postural stability that remain evident approximately 7 years following clinical resolution of the initial injury. The exacerbation of these impairments under dual-task conditions indicate that concussion can result in a reduced capacity to allocate proper attention resources to multiple concurrent objectives.