Mediating variable framework in physical activity interventions. How are we doing? How might we do better?

Environmental correlates of physical activity in a sample of Belgian adults

PURPOSE

This study investigated the variance in sitting, walking, and moderate and vigorous physical activity explained by neighborhood design and recreational environmental variables above and beyond the variance accounted for by individual demographic variables.

DESIGN

Cross-sectional analyses of self-reported survey data.

SETTING

A random sample of inhabitants of Ghent, Belgium, aged 18-65 years, was drawn.

SUBJECTS

Five hundred twenty-one adults completed questionnaires (52.1% response rate). The average age of the sample was 41 years, and 48.2% were female.

MEASURES

A questionnaire developed to assess neighborhood design and recreational environmental variables with a total of 81 items was administered. The environmental questionnaire showed acceptable to good reliability and acceptable validity. The previously validated International Physical Activity Questionnaire (IPAQ) was used to quantify physical activity in the past 7 days. Additional demographic information was also obtained.

RESULTS

Regression analyses showed that environmental variables were related to all types of physical activity in both sexes. However, the range of variance explained by the models including demographic and environmental variables was low, only 5% to 13%. Minutes of walking and of moderate-intensity activity were related to quality of sidewalks and accessibility of shopping and public transportation. Vigorous physical activity was related to presence of activity supplies in the home and number of convenient activity facilities outside the home.

CONCLUSIONS

Both neighborhood design and recreational environment variables had small but significant associations with multiple types of physical activity in a sample of Belgian adults.

Couch kids: correlates of television viewing among youth

The purpose of this study was to review the published empirical correlates of television/video viewing among youth (2 to 18 years). A descriptive semi-quantitative review was conducted based on 68 primary studies. Variables consistently associated with TV/video viewing were ethnicity (non-white +), parent income (-), parent education (-), body weight (+), between meal snacking (+), number of parents in the house (-), parents TV viewing habits (+), weekend (+) and having a TV in the bedroom (+). Variables consistently unrelated to TV/video viewing were sex, other indicators of socio-economic status, body fatness, cholesterol levels, aerobic fitness, strength, other indicators of fitness, self-perceptions, emotional support, physical activity, other diet variables, and being an only child. Few modifiable correlates have been identified. Further research should aim to identify modifiable correlates of TV/video viewing if interventions are to be successfully tailored to reduce this aspect of inactivity among youth.

Obesity in American-Indian children: prevalence, consequences, and prevention

BACKGROUND

American Indians of all ages and both sexes have a high prevalence of obesity. The health risks associated with obesity are numerous and include Type 2 diabetes mellitus, hypertension, dyslipidemia, and respiratory problems. Obesity has become a major health problem in American Indians only in the past few generations and it is believed to be associated with the relative abundance of high-fat, high-calorie foods and the rapid change from active to sedentary lifestyles.

METHODS

The authors reviewed selected literature on prevalence of obesity in American-Indian children, and health consequences of obesity.

RESULTS

Obesity is now one of the most serious public health problems facing American-Indian children, and it has grave implications for the immediate and long-term health of American-Indian youth. Unless this pattern is reversed, American-Indian populations will be burdened by an increased incidence of chronic diseases. Intervention studies are urgently needed in American-Indian communities to develop and test effective strategies for obesity prevention and treatment.

CONCLUSIONS

To be effective, educational and environmental interventions must be developed with full participation of the American-Indian communities.

Groningen Active Living Model (GALM): stimulating physical activity in sedentary older adults; validation of the behavioral change model

BACKGROUND

A significant proportion of older adults in The Netherlands do not participate regularly in leisure-time physical activity. The Groningen Active Living Model (GALM) was developed to change this situation for the better. Longitudinal results of the validation of the GALM behavioral change model are presented.

METHODS

We obtained data on potentially mediating variables of physical activity behavior change (self-efficacy, social support, perceived fitness, and enjoyment) from 96 participants in a prospective study during the 18 months the GALM strategy lasted.

RESULTS

Prospective analyses revealed significant differences in several potentially mediating variables, although some of these differences were contrary to our hypothesis. Discriminant analysis resulted in canonical correlations of 0.50 after 6 months and 0.66 after 18 months of program participation between adherers and nonadherers, respectively; 73.8 and 80.0% of the subjects were classified correctly.

CONCLUSIONS

Based on the results, it can be concluded that we partially succeeded in manipulating the potentially mediating variables by means of our GALM strategy. Several mediating variables were identified that reliably discriminated long-term adherers from nonadherers, expanding the generalizability of social cognitive theory-driven variables to a Dutch population.

Developing an empirical typology for regular exercise

BACKGROUND

Tailored interventions require the identification of distinct homogenous subgroups that will benefit from different intervention materials. One way to identify such subgroups is to use cluster analysis to identify an empirical typology.

METHODS

A sample of 346 adults completed surveys through a telephone interview that included questions related to participating in regular exercise. The three variables used in the cluster analysis were the Pros of Exercise, the Cons of Exercise, and Exercise Self-Efficacy.

