A randomised controlled trial of interventions to promote adoption of physical activity in adults with severe mental illness

Adults with severe mental illness (SMI) have lower physical activity (PA) than the general population. Supervised exercise interventions provide high support but may not effectively promote motivation, which is important for behaviour change. Motivational strategies such as PA counselling may target motivation more directly; however, the effectiveness in people with SMI is unclear. This was a randomised controlled trial of interventions designed to promote PA in adults with SMI. Participants were randomised to either: (1) supervised exercise (GYM), or (2) motivational counselling and self-monitoring using fitness trackers (MOT). Group sessions were once/week over 8-weeks. The primary outcome was time spent in moderate-to-vigorous PA (MVPA) assessed using GENEActiv accelerometers worn continuously. Change in MVPA was assessed using the cumulative change from baseline, and as a composition of light activity, sedentary behaviour, and sleep. Sixty-four participants were allocated (63% male, 82% overweight/obese, 59% psychotic disorder). Accelerometer-derived MVPA increased for the MOT group between baseline and post-intervention, and the cumulative sum of change in MVPA from baseline in the MOT group was higher than the GYM group. Compositional analyses showed stable weekly activity profiles, with no significant changes attributable to group allocation. The cumulative change in MVPA was higher for MOT than GYM; however, compositional analyses that considers MVPA as a composition of other daily behaviours showed no change in composition over the intervention period. Exercise interventions should incorporate motivational strategies and supervised exercise; future research should investigate behaviour change interventions with longer durations and more frequent sessions. The trial is registered under the Australian and New Zealand Clinical Trial Registry (ACTRN12617001017314). • Severe mental illness (SMI) is associated with low moderate-to-vigorous physical activity (MVPA). • Motivation (MOT) and exercise (GYM) interventions may impact behaviour change differently. • MOT increased accelerometer-derived MVPA over GYM, but motivation was unchanged. • Compositional analyses indicated no significant differences. • Motivational strategies should be combined with supervised exercise for people with SMI.