Development and validation of an instrument to measure beliefs in physical activity among (pre)frail older adults: An integration of the Health Belief Model and the Theory of Planned Behavior

To develop and evaluate the psychometric properties of an instrument assessing beliefs in physical activity based on the integration of the Health Belief Model (HBM) and the Theory of Planned Behavior (TPB) among (pre)frail older adults.A literature review and semi-structured interviews were conducted to generate the initial item pool of the instrument. A rural sample of 611 (pre)frail older adults was enrolled to examine the validity and reliability of the instrument.The exploratory factor analysis extracted eight factors for this instrument, explaining 71.3% of the variance in beliefs in physical activity. The confirmatory factor analysis confirmed the eight-factor structure. Linear regression models found that the integrated HBM-TPB constructs explained 65.9% of the variance in physical activity intention and 13.6% in physical activity. The Cronbach's alpha coefficients for the factors ranged from 0.80 to 0.98, and ICCs ranged from 0.71 to 0.85.This instrument has satisfactory construct validity, predictive validity, internal consistency reliability and test-retest reliability, and it can be used in (pre)frail older adults to measure beliefs in physical activity.This instrument may help health care providers understand beliefs in physical activity and facilitate targeted interventions among (pre)frail older adults.