RESULTS

Six resulting clusters were labeled Disengaged, Immotive, Relapse Risk, Early Action, Maintainers, and Habituated. A series of analyses tested the internal and external validity of the typology. The internal validity test revealed that four of the clusters demonstrated high stability and replicability, while the Relapse Risk and Early Action clusters were less stable. Differences among clusters on self-reported exercise behavior and a strong association with stage of change for regular exercise provided external validity evidence of the typology.

CONCLUSIONS

The resulting typology reflects a range of motivational patterns that are likely to be responsive to different types of messages and strategies regarding adoption and maintenance of regular exercise. The typology also generates a number of hypotheses about the identified clusters that can be empirically tested in further studies.

Evaluating a model of parental influence on youth physical activity

OBJECTIVE

To test a conceptual model linking parental physical activity orientations, parental support for physical activity, and children's self-efficacy perceptions with physical activity participation.

PARTICIPANTS AND SETTING

The sample consisted of 380 students in grades 7 through 12 (mean age, 14.0+/-1.6 years) and their parents. Data collection took place during the fall of 1996.

MAIN OUTCOME MEASURES

Parents completed a questionnaire assessing their physical activity habits, enjoyment of physical activity, beliefs regarding the importance of physical activity, and supportive behaviors for their child's physical activity. Students completed a 46-item inventory assessing physical activity during the previous 7 days and a 5-item physical activity self-efficacy scale. The model was tested via observed variable path analysis using structural equation modeling techniques (AMOS 4.0).

RESULTS

An initial model, in which parent physical activity orientations predicted child physical activity via parental support and child self-efficacy, did not provide an acceptable fit to the data. Inclusion of a direct path from parental support to child physical activity and deletion of a nonsignificant path from parental physical activity to child physical activity significantly improved model fit. Standardized path coefficients for the revised model ranged from 0.17 to 0.24, and all were significant at the p<0.0001 level.

CONCLUSIONS

Parental support was an important correlate of youth physical activity, acting directly or indirectly through its influence on self-efficacy. Physical activity interventions targeted at youth should include and evaluate the efficacy of individual-level and community-level strategies to increase parents' capacity to provide instrumental and motivational support for their children's physical activity.

Maintaining regular physical activity in women: evidence to date

Physical activity is well established as a primary health promotion and cardiovascular disease prevention behavior, yet over 60% of the population does not participate in regular physical activity. Maintenance of regular physical activity is a complex behavior influenced by variables from several domains. This review includes studies of the relationship between physical activity in women and psychological, social environmental, demographic, physiologic, health status, and physical activity variables. A key issue in physical activity research is development of interventions for maintaining a physically active lifestyle. Interventions for maintenance of regular physical activity that have a strong theoretical basis will be beneficial to women in primary care settings, occupational settings, wellness centers as well as public health departments and other organizations that address the needs of women.

Neighborhood-based differences in physical activity: an environment scale evaluation

OBJECTIVES

This study evaluated a neighborhood environment survey and compared the physical activity and weight status of the residents in 2 neighborhoods.

METHODS

On 2 occasions, 107 adults from neighborhoods with differing "walkability" were selected to complete a survey on their neighborhood environment. Physical activity was assessed by self-report and by accelerometer; height and weight were assessed by self-report.

RESULTS

Neighborhood environment characteristics had moderate to high test-retest reliabilities. Residents of high-walkability neighborhoods reported higher residential density, land use mix, street connectivity, aesthetics, and safety. They had more than 70 more minutes of physical activity and had lower obesity prevalence (adjusted for individual demographics) than did residents of low-walkability neighborhoods.

CONCLUSIONS

The reliability and validity of self-reported neighborhood environment subscales were supported. Neighborhood environment was associated with physical activity and overweight prevalence.

Predicting long-term maintenance of physical activity in older adults

BACKGROUND

Considerable research has established that self-efficacy is a consistent correlate of physical activity. Additional factors, such as exercise-induced affect, social support, and value judgments, have also been identified as having the potential to influence adherence to activity. This study examined the utility of such variables in predicting the long-term exercise behavior of older adults.

METHOD

In the context of a 6-month randomized controlled trial with an 18-month follow-up, we tested the extent to which adherence during the trial, affective responses to exercise, exercise value, and social support from the exercise group had either a direct or indirect effect through the mediation of exercise self-efficacy on physical activity levels at 6- and 18-month follow-up in a sample (N=174) of older adults (M age, 66 years). Structural equation modeling tested several models of exercise prediction.

RESULTS

The best fitting model indicated significant paths from social support, affect, and exercise frequency to efficacy at the end of the program. Efficacy, in turn, was related to physical activity at 6- and 18-month follow-up. The model accounted for 40% of the variance in 18-month activity levels.

CONCLUSION

This prospective study provides support for the inclusion of social cognitive variables in models of exercise adherence and highlights the pivotal role of self-efficacy in long-term exercise behavior. Subsequent trials are called for to replicate and extend these findings.

