Date of Degree
PhD (Doctor of Philosophy)
Health and Sport Studies
Kathleen F. Janz
Osteoporosis (OP) is a disease characterized by low bone mass and structural breakdown of the skeleton. The disease may be prevented through weight-bearing, moderate to vigorous physical activity (MVPA), which is important for peri- and postmenopausal women who are at great risk for OP. However, most women do not participate in activity according to guidelines, which can negatively impact bone health. A better understanding of multidimensional factors that influence MVPA may help inform physical activity interventions aiming for OP prevention. The purpose of this study was to utilize social cognitive theory (SCT) to understand the associations between social cognitive factors and MVPA among peri- and postmenopausal women.
Eighty-seven peri- and postmenopausal women (aged 43 to 65) completed this study. Participants completed demographic, health, calcium, and SCT questionnaires. SCT variables assessed included task self-efficacy (SET) and barrier self-efficacy (SEB), perceived social support from friends (SSFR) and family (SSFA), and perceived access to facilities (ACF) and home equipment (ACH). Participants wore an NL-1000 pedometer for one week to assess total steps per day and minutes spent in MVPA. Past year MVPA, past week leisure MVPA, and past week occupational/ transport MVPA were assessed with the Modifiable Activity Questionnaire.
Stepwise regression analysis was used to identify the direct relationships between cognitive variables and each of the physical activity outcome measures. Moderation-mediation analysis was conducted to determine if significant interaction effects or confounding effects existed between social cognitive variables and each physical activity variable. Age, income, BMI, and highest level of education were controlled for in all analyses.
Results showed significant relationships between social cognitive factors and each physical activity outcome, supporting the use of such variables for understanding physical activity behavior in peri- and postmenopausal women. For steps per day and MVPA minutes per day, 32% and 26% of the variance in activity was explained. For past year MVPA, past week leisure MVPA, and occupational/ transport MVPA, 39%, 26%, and 27% of the variance in activity was explained, respectively. The combination of variables entering the models was different for each physical activity outcome, but overall, SEB consistently emerged as the most prominent factor. Moderation analyses revealed a three way interaction effect between SEB, SSFR, and ACF for steps per day, and two-way interaction effects between SEB and SSFR for past year MVPA and past week leisure MVPA. Mediation analysis indicated SSFA confounded the relationship between SEB and past year MVPA.
Results of this study indicate social cognitive factors are directly and indirectly associated with total and MVPA in peri- and postmenopausal women. These relationships should be considered when aiming to develop physical activity intervention programs for prevention of OP in peri- and postmenopausal populations.
Copyright 2010 Heather Chi Medema-Johnson
Medema-Johnson, Heather Chi. "Social cognitive factors associated with moderate to vigorous physical activity in perimenopausal and postmenopausal women." dissertation, University of Iowa, 2010.