Physical Activity and Quality of Life—The Complementary Influence of Self-Efficacy for Physical Activity and Mental Health Difficulties Raheem J. Paxton & Robert W. Motl & Alison Aylward & Claudio R. Nigg Received: 24 August 2009 / Accepted: 23 February 2010 / Published online: 7 May 2010 # International Society of Behavioral Medicine 2010 Abstract Background Studies proposed that the physical activity and quality of life (QoL) relationship may not be entirely direct but mediated through other variables; however, few studies have examined these relationships in diverse population’ s older adults. Purpose This study aims to examine the roles of self- efficacy and mental health difficulties in the physical activity and QoL relationship and to determine if demo- graphic characteristics alter these relationships. Methods One hundred ninety-six older adults completed measures of physical activity, self-efficacy, mental health difficulties, and QoL. Two-multilevel structural models were tested to determine the relationship between physical activity and QoL. Results Both structural models suggested that the relation- ship between physical activity and QoL is indirect, but the models were not significantly different. In model 1, we observed a positive linear relationship between physical activity and self-efficacy. In turn, self-efficacy was nega- tively associated with poor mental health difficulties and positively associated with QoL. Mental health difficulties were also negatively associated with QoL. In model 2, physical activity was positively associated with self- efficacy and negatively associated with mental health difficulties; in turn, self-efficacy was positively associated with QoL, whereas mental health difficulties were nega- tively associated with QoL. Conclusions Overall, our findings suggest that self-efficacy and mental health have intermediary roles in the relation- ship between physical activity and QoL in a diverse sample of older adults. Prospective studies are needed to determine whether self-efficacy and mental health difficulties are complementary or one or the other accounts for more variance in the relationship between physical activity and QoL. Keywords Aging . Diverse . Mental health . Physical activity . Quality of life . Self-efficacy Introduction The population of older adults in the USA is increasing substantially [1]. Of interest are older adult communities with longer life expectancies, such as the residents of Hawaii. These older adults tend to live 3 years longer (79.8 years versus 76.9 years) than other populations of older adults across the USA and are much more racially and ethnically diverse [2, 3]. As Hawaiian residents are living longer, there is a concern about maintaining their quality of life (QoL). Several studies conducted among older adult communities suggest that participation is regular and sustained physical activity is associated with improved QoL in later years of life [4–6]. Studies conducted in diverse populations have confirmed these relationships as well. For example, two recent cross-sectional studies observed that physical activity R. J. Paxton (*) The Center for Research on Minority Health, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA e-mail: rjpaxton@mdanderson.org R. W. Motl University of Illinois Champaign–Urbana, Urbana, IL, USA A. Aylward : C. R. Nigg University of Hawaii (Manoa)—School of Public Health, Honolulu, CDP, HI, USA Int.J. Behav. Med. (2010) 17:255–263 DOI 10.1007/s12529-010-9086-9