Exercise-related goals and self-efficacy as correlates of aquatic exercise in individuals with arthritis

OBJECTIVE

To examine whether aquatic exercise-related goals, task self-efficacy, and scheduling self-efficacy are predictive of aquatic exercise attendance in individuals with arthritis. A secondary objective was to determine whether high attendees differed from low attendees on goals and self-efficacy.

METHODS

The sample comprised 216 adults with arthritis (mean age 69.21 years). Measures included exercise-related goal difficulty and specificity, task and scheduling self-efficacy, and 8-week aquatic exercise attendance.

RESULTS

Results of a multiple hierarchical regression analysis were significant (P < 0.01). Goal difficulty, specificity, and task self-efficacy were independent predictors of attendance (P < 0.05). A significant multivariate analysis of variance (P < 0.01) indicated that high attendees had higher task and scheduling self-efficacy and lower goal difficulty than did low attendees (P < 0.05).

CONCLUSION

Support for the importance of exercise-related goal setting and self-efficacy was demonstrated. Implications pertain to the design of interventions to impact aquatic exercise.

Using social cognitive theory to explain discretionary, "leisure-time" physical exercise among high school students

PURPOSE

To examine whether knowledge of high school students' actions of self-regulation, and perceptions of self-efficacy to overcome exercise barriers, social situation, and outcome expectation will predict non-school related moderate and vigorous physical exercise.

METHODS

High school students enrolled in introductory Physical Education courses completed questionnaires that targeted selected Social Cognitive Theory variables. They also self-reported their typical "leisure-time" exercise participation using a standardized questionnaire. Bivariate correlation statistic and hierarchical regression were conducted on reports of moderate and vigorous exercise frequency.

RESULTS

Each predictor variable was significantly associated with measures of moderate and vigorous exercise frequency. All predictor variables were significant in the final regression model used to explain vigorous exercise. After controlling for the effects of gender, the psychosocial variables explained 29% of variance in vigorous exercise frequency. Three of four predictor variables were significant in the final regression equation used to explain moderate exercise. The final regression equation accounted for 11% of variance in moderate exercise frequency.

CONCLUSIONS

Professionals who attempt to increase the prevalence of physical exercise through educational methods should focus on the psychosocial variables utilized in this study.

A longitudinal study of the impact of childhood and adolescent physical activity experiences on adult physical activity perceptions and behaviors

The authors describe the influence of childhood and adolescent physical activity on adult physical activity attitudes and behaviors. They conducted one-on-one, semistructured, indepth interviews with 16 men and 15 women from a longitudinal growth and development study and a follow-up investigation 25 years later. They used thematic analyses to analyze the data. Three themes emerged from the men's interviews: significant others, size and maturation, and physical ability, with clear distinctions among the active, average, and inactive men. The themes transitions, body image concerns, and significant others influenced the active, average, and inactive women. Specific relationships, circumstances, and attitudes formed in childhood and adolescence influenced adult physical activity predilection and behaviors.

Evaluation of a community-based intervention to promote physical activity in youth: lessons from Active Winners

PURPOSE

To test the effects of a community-based physical activity intervention designed to increase physical activity and to conduct an extensive process evaluation of the intervention.

DESIGN

Quasi-experimental.

SETTING

Two rural communities in South Carolina. One community received the intervention, and the other served as the comparison.

SUBJECTS

Public school students who were in fifth grade at the start of the study (558 at baseline) were eligible to participate. A total of 436 students participated over the course of the study.

INTERVENTION

The intervention included after-school and summer physical activity programs and home, school, and community components designed to increase physical activity in youth. The intervention took place over an 18-month period.

MEASURES

Students reported after-school physical activity at three data collection points (prior to, during, and following the intervention) using the Previous Day Physical Activity Recall (PDPAR). They also completed a questionnaire designed to measure hypothesized psychosocial and environmental determinants of physical activity behavior. The process evaluation used meeting records, documentation of program activities, interviews, focus groups, and heart rate monitoring to evaluate the planning and implementation of the intervention.

RESULTS

There were no significant differences in the physical activity variables and few significant differences in the psychosocial variables between the intervention and comparison groups. The process evaluation indicated that the after-school and summer physical activity component of the intervention was implemented as planned, but because of resource and time limitations, the home, school, and community components were not implemented as planned.

CONCLUSIONS

The intervention did not have a significant effect on physical activity in the target population of children in the intervention community. This outcome is similar to that reported in other studies of community-based physical activity intervention.

Squire's Quest! Dietary outcome evaluation of a multimedia game

BACKGROUND

Fruit, juice, and vegetable (FJV) consumption among children is low. Innovative programs are needed to enable children to increase FJV intake. Psychoeducational multimedia permits the delivery of interventions as designed and capitalizes on known behavior change principles.

DESIGN

Elementary school was the unit of recruitment, assignment, and analysis. Twenty-six elementary schools were pair matched on size and percentage of free or reduced-price lunch, and randomly assigned to treatment or control groups. Data were collected just before and just after the program.

SETTING/PARTICIPANTS

All fourth-grade students in participating elementary schools were invited to participate. Data were collected on 1578 students. MAIN OUTCOME Servings of fruit, 100% juice, and vegetables consumed.

