Delivered by Publishing Technology to: Chinese University of Hong Kong IP: 174.20.130.164 on: Sun, 14 Feb 2016 10:18:09 Copyright (c) PNG Publications. All rights reserved. Am J Health Behav 2003;27(5):493-507 493 Social Support and Social Norms: Do Both Contribute to Predicting Leisure-time Exercise? Morris A. Okun, PhD; Linda Ruehlman, PhD; Paul Karoly, PhD; Rafer Lutz, PhD Chris Fairholme, BS; Rachel Schaub, BS Morris A. Okun, Professor; Paul Karoly, Pro- fessor; Chris Fairholme, Research Assistant; Rachel Schaub, Research Assistant, Department of Psychology, Arizona State University, Tempe, AZ. Linda Ruehlman, Director of Research, Con- sultants in Behavioral Research, Tempe, AZ. Rafer Lutz, Assistant Professor, Department of Health, Human Performance, and Recreation, Baylor University, Waco, TX. Address correspondence to Dr. Okun, Depart- ment of Psychology, Arizona State University, Tempe, AZ 85287-1104. E-mail: d.rmorris@asu.edu Objective: To clarify the contri- bution of social support and social norms to exercise behavior. Meth- ods: A sample of 363 college stu- dents completed a questionnaire that assessed social support and social negativity from friends, de- scriptive and injunctive social norms related to friends, perceived behavioral control, attitude, inten- tion, and leisure-time exercise. Results: Esteem social support was the strongest predictor of total and strenuous leisure-time exercise (P<.001), and descriptive norm was a significant (P<.01) predictor of strenuous leisure-time exercise. Conclusion: Social support and so- cial norms contribute indepen- dently to our understanding of varia- tion in the frequency of strenuous leisure-time exercise. Key words: exercise, norms, planned behavior, social negativ- ity, and social support Am J Health Behav 2003;27(5):493-507 T he benefits of physical activity have been documented for many health outcomes, including longevity, func- tional health, and psychological well-be- ing. 1-3 These findings have provided the impetus for national and international organizations to issue statements calling for the promotion of physical activity. 4-5 Although surveys suggest that physical activity in developed countries has in- creased over the past 10 years, 6 the ma- jority of the US adult population report little or no exercise of even low to moder- ate intensity. 7 Despite being aware of the benefits of exercise, 8 many people are unable to sustain participation in pro- grams of exercise. 9 Several motivational theories have been employed to examine this disjunc- ture between awareness of the benefits of exercise and low levels of engagement in physical activity. 10 One of these theo- ries—the theory of planned behavior 11 — has demonstrated considerable predic- tive utility in accounting for variance in exercise behavior. 12 Nevertheless, one of this theory's main explanatory constructs, subjective norm, has not performed well in studies where the theory of planned behavior has been applied to the exercise domain. 13 In contrast, researchers have found that social support is a determinant of exercise. 14 Biddle and Mutrie 10 called for additional research to address the discrepancy between the predictive power of social support and social norms in ac-