Effect of high-intensity interval training on cardiorespiratory fitness, physical activity and body composition in people with schizophrenia: a randomized controlled trial.

Background: Exercise may improve cardiorespiratory fitness in people with schizophrenia, however, possible condition-specific cardiorespiratory disadvantages, a scarcity of methodologically sound studies, and conflicting results raise questions about the effect of exercise on maximal oxygen uptake (VO _2max ) in this group. The primary aim of this study, therefore, was to investigate the effect of high-intensity interval training on VO _2max in people with schizophrenia. Second, we sought to determine whether the intervention would have an effect on general physical activity (PA) level and body composition.
Methods: Eighty-two patients with schizophrenia were randomly assigned to supervised high-intensity interval training or computer gaming skills training, performed twice a week for 12 weeks. Oxygen uptake was measured directly, during a maximum exercise session on a treadmill. PA level were assessed using ActiGraph accelerometer, and body composition was assessed by bioelectrical impedance. Differences between groups were assessed by analysis of variance using a univariate general linear model.
Results: There were no significant differences between the groups on any of the cardiorespiratory variables neither at baseline nor after the program. There were also no significant within-group differences in any of the cardiorespiratory fitness variables between the baseline and post-program time points, despite that 61% of the participants performing high-intensity interval training showed a significant increase in workload on the treadmill. However, 47% of the participants in the high-intensity interval training group had a ≥ 5% increase in VO _2max . Participants supervised by mental health care providers with PA competence (e.g. rehabilitation center staff, sport scientist, physical trainer) had a much larger increase in VO _2max compared to participants supervised by mental health workers without such competence, and when adding PA competence to the model, the intervention group increased VO _2max significantly compared to the comparison group. The intervention had no significant effect on PA level or body composition.
Conclusions: The intervention did not improve VO _2max , PA level or body composition but succeeded in increasing workload on the treadmill. With regard to VO _2max , approximately half of the patients may be considered responders.
Trial Registration: ClinicalTrials.gov ; NCT02205684 , registered July 2014.