Self-determined motivational health coaching ('SAMI') during outpatient treatment to promote physical activity of people with serious mental illness: a pilot controlled trial.

Background: Brief motivational coaching, integrated into health care; seems promising to address physical inactivity of people with serious mental illness (SMI).

Aims: To test the impact of a self-determined health coaching approach (the "SAMI" intervention) during outpatient mental health treatment on moderate-to-vigorous physical activity (MVPA) of people with SMI.

Methods: Adults (mean age = 41.9, SD = 10.9) with an ICD-10 diagnosis of mental illness were semi-randomized to the SAMI-intervention group (IG) or control group (CG). The IG received 30 minutes of health coaching based on the self-determination theory (SDT). MVPA and sedentary time (ST) were measured with the International Physical Activity Questionnaire - short form (IPAQ-SF) and symptoms of mental illness with the Brief Symptom Inventory (BSI-18), each at baseline and follow-up (3-4 months). Differences in primary (MVPA) and secondary (ST, BSI-18) outcomes were evaluated using negative binomial regressions and general linear models.

Results: In the IG (n = 30), MVPA increased from 278 (interquartile range [IQR] = 175-551) to 435 (IQR = 161-675) min/week compared to a decrease from 250 (IQR = 180-518) to 155 (IQR = 0-383) min/week in the CG (n = 26; adjusted relative difference at follow-up: Incidence Rate Ratio [IRR] = 2.14, 95% CI: 1.17-3.93, p = 0.014). There were no statistically significant differences in ST and BSI-18.

Conclusions: Brief self-determined health coaching during outpatient treatment could increase post-treatment MVPA in people with SMI, potentially up to a clinically relevant level. However, great uncertainty (for all outcomes) weakens the assessment of clinical relevance.