This 16-week, three-group, nonrandomized interventional study evaluated whether the weekly frequency of a brief classroom-based physical exercise program was associated with changes in mental health and physical activity among 105 undergraduate medical students at Universidad Tecnologica de Pereira, Colombia. EG2 (n=35) received two exercise sessions per week, EG1 (n=37) received one session per week, and CG (n=33) received no exercise intervention. Anxiety, depression, stress, and physical activity were assessed at baseline and after 16 weeks.