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

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. 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. 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. 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. 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.