INTERVENTION

Squire's Quest! is a ten-session, psychoeducational, multimedia game delivered over 5 weeks, with each session lasting about 25 minutes. Based on social cognitive theory, educational activities attempted to increase preferences for FJV through multiple exposures and associating fun with their consumption, increase asking behaviors for FJV at home and while eating out, and increase skills in FJV preparation through making virtual recipes.

MEASURES

Four days of dietary intake were assessed before and after the intervention. Assessment was made by the Food Intake Recording Software System (FIRSSt), which conducts a multiple pass, 24-hour dietary intake interview directly with the children.

RESULTS

Children participating in Squire's Quest! increased their FJV consumption by 1.0 servings more than the children not receiving the program.

CONCLUSIONS

Psychoeducational multimedia games have the potential to substantially change dietary behavior. More research is warranted.

Social cognitive determinants of physical activity in young adults: a prospective structural equation analysis

This study used a prospective design to test a model of the relation between social cognitive variables and physical activity in a sample of 277 university students. Social support, self-efficacy, outcome expectations, and self-regulation were measured at baseline and used to predict physical activity 8 weeks later. Results of structural equation modeling indicated a good fit of the social cognitive model to the data. Within the model, self-efficacy had the greatest total effect on physical activity, mediated largely by self-regulation, which directly predicted physical activity. Social support indirectly predicted physical activity through its effect on self-efficacy. Outcome expectations had a small total effect on physical activity, which did not reach significance. The social cognitive model explained 55% of the variance observed in physical activity.

Tracking and explanation of physical activity in young adults over a 7-year period

Tracking and explaining physical activity in young adults was investigated in a 7-year longitudinal design. From a representative sample of 980 respondents at baseline (M age = 21 years), 172 respondents, comprising 18% of the original sample, completed psychosocial questionnaires and were interviewed at home to assess their level of physical activity at follow-up. Psychosocial variables were grouped into four groups: social variables, self-efficacy, perceived benefits, and perceived barriers. Drop-out analyses showed no major differences between the baseline and follow-up samples. The aims of the present study were: (a) to investigate tracking in physical activity and psychosocial determinants over a 7-year period, and (b) to examine baseline determinants and change in determinants in predicting physical activity change in men and women. No significant tracking of physical activity level was found for men. For women, moderate tracking scores were found for total energy expenditure and moderate-intensity energy expenditure (r = .34 and .41, respectively). There was higher tracking in psychosocial determinants than in physical activity. Relatively high tracking scores for perceived benefits and barriers suggest that cognitions related to physical activity are more stable than the behavior itself. Although baseline psychosocial variables were poor predictors of physical activity change, determinants'change scores accounted for 16-19% of the variance in physical activity in men and 7-24% in women. Significant predictors were different for men and women. Present results can inform the design of physical activity interventions for these populations.

Development and expert evaluation of "Moms on the Move," a physical activity intervention for WIC mothers. Women, Infants, and Children

The purpose of this descriptive study was to develop and evaluate "Moms on the Move," a provider-counseled physical activity intervention for mothers enrolled in the Women, Infants, and Children (WIC) program. The intervention was based on the Transtheoretical Model (TTM) of behavior change. The evaluation occurred in two stages. In the first stage, physical activity behavioral experts (n=4) evaluated the: (a) rationale for intervention components; (b) linkages between behavior change constructs, intervention activities, and study outcomes; (c) literature support for the TTM behavior change constructs; and (d) the intervention brochure. The expert evaluation tool was adapted from the "Educational Materials Review Form." Each item in the expert evaluation met the <or= 3.0 mean criterion for acceptability (range, 1.33-2.67). Revisions were made based on expert comments before stage 2. In the second stage, WIC mothers (n=5) evaluated the intervention brochure. The 9-item WIC mothers' evaluation tool was adapted from a simple tool for community members. In the second stage evaluation, the mean total score for the intervention brochure evaluation was 44.0 (SD=1.22), which met the a priori criterion to retain as is. Mean item responses ranged from 4.8 to 5.0 (5.0=great). This evaluation indicates that "Moms on the Move" is a promising physical activity intervention for WIC mothers, which should be implemented for efficacy testing.

Interventions to promote physical activity among African American women

The lack of routine physical activity among African American women places them at risk for negative health outcomes associated with inactivity. The number of studies focused on African American women has increased dramatically in the past decade. This review examined the intervention research literature testing strategies to increase activity among African American women. Eighteen studies with 1,623 subjects were retrieved. Diverse interventions, settings, and measures were reported. Common methodologic weaknesses included lack of randomization of subjects, single-group design, instruments without documented validity and reliability, significant attrition, and questionable timing of outcome variable measurement. Strategies to design and deliver culturally appropriate interventions are reviewed. Suggestions for future research, such as examining intragroup differences and communal resources, are provided.

