Physical activity and its associated factors in frail geriatric patients: a cross-sectional study utilizing the COM-B model

Background: Frail geriatric patients have low adherence to physical activity, which is a critical concern as exercise intervention is a key method for managing frailty. The Capability Opportunity Motivation-Behaviour (COM-B) model provides a framework for understanding factors related to health behaviour. However, few studies have applied this model to investigate physical activity in hospitalized frail patients. Methods: From February to June 2025, a questionnaire survey was conducted on 432 frail geriatric patients. Physical activity was assessed using the International Physical Activity Questionnaire-Short Form. Drawing on the COM-B model as an organizing framework, data on potential correlates were collected using a general information questionnaire, the Geriatric Locomotive Function Scale, the Family APGAR index, and the Revised Behavioural Regulation in Exercise Questionnaire-3. Results: The total metabolic expenditure during physical activity for frail geriatric patients was 1521 (IQR: 495, 3786) MET-min/week, with an average daily sedentary time of 8.7 ± 1.8 h. Only 81 participants (18.8%) met the guidelines for physical activity. Hierarchical multiple linear regression analysis identified six significant factors associated with physical activity(R²=0.300): family support and behavioural regulation were positive correlates, whereas geriatric locomotive function, increasing age, number of chronic diseases, and medication status were negative correlates. Structural equation modelling explained 29.3% of the variance in physical activity. Mediation analysis showed that geriatric locomotive function and family support were directly associated with physical activity (direct effects of -0.263 and 0.159, respectively; P < 0.001) and also indirectly associated via behavioural regulation (indirect effects of -0.041 and 0.035; P < 0.05). Conclusions: This study suggests that physical inactivity among frail geriatric inpatients is associated with geriatric locomotive function, family support, and motivation, alongside physiological constraints including age, comorbidities, and polypharmacy. Behavioural regulation emerged as a key mediating factor in these relationships. The findings suggest that interventions referencing the COM-B framework might benefit from targeting these specific functional and motivational correlates. Clinical trial number: Not applicable.