How does mindfulness shape affective experience during exercise? A think-aloud study of real-time psychological processes.

Positive affect during exercise is a key predictor of continued participation, yet the mechanisms through which mindfulness-based exercise influences affect remain largely inferred from retrospective, outcome-focused designs. This study used a think-aloud (TA) methodology to capture consciously accessible, moment-to-moment experience during exercise and to test whether a single bout of mindfulness-based exercise alters affect via in-task process shifts. Thirty-six adults were assigned to low or high habitual physical activity groups and completed three counterbalanced sessions of 20-min moderate-intensity treadmill running under mindfulness, distraction, and control conditions. Affective valence was assessed pre-, during, and post-exercise using the Feeling Scale. TA verbalizations recorded during exercise were transcribed and coded into theoretically grounded themes reflecting interoceptive monitoring, active self-regulation, external monitoring, and distraction. A process-level Internal Orientation Index (IOI) was computed to index the balance of internally versus externally oriented processes. Mixed-effects models showed that mindfulness robustly increased IOI relative to both distraction and control, indicating a consistent shift toward real-time interoceptive monitoring and adaptive self-regulation during exercise. Window-level analyses provided no compelling evidence of systematic temporal modulation across the bout. Conclusively, the TA evidence demonstrates that mindfulness changes how exercise is experienced in real time by strengthening internal monitoring and regulation, offering direct process-level support for proposed mechanisms of mindfulness-based exercise.