Physical activity among ethnically diverse college students

The authors compared physical activity patterns among 874 Asian, 332 African, 1,101 White, and 529 Hispanic American college students aged 18 to 25 years. According to self-report responses, 46.7% of the sample did not engage in vigorous physical activity and 16.7% were physically inactive. Among women, ethnic-specific rates of physical inactivity were Asian, 28.1%; African, 23.5%; White, 17.4%; and Hispanic, 20.3%. For men, rates of inactivity were Asian 11.7%; African, 7.7%; White, 12.0%; and Hispanic, 13.8. Weight-training activity, youthful physical activity, and TV viewing accounted for a significant portion of the variance in physical activity levels (13.1% for women and 14.8% for men). The results of this study support the need for physical activity interventions for college students, particularly minorities.

Emerging measurement and statistical methods in physical activity research

Although many studies have attempted to identify mediators and moderators of changes in physical activity involvement, the literature is inconclusive regarding which variable(s) relate to physical activity behavior change. The Cooper 2001 Conference series dedicated a session to discussing measurement and statistical methods that could contribute to advancing this research agenda. This article focuses on four such methodologic approaches: qualitative; psychometric; latent-variable, structural equation modeling; and multilevel modeling. The article presents a brief overview of these methods and discusses potential advantages and limitations of using them.

Toward a better understanding of the influences on physical activity: the role of determinants, correlates, causal variables, mediators, moderators, and confounders

BACKGROUND

For research on physical activity interventions to progress systematically, the mechanisms of action must be studied. In doing so, the research methods and their associated concepts and terminology become more complex. It is particularly important to clearly distinguish among determinants, correlates, mediators, moderators, and confounder variables used in physical activity research. This article examines the factors that are correlated with and that may have a causal relationship to physical activity.

METHODS AND RESULTS

We propose that the term "correlate" be used, instead of "determinant," to describe statistical associations or correlations between measured variables and physical activity. Studies of the correlates of physical activity are reviewed. The findings of these studies can help to critique existing theories of health behavior change and can provide hypotheses to be tested in intervention studies from which it is possible to draw causal inferences. Mediator, moderator, and confounder variables can act to influence measured changes in physical activity. Intervening causal variables that are necessary to complete a cause-effect pathway between an intervention and physical activity are termed "mediators." The relationship between an intervention and physical activity behaviors may vary for different groups; the strata by which they vary are levels of "moderators" of the relationship. Other factors may distort or affect the observed relationships between program exposure and physical activity, and are known as "confounders."

CONCLUSIONS

Consistent use of terms and additional research on mediators and moderators of intervention effects will improve our ability to understand and influence physical activity.

Intervention-related cognitive versus social mediators of exercise adherence in the elderly

CONTEXT

Participation in regular physical activity is recognized as one of the most important health behaviors associated with the prevention of chronic disease and the promotion of health and well-being among the elderly. Although a number of cross-sectional studies have reported predictors of physical activity participation, few studies have assessed changes in intervention-related mediators associated with physical activity adherence in the elderly.

OBJECTIVE

The purpose of this study was to compare the relative abilities of cognitive mediating variables (i.e., self-efficacy beliefs and outcome expectancies/realizations) versus a social mediating variable (i.e., exercise-related social support) to examine mediators of a telephone-based, exercise-counseling intervention on exercise adherence during months 7 to 12 of an exercise intervention.

METHOD

Participants were 103 community-dwelling, healthy, sedentary, older adults (67 women and 36 men). Self-efficacy for exercise, outcome expectancies/realizations, and social support for exercise were assessed at baseline, 6 months, and 12 months. Participants received telephone-based exercise counseling to promote exercise adherence during the course of two 12-month exercise programs (i.e., aerobic/strength or flexibility exercises).

RESULTS

Changes in cognitive mediators (i.e., self-efficacy and fitness outcome realizations) were associated with 7- to 12-month exercise adherence while exercise-related social support was not.

CONCLUSION

Attention should be given to increasing confidence in the elderly to overcome barriers to exercise and achieve relevant fitness outcomes in exercise programs.

Comparing the relationships between different types of self-efficacy and physical activity in youth

A preliminary study was conducted to compare the relationships between different types of self-efficacy and youth physical activity. Two samples of sixth- and seventh-grade students (Sample 1: N= 57; Sample 2: N= 49) reported their confidence to be physically active (physical activity efficacy), to overcome barriers to physical activity (barriers efficacy), to ask others to be active with them (asking efficacy), and to find and create environments that support physical activity (environmental-change efficacy). Physical activity was measured by averaging three 24-hour recalls of physical activity. Regression analyses were used to test the relationships between the types of self-efficacy and youth physical activity. Compared with the other types of self-efficacy, environmental-change efficacy had the strongest relationship with youth physical activity. This suggests that strengthening young persons' belief in their ability to find and create environments that support physical activity might promote increases in their physical activity.

Theoretical approaches to the promotion of physical activity: forging a transdisciplinary paradigm

BACKGROUND

Research in the physical activity promotion arena has focused on the application of theoretical perspectives aimed primarily at personal levels of understanding and analysis. The investigation of such theories has provided some insights related to potentially useful mediators of physical activity behavior. However, to continue to expand this field, new perspectives on personal-level theories, in addition to the exploration of more macro-level conceptual perspectives, are required.

