Catherine Reed¹ (clreed@cmc.edu), Chandlyr Denaro¹, Joseph Asta¹, Alan Hartley¹, Jenna Monroy²; ¹Claremont McKenna College, ²Natural Sciences, Claremont Colleges

Aging affects attention and executive control, making it more difficult to split focus between walking (motor) and thinking (cognitive), thereby increasing fall risk. Cognitive-motor dual tasks require simultaneous performance across tasks. Prioritization theory assumes shared resources between cognitive and motor tasks and predicts biomechanical stability is prioritized as motor difficulty and cognitive difficulty increase. However, few studies systematically vary both cognitive and motor difficulty to determine the conditions under which processes are prioritized. We investigated how cognitive and motor difficulty affect biomechanical and cognitive performance variables in younger and older adults. Participants walked at preferred speeds on a treadmill while performing auditory n-back working memory tasks. Cognitive load varied across 0-, 1-, and 2-back tasks. Motor load varied across 0-, 2.3-, and 4.6-degree inclines. Results showed cognitive performance was affected by biomechanical difficulty and cognitive load. For both groups, d-primes declined with increased load, but the decline was greater for older adults. Kinematics were affected by age, incline and cognitive load. Relative stride length and percent time in double support increased with incline, replicating effects of motor load on biomechanics. In older adults, kinematics changed with increased cognitive load particularly with the onset of incline, suggesting a prioritization of biomechanical stability. Our results suggest a non-linear relationship between cognitive load, biomechanical difficulty and performance, with younger and older adults reaching peak performance at different levels of combined cognitive and motor difficulty. Future studies on aging populations will investigate the allocation of resources while parametrically increasing both tasks.

Acknowledgements: NSF DUE 2400479, 2227412 & 1914855