Antidepressant effects of exercise in university students - A study protocol

Although physical exercise interventions are effective in reducing depressive symptoms among students, there is limited evidence on psychophysiological indices reflecting underlying neurobehavioral processes. Grounded in the Research Domain Criteria (RDoC) framework (Cuthbert & Insel, 2010), this study adopts a multi-level approach to depressive symptoms, testing a motivation-centered hypothesis whereby physical exercise enhances effort-based decision-making processes (Hird et al., 2024). A randomized controlled trial is planned with a minimum of 46 university students, as determined by an a priori G*Power analysis. Participants will be eligible regardless of depressive symptom severity, but must not be taking antidepressant medication. The intervention group will undergo a supervised four-week outdoor circuit training at moderate intensity, delivered twice weekly for 60 minutes, with adherence monitored via attendance logs and session supervision, while the control group will maintain usual activities. Psychological outcomes will include measures of depression, anhedonia, anxiety, stress, resilience, affect, well-being, and sleepiness. Physiological measures will include HRV, EEG microstate dynamics, and event-related potentials (ERPs) collected during the Apple Gathering Task (AGT), an effort-based decision-making paradigm. Task performance will index motivation. It is hypothesized that the intervention group will show improvements in depressive symptoms and related self-report measures compared to the control group. Physiologically, increased parasympathetic activity (higher HRV), altered EEG microstates (e.g., increased microstate C duration), and enhanced reward-related ERP components (e.g., reward positivity) are expected. Behaviorally, a greater willingness to exert effort for rewards is anticipated. This protocol will provide RDoC-informed evidence linking exercise-induced symptom improvements to motivational and neurophysiological mechanisms.