- To elucidate downstream effects of the intervention in terms of mental health (i.e., depressive symptoms, chronic stress) and physical health outcomes (i.e., inflammatory status) In line with the Roybal Center Aim 1, the current study explicitly targets a population of sedentary middle-aged and older adults who unsuccessfully attempted to increase physical activity. Pressure to change behavior will in many cases stem from health decrements. Furthermore, participants will be recruited from the Waltham community, which will allow targeted advertisement to ensure a diverse sample in terms of socioeconomic background as well as ethnicity. Lastly, only participants who cannot walk for stretches of several minutes without pain will be excluded, allowing individuals in early stages of disability to participate. Using a stress framework to develop the current intervention and assessing psychological, social, and biological correlates will contribute to Roybal Center Aim 2, as the findings will advance theory and empirical findings on behavior change processes and mechanism. Lastly, the current study addresses Roybal Center Aim 3, as knowledge gained from the current study will facilitate larger-scale physical activity interventions expected to improve health and quality of life of older adults.