Mental fatigue, anticipated effort, and subjective valuations of exercising predict choice to exercise or not: A mixed-methods study

Objectives This study examined the effects of mental fatigue on people's decisions to engage in an acute bout of exercise quantitatively, through a sequentially mediated pathway consisting of perceived effort and benefit vs. cost valuations and qualitatively, using exit interviews to survey the conscious reasoning behind participants' choices. Design Mixed methods, randomized, experimenter blind to group. Method Participants (N = 84, M age  = 19.07 ± 1.86 years) completed either a high cognitive demand (incongruent Stroop) task or low cognitive demand (documentary viewing) task for 12 min. Before and after the cognitive task, participants rated their anticipated effort and subjective evaluations (benefits and costs) of engaging in a 20-min moderate-to-vigorous intensity exercise task. After completing the latter ratings, participants chose between the exercise task or a non-exercise task (seated “free time” and use of smartphone or computer). Participants were led to believe they would actually engage in the task; however, once their choice was made, they were not required to complete the task but were invited to complete a semi-structured interview to probe the reasoning behind their choice. Results Serial mediation analyses revealed a significant indirect effect from mental fatigue to choice through perceived effort and benefit vs. cost valuations (95% C.I. = −0.01 to −0.0004). Qualitative data, organized by categories based on group/choice pairings, yielded twelve unique codes explaining how the cognitive tasks affected choice. Conclusions Results demonstrate mental fatigue alters decision-making through a sequentially mediated process including subjective perceptions of effort, benefits, and costs. Interview responses also highlight the individual-level consequences of completing cognitively demanding and non-demanding tasks on effort-based decision-making. Future research should explore additional feeling states as they relate to people's choices to engage in exercise or sedentary behaviors.