ACKNOWLEDGMENTS BACKGROUND Funded by: American Cancer Society MRSGT CPPB (Dunton, PI) and National Cancer Institute R01-CA (Pentz, PI). Contact information: Yue Liao, MPH, University of Southern California N. Soto Street, Institute of Preventive Research Alhambra, CA adult residents from San Bernardino County, California. 72% females and 30% Hispanic. Ages 27 – 73 (M = 40). 62% were overweight/obese. PARTICIPANTS Intention, self-efficacy, and outcome expectancy are recognized as important cognitive determinants for physical activity (PA). However, few studies have examined the near-time (i.e., within a few hours) effects of these cognitive determinants on PA partially due to the difficulty in assessing intention, self-efficacy, and outcome expectancy in real-time under naturalistic conditions. RESEARCH OBJECTIVE The current study used Ecological Momentary Assessment (EMA) to 1)examine whether intention, self-efficacy, and outcome expectancy predict physical activity levels in the next 2 hours during the course of adults’ everyday life; and 2)determine which of the three cognitive factors is a stronger predictor of the subsequent physical activity levels. Participants were monitored for 4 days (Saturday – Tuesday) wearing a mobile phone (T-Mobile Shadow) and an accelerometer (Actigraph GT2M) during their waking hours. Electronic surveys delivered by mobile phones assessed intention, self-efficacy (2 questions), and outcome expectancy (4 questions) in physical activity 4 times a day at random intervals throughout the day. Physical activity level was measured by accelerometer and converted to moderate-to-vigorous physical activity (MVPA) minutes. METHODS RESULTS CONCLUSIONS Adults who had greater intention and self-efficacy for physical activity relative to their usual level engaged in more MVPA minutes in the following 2-hr period. Ecological Momentary Interventions might consider using strategies to increase adults’ self-efficacy state to promote physical activity level on a within-day basis. Future studies could examine what other factors moderate the effects of cognitive determinants on subsequent physical activity (e.g., assessing stage of change, mood). A follow-up analysis including both intention and self-efficacy in the multilevel model showed that only self-efficacy remained significant in predicting subsequent total MVPA minutes (beta coef. = 1.74, p =.04), suggesting that self-efficacy might be a stronger cognitive determinant than intention and outcome expectancy. Greater intention and self-efficacy relative to one’s usual (average) level were associated with more total MVPA minutes in the following 2-hour period (p’s<.05, see Figure 3 & Figure 4). Outcome expectancy was not related to the subsequent MVPA minutes. Figure 1. Screen shots of sample EMA questions Total minutes in MVPA were calculated within the 2 hours after the intention, self-efficacy, and outcome expectancy questions were answered by participants. Three multilevel models controlling for clusters within individuals were fit using prompt-level intention/self- efficacy/outcome expectancy as the predictor, separately, and total MVPA minutes in the next 2 hours as the outcome. All models controlled for age, gender, weight status, household income, weekend/weekday, and individuals’ overall average daily intention/self-efficacy/outcome expectancy scores. 9:30am9:30-11:30am12:50pm12:50-2:50pm4:35pm4:35-6:35pm7:20pm7:20-9:20pm EMA Prompt EMA Prompt EMA Prompt EMA Prompt Total MVPA Minutes Figure 2. Illustration of time-matched EMA and activity assessment Intention MVPA Minutes beta coef. = 1.13 Self-Efficacy MVPA Minutes beta coef. = 1.01 Figure 3. Prompt-level intention predicting total MVPA minutes in the following 2-hour period Figure 4. Prompt-level self-efficacy predicting total MVPA minutes in the following 2-hour period