Laboratory Model for Relapse to Sedentary Behavior

Physical inactivity is a key risk factor for noncommunicable illnesses such as cancer and cardiovascular disease (CVD)-the two leading causes of death in West Virginia. Physical inactivity is fundamentally a behavior problem, and there is a growing body of research supporting the use of incentive-based interventions to increase physical activity. In such interventions, participants earn incentives such as money, tokens or points, entries into prize drawings, or fitness-related commodities (e.g., gym memberships) by meeting defined goals (e.g., daily steps, energy expenditure, fitness classes).

A crucial feature of any successful intervention is sustained behavior-change following the removal or decrease in supports. However, most evaluations of incentive-based interventions are completed on a short-term scale (4 to 12 weeks) and often fail to provide data on follow-up. The studies that follow participants after the discontinuation of incentives often show relapse to sedentary behavior following intervention. Similar relapse is common following incentive-based interventions for other health-related behavior. Laboratory models of relapse prevention have informed treatment for these other forms of health-related behavior, but they have yet to be extended to interventions addressing sedentary behavior.

The investigators' long-term goal is to develop practical interventions that sustain increases in physical activity and thereby decrease a significant risk factor for disease (e.g., cancer, diabetes). The overall objective of the proposed project is to evaluate a brief laboratory model of relapse that is based on basic behavioral research grounded in Behavioral Momentum Theory. The central hypothesis is that incentives in the brief model will produce the expected increases in physical activity relative to no-incentive controls, but that these gains will be rapidly lost when the incentives are discontinued. This hypothesis is based other laboratory-based models of relapse (e.g., illicit drug use and challenging behavior), which mirrored outcomes of, and led to advances in clinical, treatment. The rationale for this project is that a laboratory model of relapse of sedentary behavior will inform future translational research and lead to large-scale clinical trials of incentives to improve physical activity that result in large, immediate behavioral change and that minimize subsequent relapse.

The central hypothesis is that incentives in the brief model will produce the expected increases in physical activity relative to no-incentive controls, but that these gains will be rapidly lost when the incentives are discontinued. These outcomes would suggest that the brief model produces outcomes similar to those obtained in more extended clinical treatment.

Approach The anticipated number of participants is 30 individuals (age 18-74). Participants will attend a single 90-min laboratory appointment. The laboratory space will be equipped with a treadmill, comfortable seating, and leisure activities. A licensed nurse will screen participants to ensure they are healthy enough to engage in physical activity and will remain present for the duration of participation to provide medical assistance in the unlikely event that it is needed. Block randomization will be used to assign participants to one of three groups (one experimental and two control groups). All groups will experience three phases of the study. Opportunities for sedentary leisure and physical activities will be continuously available throughout all phases. The first phase will mimic pre-intervention conditions; there will be a variety of activities available. No incentives for engaging in physical activity will be provided, although such activities will be available. For the Relapse (experimental) Group, the second phase will mimic an incentive-based intervention in which participants can earn monetary incentives for engaging in physical activity. Then, during the third phase, the incentives will be discontinued the Fatigue Control group will experience the same conditions for Phase 1 and 2, but they will continue to earn incentives during Phase 3. The No-Incentive Control group will not earn incentives during any phase to control for the possibility that participants will engage in some physical activity in the absence of incentives.

Participants will wear a heart rate monitor throughout the study to provide real-time data on activity level and trained research assistants will use software to score time-stamped duration of engagement in available activities (e.g., walking, sitting). A one-way ANOVA will be used to compare mean durations of physical activity across groups. A power analysis[23] shows that including 30 participants (10 in each group) will provide sufficient power to detect an effect size of 0.8 at an alpha of 0.05. Additionally, the investigators will use the heart rate data for preliminary analyses of mediation and moderation effects.