A three-arm pilot rater-blinded randomized controlled trial is conducted, comprising Yoga-based Group Intervention (YoGI + TAU) as the experimental condition, a strength and flexibility training (SFT + TAU) group, and treatment as usual (TAU). Participants in all conditions receive the respective intervention in addition to treatment as usual (TAU) in outpatient settings in Germany. The interventions are designed for patients with schizophrenia spectrum disorders. To examine feasibility, acceptability, and preliminary efficacy, self-report measures and blinded rater-based assessments are administered at baseline (T0), after 12 weeks of participation (T1), and at a 3-month follow-up (T2). Before each intervention session, acute stress (general stress and symptom-related distress) is measured using a visual analogue scale. After each intervention session, acute stress (general stress and symptom-related distress; visual analogue scale), perceived effort (BORG-RPE-Scale), and the occurrence of unpleasant experiences are recorded via self-report, while instructors rate exercise performance and overall participation quality. In addition, semi-structured interviews are conducted at T0 and T1 to assess subjective mechanisms of change and relevant processes.
The primary outcomes of this trial are the feasibility and acceptability of YoGI and the SFT, assessed through recruitment and retention rates, adherence, and participant feedback. Based on recommendations for pilot studies of 20-50 participants, a conservative target sample size of 60 patients was determined. Further, the trial will evaluate secondary outcomes, including (body) mindfulness (SMQ, BMQ), symptoms of depression, anxiety, and stress (DASS, CDSS), positive and negative symptomatology (PANSS), psychological flexibility (CFQ), psychological well-being (WHO-QoL-BREF), social functioning (PSP), subjectively perceived cognitive functioning (SSTICS), and physical activity (SIMPAQ). This study aims to provide preliminary evidence for the efficacy of YoGI in comparison to both SFT and a TAU, and to establish a foundation for a future fully powered randomized controlled trial.