Operationalizing wellness in physiotherapy: development and validation of a 0–100 wellness physical therapy index from a national population survey

BACKGROUND: Physiotherapists are increasingly expected to promote physical activity and reduce sedentary time, but there is no simple, field-specific metric that summarizes these behaviors for everyday practice. OBJECTIVE: To develop a 0-100 Wellness Physical Therapy Index (WPTI) combining domain-specific physical activity and sedentary time, and to examine its validity and potential clinical utility in a national sample of adults. METHODS: A cross-sectional secondary analysis of the Sasakawa Sports Foundation "Sports Life Survey 2024 (Adults)" was conducted. Leisure and transport physical activity (min/week) and sedentary time (min/day; reverse-coded) were winsorized and transformed into standardized scores. Principal component analysis generated data-driven weights used to construct the Wellness Physical Therapy Index (WPTI) and rescale it from 0 to 100. Analytic survey weights were constructed using raking with trimming. Distributional properties, internal consistency, convergent validity with total metabolic equivalent (MET) minutes/week, and criterion validity for achieving the World Health Organization (WHO) guideline (≥600 MET-minutes/week) were evaluated using weighted regression, receiver operating characteristic analyses, and restricted cubic splines. RESULTS: Among 2966 adults with complete data, the mean weighted WPTI score was 20.9 (standard deviation (SD) 11.3). The index showed acceptable internal consistency and moderate correlations with total MET-minutes/week. Higher WPTI scores were strongly associated with meeting the World Health Organization guideline (odds ratio per 10-point increase 19.9, 95% confidence interval 15.7-25.2). Discrimination was excellent (area under the curve 0.865) with good calibration and robust results across sensitivity analyses. CONCLUSIONS: The WPTI provides a practice-ready, physiotherapy-specific index that integrates domain-specific activity and sedentary time into a single 0-100 score. It may support rapid screening, communication about movement and sitting, and the translation of population surveillance data into routine physiotherapy practice.