Step by Step Back - A Feasibility Study of a Physical Activity Intervention for Adults With Stress-related Exhaustion

Inclusion Criteria * Adult aged 20 to 64 years. * Experiencing stress-related exhaustion, assessed in regular clinical care (for example, symptoms consistent with exhaustion disorder or a closely related stress-related condition). * Symptoms are not in the acute phase (participant is able to engage in outpatient psychological treatment and gradual physical activity). * Elevated fatigue/exhaustion at screening, indicated by scores on screening questionnaires (Karolinska Exhaustion Disorder Scale and Multidimensional Fatigue Inventory). * Able to understand spoken and written Swedish. * Has access to a smartphone, tablet, or computer with an internet connection to complete study questionnaires and activity logging. * No medical condition that makes physical activity unsafe, based on clinical screening and participant self-report. Exclusion Criteria * Currently receiving psychological treatment outside the recruiting clinic that is expected to interfere with participation in the program or study assessments. * Current or past diagnosis of a psychotic disorder. * Current or past diagnosis of bipolar disorder. * Severe mental health condition requiring another primary treatment approach at this time (for example, severe major depressive disorder, post-traumatic stress disorder, or an eating disorder). * Ongoing substance use disorder. * Medical condition or acute illness that makes physical activity inappropriate at this time (for example, recent blood clot, severe infection, or other serious condition). * Severe musculoskeletal condition that substantially limits ability to perform physical activity. * Started antidepressant medication within the past 4 weeks. Additional notes (not eligibility criteria): Participants may use psychotropic medication (for example, antidepressants, sleep medication, or anxiety medication) if the medication regimen is stable. Participants will be asked to report any medication changes during the study period. Mild to moderate comorbid anxiety or depression is allowed if stress-related exhaustion is the primary clinical problem.