Background <p>Although regular exercise improves mental health outcomes, barriers such as limited time, low motivation, and lifestyle-related constraints during young adulthood may hinder consistent participation in exercise programmes. Therefore, feasible, short-term, motivation-supported exercise approaches are needed to influence physiological stress markers and psychological wellbeing. This study evaluates the effects of motivational factors (MF), including group exercises, diaphragmatic breathing, and stretching, and a single session of calisthenic exercise (CE) combined with these factors on blood cortisol, depression, anxiety, and stress levels.</p> Methods <p>This study is a three-arm, randomized controlled experimental trial conducted between July 2025 and January 2026 at a public university located in eastern Türkiye. A total of 84 young adults were randomly assigned to one of three groups: the MF + CE (<i>n</i> = 28), the MF (<i>n</i> = 28), and the control (<i>n</i> = 28). The MF + CE group received a 15-minute motivational factors intervention followed by a 30-minute calisthenic exercise program. The MF group received only the 15-minute motivational factors intervention, while the control group received no intervention. Data were collected both before and after the intervention using a Participant Information Form, the Depression, Anxiety, Stress Scale (DASS-21), and blood cortisol level measurements. Data analysis was performed using ANOVA, correlation analysis, and multiple linear regression analysis.</p> Results <p>In the MF + CE group, blood cortisol levels significantly decreased from 8.43 ± 2.03&#xa0;µg/dL to 3.64 ± 0.69&#xa0;µg/dL (<i>p</i> &lt; 0.01), while in the MF group, a significant reduction was observed from 8.63 ± 1.92&#xa0;µg/dL to 5.36 ± 1.03&#xa0;µg/dL (<i>p</i> &lt; 0.05). No statistically significant change was found in the control group (<i>p</i> &gt; 0.05). Significant reductions were observed in both intervention groups in the total and subscale scores of the DASS-21, with the most pronounced decrease observed in the MF + CE group. According to the results of the regression analysis, psychological variables and sociodemographic factors together explained 21% of the variance in cortisol levels.</p> Conclusion <p>A single session of calisthenic exercise combined with motivational factors significantly reduced physiological and psychological outcomes in young adults. Motivational factors alone also decreased these parameters. Blood cortisol levels were predicted by psychological variables and lifestyle factors, including exercise frequency, sleep, and perceived economic status in this study population.</p> Trial registration <p>Trial registered at ClinicalTrials.gov under NCT07398729 (01/25/2026).</p>