Background Older people have more leisure time, but many are physically inactive. Momentary feelings of pleasure or happiness and sense of purpose can be sources of intrinsic motivation. This study's objective was to investigate how the type (sedentary, active) and context (social and environmental) of older peoples' activities relate to momentary feelings of happiness and purpose. MethodsDetails of activities, contexts and feelings of retired or semi-retired adults (n=67, aged 50-78y) were

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... ured over 7 days using ecological momentary assessment (EMA) via a smart phone app. Participants were prompted on their smart phone six times at random per day, resulting in 2,065 valid prompts. They wore an Actigraph accelerometer on the waist for 7 days to measure physical activity. Happiness and sense of purpose outcome variables were regressed on activities, context and potential confounding variables (e.g. age, gender, physical activity). Regression standard errors were clustered on participants to account for the hierarchically structured data. Interactions between activities and contexts were explored.ResultsParticipants were highly active: 98.5% met physical activity guidelines. Sedentary activities were negatively associated with sense of purpose, especially when indoors. Social sedentary activities (e.g. visiting friends and family) were, however, positively associated with feelings of happiness. Active, social outdoor activities were positively associated with both outcomes. Less sedentary participants experienced higher happiness and sense of purpose during all their activities: each 1 percentage point increase in percentage time sedentary was associated with a reduction of 2.78-points on the happiness scale and 3.34 on the purpose scale (p <0.05). Conclusions Context is important for happiness and purpose, with social and outdoor activities likely to have the widest appeal for older adults. The study needs to be replicated in larger and more representative samples of older adults.