Development and validation of the Physical Capacity Score (PiC) to overcome the lack of correlation among traditional physical tests in detecting age-related decline

We developed the Physical Capacity Score, a set of validated and commonly used physical tests for adults, administered through a custom-built hardware and software platform that enables automated data collection and analysis. This study aimed to evaluate the platform’s repeatability, examine age-related differences, and explore the relationships between different physical capacities in a sample of adults. A total of 812 participants (aged 18–68 years, 63.5% female) were recruited. Participants completed six physical tests: finger tapping, handgrip strength, single-leg stance, sit-and-reach, five-times sit-to-stand, and the YMCA 3-minute step test. Outcome data were standardized by gender (z-scores) and analyzed across age groups using ANOVA. Pearson’s correlation coefficient (r) was used to assess redundancy among outcomes, and Principal Component Analysis (PCA) was conducted. In a test-retest analysis, all variables demonstrated coefficient of variation (COV) 0.90, except for CoP path length (COV = 10.5%, ICC = 0.64). Correlations among outcomes were weak (r range: 0.036–0.373). While all physical capacities declined with age (p