The overall goals of this project are to examine the efficacy of exercise priming (i.e., intentional sequencing of aerobic exercise immediately prior to cognitive behavioral therapy ['ActiveCBT']) to treat depression.

Specific aims are to 1) demonstrate the effects of exercise priming on mechanisms associated with therapy success (i.e., working alliance, behavioral activation) and 2) determine the efficacy of exercise priming for treatment of depression and strength of relationship with engagement of target CBT mechanisms.

The primary outcomes of this trial are participant-rated working alliance and change in behavioral activation each averaged across all eight sessions. Secondary outcomes include post-intervention depressive scores (Hamilton Depression Rating Scale).

For safety, suicide severity will be evaluated using the Columbia-Suicide Severity Rating Scale.