OBJECTIVE

The purpose of this article is to: (1) briefly review the current strengths and limitations of the personal-level, physical activity-theory literature; and (2) introduce concepts and perspectives from other fields, including the social-ecology and urban-planning fields, of potential relevance to the physical activity arena.

METHOD

We provide an overview of potentially relevant theoretical perspectives aimed at different levels of understanding and analysis, from the personal level through the broader-scale meso- and macro-environmental perspectives. In addition, we suggest initial steps to take in developing a transdisciplinary paradigm encompassing all such levels of analysis and investigation.

CONCLUSIONS

Given the scope of the physical inactivity epidemic facing the U.S. population currently and in the future, methods and approaches that integrate theory and concepts across a broader group of disciplines will be increasingly necessary.

Mediators of physical activity behavior change among women with young children

BACKGROUND

Women with children are less likely to engage in adequate physical activity (PA) than women without children. This study aimed to evaluate the efficacy of two strategies for promoting increased PA among mothers of preschool-aged children, and to explore the mediators of any resulting change in PA behavior.

DESIGN

Controlled intervention trial incorporating repeated data collection from 554 women, randomized to one of three experimental conditions. Intervention Group 1 served as a control, while women in Groups 2 and 3 were given print information about overcoming PA barriers. Women in Group 3 were also invited to discuss the development of local strategies for the promotion of PA among mothers of young children. The primary strategies included increasing partner support, social advocacy, and capacity building, and were implemented through collaboration among participants, researchers, and community organizations.

MAIN OUTCOME MEASURES

Adequate physical activity (PA), self-efficacy (SE) and partner support (PS).

RESULTS

Following the intervention, women in Group 3 were significantly more likely to meet guidelines for PA than controls (odds ratio [OR]=1.71, confidence interval [CI]=1.05-2.77)] after controlling for age and PA at baseline. After controlling for baseline PA, residualized change in SE (OR=1.86, CI=1.17-2.94) and PS (OR=2.29, CI=1.46-3.58) significantly predicted meeting guidelines. After controlling for residual change in PS and SE, the significant intervention effect was attenuated (Group 3 OR=1.40, CI=0.76-2.36), indicating that partner support and self-efficacy may be mediators of physical activity behavior change.

CONCLUSIONS

The findings indicate that community participation approaches that facilitate increased self-efficacy and partner support can be effective in increasing PA among mothers of young children.

Psychosocial mediators of physical activity behavior among adults and children

BACKGROUND

Researchers examining theory-based, physical activity (PA) interventions postulate that interventions are effective by changing theoretical constructs hypothesized to mediate the relationship between the intervention and PA behavior. Research indicates that PA interventions are effective for increasing PA behavior. However, whether effective interventions are due to predicted changes in theoretical constructs remains poorly understood.

METHODS

Studies that examined theoretical constructs (i.e., mediators) in PA interventions of adults or children, which used experimental designs and met other criteria for evaluating mediation, were collected via literature searches, personal searches of files, and personal communications. Only studies examining the direct effect of the intervention on the hypothesized mediator were considered relevant for this study.

RESULTS

Based on our criteria, the adult literature search yielded ten studies and the child literature search yielded two studies. The most common mediators examined included behavioral processes of change, cognitive processes of change, self-efficacy, decisional balance, social support, and enjoyment. Research indicates that behavioral processes are likely mediators. There was some support for the importance of self-efficacy as a mediator.

CONCLUSIONS

Few studies have used statistically recommended methods to examine mediators in PA intervention studies. Therefore, definitive conclusions about the importance of the mediators reviewed are not possible at this time. Additional PA mediator-intervention studies using recommended statistical methods are necessary to truly test if theory-based PA interventions are effective due to predicted changes in theoretical constructs.

Environmental Influences and What Have We Learned From Dietary Behavior Change With Children?

Sparse research exists on factors influencing use of dietary supplements or on programs to increase dietary supplement use among children. Borrowing from the literature concerning influences on children's diet, parents likely influence children's dietary supplement intake by controlling their availability and accessibility at home and through parenting and socialization strategies. Borrowing from the literature on programs to change diet, programs to promote dietary supplements will likely work when implemented with highly motivated individuals, delivered by specialists and promoting increased, rather than decreased, consumption. Research into these areas is warranted.

Relative contribution of psychosocial variables to the explanation of physical activity in three population-based adult samples

BACKGROUND

Despite large differences in physical activity by demographic subgroup, few studies have identified correlates for specific age and sex groups. The present study quantified the unique variance accounted for in each subgroup by the main psychosocial variables.

METHODS

Three random samples, ages 16-25, 35-45, and 50-65, with a total of 2,390 Belgian subjects, completed psychosocial questionnaires and were interviewed at home.

