Abstract Risks for cardiovascular disease (CVD) substantially increase for women during midlife (ages 40-60). Increasing physical activity (PA) during midlife can mitigate these risks and there is a critical need for research that can reduce barriers to engagement in this population. PA measurement reactivity, or a change in PA engagement in response to the introduction of PA measurement, may bias the objective assessment of PA that is critical to evaluating PA promotion efforts. Specifically, PA measurement reactivity could inflate estimates of PA early in a monitoring period and lead to incorrect conclusions about PA engagement among at-risk groups such as women in midlife. At present, however, evidence supporting PA measurement reactivity as a key confound in PA research is mixed, including preliminary evidence from the PI’s K23 award. The proposed study is designed to address three key limitations of existing work: (1) emphasis on children or healthy, young adults with low risk for CVD, (2) lack of consistency with respect to the definition of reactivity and the PA outcome(s) most likely to be affected (e.g., steps vs. minutes of moderate-to-vigorous activity [MVPA] per day), and (3) lack of attention to the contexts whereby reactivity may be most influential (e.g., study designs, individual differences between participants). In the proposed R03, we will use 7 existing datasets from the PI’s K23 activities, mentors’ clinical trials, and publicly available databases to examine PA measurement reactivity among women in midlife with elevated CVD risk (e.g., obesity, hypertension; N = 800). Using a coordinated analysis approach, we will employ multilevel modeling techniques to achieve the following aims: (1) To characterize midlife women’s PA measurement reactivity across four PA outcomes: steps, minutes of light activity, minutes of MVPA, and minutes spent in sedentary behavior, (2) To determine whether the presence or extent of measurement reactivity differ based on study characteristics such as research design (i.e., observation only vs. PA assessment pre-intervention) and PA monitoring procedures (i.e., research-grade accelerometers vs. commercially available wearables), and (3) To determine whether the presence or extent of measurement reactivity differ based on medical or psychological characteristics, including BMI, motivation to engage in PA, and depressive symptoms. This work will generate preliminary data to identify circumstances associated with problematic levels of PA measurement reactivity among women in midlife and potential targets for reducing it in an at-risk group. This R03 thus represents an innovative extension of the PI’s K23 program that will leverage institutional resources and insights to date and contribute to the scientific rigor of research in the fields of PA measurement and intervention. Consequently, this work will support the PI’s development as a leading independent investigator, focused on promoting PA to reduce CVD risk in at-risk populations.

Project Narrative Women in midlife (ages 40-60) are at unique risk for cardiovascular disease, in part due to decreases in physical activity, and there is a critical need for research that can reduce barriers to physical activity engagement. Reactivity to physical activity measurement (i.e., inflated physical activity engagement in response to the introduction of monitoring) poses a threat to these efforts, as it may bias activity estimates from monitoring devices, though it has not been examined in at-risk populations such as women in midlife. The proposed study will contribute to the scientific rigor of work in this area by estimating the influence of and identifying study and participant characteristics associated with reactivity responses, toward the goal of developing best practice recommendations for mitigating its effects in at- risk groups such as women in midlife.