Physical Fitness Index for Older Adults in a Chinese Retirement Community.

BACKGROUND: Physical fitness is important for health and independence in older adults, but existing systems do not always provide a continuous multidomain score. OBJECTIVE: To develop and preliminarily evaluate a Physical Fitness Index (PFI) for older adults in a Chinese retirement community. METHODS: A total of 561 participants aged 65-89 years completed assessments of body composition, strength, endurance, balance, mobility, and flexibility. Scores were normalized within sex and 5-year age groups and combined using a fixed radar-axis order. RESULTS: The PFI averaged 39.24 ± 13.43 points (range, 4.16-84.47). In a reduced surrogate regression model, R2 was 0.825 and ten-fold cross-validation yielded an RMSE of 5.79 points and an MAE of 4.33 points. CONCLUSION: The PFI provides a continuous overall score with a domain profile, but its calibration and measurement properties require external and longitudinal validation.