RESULTS

Social influences, self-efficacy, perceived benefits, and perceived barriers varied in importance by age and sex groups. Social variables provided the most unique information about physical activity for all age and sex groups, except older females. Competition was a significant perceived benefit only for young men, whereas health was the most significant perceived benefit for young women. Among older women and men, health concerns were significant perceived barriers to participation in physical activity.

CONCLUSIONS

The present results provide hypotheses about mediators of physical activity that can be applied in interventions tailored to the needs of various subgroups.

Factorial invariance and latent mean structure of questionnaires measuring social-cognitive determinants of physical activity among black and white adolescent girls

BACKGROUND

We previously developed questionnaires based on contemporary theories to measure physical activity determinants among youth [Motl et al., Prev Med 2000; 31:584-94]. The present study examined the factorial invariance and latent mean structure of unidimensional models fit to the questionnaires measuring attitude, subjective norm, perceived behavioral control, and self-efficacy about physical activity among black and white adolescent girls.

METHODS

Black (n = 896) and white (n = 823) girls in the 8th grade completed the questionnaires measuring attitude, subjective norm, perceived behavioral control, and self-efficacy about physical activity. The responses were subjected to analyses of factorial invariance and latent mean structure using confirmatory factor analysis with full-information maximum likelihood estimation in AMOS 4.0.

RESULTS

The unidimensional models of the four questionnaires generally demonstrated invariance of the factor structure, factor loadings, and factor variance across race but not invariance of the variance-covariance matrices or item uniquenesses. The analyses of latent mean structure demonstrated that white girls had higher latent mean scores on the measures of attitude and self-efficacy than black girls; there were similar, but smaller, differences between white and black girls on the measures of subjective norm and perceived behavioral control.

CONCLUSIONS

The questionnaires can be employed in interventions to test the mediating influences of attitude, subjective norm, perceived behavioral control, and self-efficacy on participation in physical activity by black and white adolescent girls.

Exercise and the transtheoretical model: a longitudinal test of a population sample

BACKGROUND

The purpose of this study was to test the ability of the Transtheoretical Model (TTM) to predict exercise stage transition of individuals in a large, untreated-population-based, random sample of Canadian adults (18-65 years of age) over two consecutive time periods.

METHODS

Assessments of TTM's stage of exercise behavior change, self-efficacy, pros, cons, experiential processes, and behavioral processes were made at baseline (time 1), 6 months (time 2), and 1 year (time 3). Six hundred eighty-three men and women, identified through random-digit telephone dialing, completed all measures across the three time points. Within each time period (time 1-2; time 2-3) participants were categorized as having regressed (moved back at least on stage), remained (no stage change), or progressed (moved forward at least one stage). Baseline TTM constructs were analyzed for their ability to predict change transition across the two time periods.

RESULTS

Of 40 possible predictions (20 for each time period) 18 (45%) were supported.

CONCLUSIONS

Overall, the findings demonstrate partial support for the internal validation of TTM in the exercise domain. Implications of the findings are discussed and future directions for researchers, practitioners, and program planners are provided.

Measuring enjoyment of physical activity in adolescent girls

BACKGROUND

Enjoyment has been implicated as a determinant of physical activity among youth, but advances in understanding its importance have been limited by the use of measures that were not adequately validated. The present study examined: (1) the factorial validity of the Physical Activity Enjoyment Scale (PACES), and (2) the construct validity of PACES scores.

METHODS

Adolescent girls (N=1797), who were randomly assigned to calibration (n=899) and cross-validation (n=898) samples, completed the PACES and measures of factors influencing enjoyment of physical education, physical activity, and sport involvement. The factorial validity of the PACES and the measure of factors influencing enjoyment of physical education was tested using exploratory and confirmatory factor analysis. The hypothesized relationships among the measures were tested using structural equation modeling.

RESULTS

Unidimensional models fit the PACES and the measure of factors influencing enjoyment of physical education in the calibration and cross-validation samples. The hypothesized relationships between the PACES and the measures of factors influencing enjoyment of physical education, physical activity, and sport involvement were supported in the entire sample, were similar in African-American and Caucasian girls, and were independent of physical fitness.

CONCLUSIONS

Evidence of factorial validity and convergent evidence for construct validity indicate that the PACES is a valid measure of physical activity enjoyment among adolescent girls, suitable for use as a mediator variable in interventions designed to increase physical activity.

Physical activity outcomes of CHAMPS II: a physical activity promotion program for older adults

BACKGROUND

Despite well-known benefits of physical activity for older adults, about two thirds are underactive. Community-based programs are needed to facilitate increased physical activity. We examine the effectiveness of CHAMPS II, an inclusive, choice-based physical activity promotion program to increase lifetime physical activity levels of seniors. CHAMPS guided participants to choose activities that took into account their health, preferences, and abilities. It offered information on ways for them to exercise safely, motivate themselves, overcome barriers, and develop a balanced exercise regimen.

METHODS

A 1-year randomized controlled trial was conducted with physically underactive seniors in a multispecialty group practice. Changes in self-reported physical activity by group were evaluated using ANCOVA, controlling for age and sex.

