Cognition and action are often intertwined in everyday life. It is thus pivotal to understand how cognitive processes operate with concurrent actions. The present study aims to assess how simple physical effort operationalized as isometric muscle contractions affects visual attention and inhibitory control. In a dual-task paradigm, participants performed a singleton search task and a handgrip task concurrently. In the search task, the target was a shape singleton among distractors with a homogeneous but different shape. A salient-but-irrelevant distractor with a unique color (i.e., color singleton) appeared on half of the trials (Singleton distractor present condition), and its presence often captures spatial attention. Critically, the visual search task was performed by the participants with concurrent hand grip exertion, at 5% or 40% of their maximum strength (low vs. high physical load), on a hand dynamometer. We found that visual search under physical effort is faster, but more vulnerable to distractor interference, potentially due to arousal and reduced inhibitory control, respectively. The two effects further manifest in different aspects of RT distributions that can be captured by different components of the ex-Gaussian model using hierarchical Bayesian method. Together, these results provide behavioral evidence and a novel model for two dissociable cognitive mechanisms underlying the effects of simple muscle exertion on the ongoing visual search process on a moment-by-moment basis.

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Research assessing the effects of age on physical actions and cognitive processes is often conducted in isolation. However, action and cognition often interact in daily functions and deteriorate with age. Therefore, assessing how motor actions affect core cognitive abilities and how age amplifies these effects is pivotal. The present study tested the effects of effortful physical exertion (isometric handgrip) on working memory (WM) and inhibitory control in young 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, MVC). Given our previous understanding that high physical exertion impairs inhibitory control, we hypothesized 1) inhibitory control of access to WM will be compromised under high physical exertion and 2) this effect will be amplified by age. Effortful physical exertion, although failed to affect WM accuracy with 0-distractors present for both age groups, reduced WM accuracy for the older, but not young adults, with 5-distractors present. Similarly, older adults experienced greater distractor interference with 5-distractors present under high physical exertion, indexed by slower reaction time (RT), confirmed by hierarchical Bayesian modeling of RT distributions. Our findings that a simple but effortful physical task may result in impaired cognitive control may be empirically important for understanding everyday functions of older adults. Reduced inhibitory control and physical abilities may pose a problem for older adults as the negative interactions between cognitive and motor tasks may impair daily functions and possibly increase the risk of injury.

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