What's in a Message? Effects of Mental Fatigue and Message Framing on Motivation for Physical Activity.

Many adults worldwide do not meet current physical activity (PA) guidelines. Mental fatigue decreases the likelihood of choosing to engage in PA. Message framing may enhance PA motivation when fatigued. We examined the effects of mental fatigue and message framing on PA motivation with additional focus on the messaging "congruency effect." Three hundred and twenty undergraduates completed measures of dispositional motivational orientation and were exposed to either gain-framed or loss-framed messages before completing an effort discounting questionnaire. Results showed lower motivation to engage in PA of higher intensities and longer durations. Direct effects of message framing on PA motivation were not significant. Interaction effects revealed that participants receiving messages congruent with their dominant motivational orientation showed increased motivation for light-intensity PA and decreased motivation for vigorous-intensity PA as mental fatigue increased. Findings suggest that providing messages congruent with one's dominant motivational orientation may increase motivation for engaging in light-intensity PA when fatigued.