Individually tailored physical activity intervention for Latina adolescents: Ninas Saludables - Abstract
Latina adolescents report low levels of physical activity, with only 3% meeting national physical activity
guidelines, and are at high lifetime risk for conditions related to inactivity, such as obesity, metabolic syndrome,
and diabetes. Interventions grounded in sound psychosocial theory and leveraging growing technology use in
Latina adolescents are needed to reverse patterns of inactivity, establish healthy lifetime habits and reduce
widening disparities. Our research team has developed and tested individually tailored web-based
interventions to increase moderate-to-vigorous physical activity (MVPA), which significantly increased MVPA in
Latina adults. In our recent pilot study (R03NR014329), we adapted this intervention based on formative
interviews to make it appropriate for Latina adolescents and tested it in a single-arm pilot trial (N=21). After 12
weeks, retention was high (90.5%) and self-reported MVPA increased from 24.7(26.11) minutes/week at
baseline to 79.4(46.8) at follow up (p<0.001), suggesting good potential efficacy. In closeout interviews, girls
expressed a preference to increase audio-video components of the website and to incorporate other mobile-
health technologies, such as texting, smartphone apps, social networks, and wearables. Thus, the aim of this
study is to conduct a randomized controlled trial (N=200) of an individually tailored, theory-based, multi-
technology intervention to increase MVPA in Latina adolescents. The 12-month intervention will comprise a
counseling session to teach behavior change techniques, an interactive multimedia website with individually
tailored content, a wearable tracker and smartphone app to reinforce behavior change techniques, connection
to an Instagram account reinforcing web content, and automated text messages to guide continued goal
setting. Participants will be randomly assigned to receive the intervention or only a wearable tracker. Activity
will be measured at baseline, six-months (primary outcome) and 12 months using well-established MVPA
measures (accelerometers and the 7-Day Physical Activity Recall Interview). We hypothesize that those
randomized to receive the intervention will show significantly greater increases in MVPA at six months than
those in the control group. We will also evaluate whether changes in MVPA are mediated by changes in
targeted psychosocial constructs (e.g. self-efficacy, social support), and whether intervention effects are
moderated by baseline personal and environmental variables (e.g. age, BMI, neighborhood environment).
Costs to deliver the intervention (e.g. staff time, materials, overhead) will be tracked to evaluate costs and cost-
effectiveness of both study arms, and we will evaluate the effects of contact time out outcomes. We will also
explore trajectories of daily activity in both the intervention and control groups using continuous data from
wearable trackers. The proposed study will promote a critical preventive health behavior, physical activity, in
Latina adolescents using technologies that are pervasive in this high risk population and highly scalable, laying
the groundwork for cost-effective, broad reaching interventions with great potential for public health impact.
