Reliability and validity of expected outcomes and barriers for habitual physical activity.
We conducted two studies to examine the reliability and validity of self-report scales for assessing outcome-expectancy values and perceived barriers for participating in regular physical activity. In study one with college students (N = 243), independent and reliable psychometric factors were identified as outcome-expectancy values (psychologic, body image, and health) and perceived barriers (time, effort, and obstacles). alpha internal consistency coefficients ranged from .47 to .78, and test-retest stability correlations were .66 to .89. In prospective analyses, subscales significantly predicted supervised running (R2 = .27) and free-living physical activity estimated by seven-day recall at two-, five-, and nine-week intervals (R2 ranged from .13 to .24). In study two with employees at CONOCO World Headquarters (N = 968), similar independent scales were derived for outcome-expectancy values (psychologic, body image/health, competition, fun, and social) and perceived barriers (time, effort, obstacles, and limiting health). alpha internal consistencies ranged from .66 to .85. In cross-sectional analyses the scales combined with sociodemographic factors were significantly correlated with membership (R2 = .18) and participation (R2 = .17) in the on-site health and fitness program. In each instance outcome-expectancy values and perceived barriers explained variance in physical activity not accounted for by sociodemographics (R2 values increased .12). Membership in health and fitness programs outside the work site was also predicted (R2 = .07) by the scales. The scales provide a reliable and valid measurement technology that can be implemented with college or work site populations. Existing social psychology theories of behavior that include outcome-expectancy values or perceived barriers can now be examined as explanations for the adoption and maintenance of a physical activity program.