Using kinetic and kinematic parameters to explain changes in gait due to cognitive tasks
Seymour, Kelly M.
University of Delaware
Although historically considered an automatic process, gait control has been shown to consume attentional demands, supported by the concept of dual-tasking with a motor and cognitive challenge. Identifying the impact of cognitive challenges on motor tasks in healthy younger and older adults could detect increased fall risk and lead to prevention strategies for at risk populations, such as the elderly or cognitively impaired. The impact on kinetics, kinematics, and spatiotemporal variability due to dual-tasking is currently unknown. The objective of this study is to identify how dual-tasking impacts motor task performance in healthy younger and older adults. Eleven healthy younger (20.1 ± 1.9 years) and eleven healthy older (60.5 ± 9.4 years) adults first completed a neuropsychological assessment consisting of various cognitive tests to define a baseline measure of cognitive abilities. Three tasks were repeated during treadmill walking: a working memory task (Paced Auditory Serial Addition Test, PASAT), a visual attention and processing speed task (Symbol Digit Modalities Test, SDMT), and a visual attention and fine motor skills task (cellular phone dialing task, Phone). Three walking conditions were used for dual-tasking: self-selected, fast (120% of self-selected), and limp (induced by the instrumented split-belt treadmill with one belt moving at self-selected speed and one belt moving at fast speed). Kinetic, kinematic, and spatiotemporal parameters were recorded, and statistical analysis (ANOVA) was run separately for older and younger adults with cognitive test as the independent variable. Under dual-task conditions, it was found that mean stride width increased for younger adults during the fast (p = 0.028) and self-selected (p = 0.034) walking conditions while performing the SDMT task compared to walking with no cognitive challenge. In addition, both younger and older adults displayed trends of decreasing stride length and increasing stride width with the addition of all three dual-tasks under all three walking conditions. Also, younger adults showed an increasing trend in stride length and width variability under all three walking conditions for the SDMT dual-task challenge. Finally, older adults showed a decreasing trend in hip and knee range of motion with the addition of all three dual-tasks at all three walking conditions. Dual-tasking produced few significant results for both healthy younger and older adults. These results could be due to a number of factors. First of all, a number of parameters had a large effect size (>0.14), suggesting limited statistical power. This could be due to large standard deviations and/or a small sample size. In addition, under controlled speed conditions participants had to compensate for a situation in which they would normally slow their walking speed. Because walking speed and kinematic parameters are often confounded, keeping a constant walking speed may have also led to constant gait patterns under dual-task conditions. Furthermore, participants may have adopted a "posture-first" strategy in which the motor task was prioritized at the expense of the cognitive task. This would result in the normal gait patterns seen in this study during dual-tasking. Dual-tasks may increase fall risk in older adults if the gait changes are indicative of a fall, such as decreased stride length, increased stride width, increased variability of stride length and width, or decreased hip or knee range of motion. Although not statistically significant, these trends are displayed for both healthy younger and older adults in this study. Because healthy individuals trend toward these gait parameters while dual-tasking, it is probable that the elderly or cognitively impaired would show significant changes in these parameters while dual-tasking, which could put vulnerable populations at risk for a fall. Future implications include developing prevention strategies for older adults at risk of falls.