[Capabilities for Physical Activity in Older People: Development and Testing of a Measurement Tool]

Based on Sen's capability approach, this study addresses the operationalization of capabilities for leading an active lifestyle. By assessing capabilities, processes of change can be mapped and the development of interventions to promote physical activity in different population groups, e. g., older adults, can be supported. However, no standardized German-language instrument for measuring physical activity-related capabilities is available to date.

Building on an exploratory interview study (Sauter et al., 2019) that identified relevant physical activity-related capabilities in older adults, a standardized questionnaire with 41 items was designed. Two different question formulations were designed to query perceived capabilities for physical activity. The "think-aloud" method was conducted to validate the instrument. This involved recording all verbal comments made by participants while completing the questionnaire and conducting supplementary interviews for comprehensibility and applicability. The sample included 16 older adults (w=9, MW=66.3 years).

Overall, respondents rated the instrument's usability and comprehensibility as good. For the questioning of perceived capabilities, the formulation "I have the possibility to..." was favored instead of "I perceive my personal opportunities as…". Difficulties in understanding and ambiguities were found in a few items. Thus, further changes were made to specify these questions with regard to unclear terms such as "walking paths".

The questionnaire seems to be suitable to asses perceived capabilities for leading an active lifestyle in older adults. The final questionnaire is available in English and in German. Further research is needed to test the applicability of the instrument in other population groups and verify objectivity, reliability and validity.