Detrimental Effects of Effortful Physical Exertion on a Working Memory Dual-Task in Older Adults

Action and cognition often interact in everyday life and are both sensitive to the effects of aging. The present study tested the effects of a simple physical action, effortful handgrip exertion, on working memory (WM) and inhibitory control in younger and older adults. Using a novel dual-task paradigm, participants engaged in a WM task with 0 or 5-distractors under concurrent physical exertion (5% vs. 30% individual maximum voluntary contraction). Effortful physical exertion, although failing to effect WM accuracy in the distractor absent condition for both age groups, reduced WM accuracy for the older, but not young adults, in the distractor-present condition. Similarly, older adults experienced greater distractor interference in the distractor-present condition under high physical exertion, indexed by slower reaction time (RT), confirmed by hierarchical Bayesian modeling of RT distributions. Our finding that a simple but effortful physical task results in impaired cognitive control may be empirically important for understanding everyday functions of older adults. For example, the ability to ignore task-irrelevant items declines with age and this decline is greater when simultaneously performing a physical task, which is a frequent occurrence in daily life. The negative interactions between cognitive and motor tasks may further impair daily functions, beyond the negative consequences of reduced inhibitory control and physical abilities in older adults.