RESULTS

Of 173 randomized subjects, 164 (95%) completed the trial. Subjects were aged 65 to 90 years (M = 74, SD = 6); 66% were female. The intervention group increased estimated caloric expenditure by 487 calories/week in moderate (or greater) intensity activities (MET >/= 3.0; p <.001) and by 687 calories/week in physical activities of any intensity (p <.001). Control group changes were negligible. Between-group analyses found that the changes were significantly different in both measures (p values <.05). Overweight persons especially benefited from this program. The program was as effective for women, older adults (75+), and those who did not set aside time to exercise at baseline.

CONCLUSIONS

The program led to meaningful physical activity increases. Individually tailored programs to encourage lifestyle changes in seniors may be effective and applicable to health care and community settings.

Physician-based activity counseling: intervention effects on mediators of motivational readiness for physical activity

In theory-based interventions for behavior change, there is a need to examine the effects of interventions on the underlying theoretical constructs and the mediating role of such constructs. These two questions are addressed in the Physically Active for Life study, a randomized trial of physician-based exercise counseling for older adults. Three hundred fifty-five patients participated (intervention n = 181, control n = 174; mean age = 65.6 years). The underlying theories used were the Transtheoretical Model, Social Cognitive Theory and the constructs of decisional balance (benefits and barriers), self-efficacy, and behavioral and cognitive processes of change. Motivational readiness for physical activity and related constructs were assessed at baseline, 6 weeks, and 8 months. Linear or logistic mixed effects models were used to examine intervention effects on the constructs, and logistic mixed effects models were used for mediator analyses. At 6 weeks, the intervention had significant effects on decisional balance, self-efficacy, and behavioral processes, but these effects were not maintained at 8 months. At 6 weeks, only decisional balance and behavioral processes were identified as mediators of motivational readiness outcomes. Results suggest that interventions of greater intensity and duration may be needed for sustained changes in mediators and motivational readiness for physical activity among older adults.

Physical activity and determinants of physical activity in obese and non-obese children

OBJECTIVE

To compare the physical activity (PA) patterns and the hypothesized psychosocial and environmental determinants of PA in an ethnically diverse sample of obese and non-obese middle school children.

DESIGN

Cross-sectional study.

SUBJECTS

One-hundred and thirty-three non-obese and 54 obese sixth grade children (mean age of 11.4+/-0.6). Obesity status determined using the age-, race- and gender-specific 95th percentile for BMI from NHANES-1.

MEASUREMENTS

Objective measurements were collected of PA over a 7-day period using the CSA 7164 accelerometer: total daily counts; daily moderate (3-5.9 METs) physical activity (MPA); daily vigorous physical activity (> or =6 METs; VPA); and weekly number of 5, 10 and 20 min bouts of moderate-to-vigorous physical activity (> or =3 METs, MVPA). Self-report measures were collected of PA self-efficacy; social influences regarding PA, beliefs about PA outcomes; perceived PA levels of parents and peers, access to sporting and/or fitness equipment at home, involvement in community-based PA organizations; participation in community sports teams; and hours spent watching television or playing video games.

RESULTS

Compared to their non-obese counterparts, obese children exhibited significantly lower daily accumulations of total counts, MPA and VPA as well as significantly fewer 5, 10 and 20 min bouts of MVPA. Obese children reported significantly lower levels of PA self-efficacy, were involved in significantly fewer community organizations promoting PA and were significantly less likely to report their father or male guardian as physically active.

CONCLUSIONS

The results are consistent with the hypothesis that physical inactivity is an important contributing factor in the maintenance of childhood obesity. Interventions to promote PA in obese children should endeavor to boost self-efficacy perceptions regarding exercise, increase awareness of, and access to, community PA outlets, and increase parental modeling of PA.

Mediating mechanisms in a program to reduce intentions to use anabolic steroids and improve exercise self-efficacy and dietary behavior

This study investigated the mediating mechanisms responsible for the effects of a program designed to reduce intentions to use anabolic steroids, improve nutrition, and increase strength training self-efficacy. Fifteen of 31 high school football teams (N = 1,506 players at baseline) in Oregon and Washington were assigned to receive the intervention. The multicomponent program addressed the social influences promoting ergogenic drug use and engaging students in healthy nutrition and strength training alternative behaviors. Although the results differed across the three dependent variables, the program appeared to work by changing team norms. Unlike prevention of other drugs, changes in knowledge and perceived severity were mediators of program effects in this study.

The behavioral determinants of exercise: implications for physical activity interventions

In light of the well-documented health benefits of physical activity and the fact that the majority of adult men and women are inactive, promoting regular physical activity is a public health priority. This chapter reviews current research findings regarding the determinants of exercise behavior. It also discusses the implications of this knowledge for individual and public health recommendations and intervention strategies for promoting physical activity. The discussion is predicated on the belief that physical activity is a complex, dynamic process. During their lives, individuals typically move through various phases of exercise participation that are determined by diverse factors. This chapter discusses physical activity determinants in two broad categories: individual characteristics, including motivations, self-efficacy, exercise history, skills, and other health behaviors; and environmental characteristics such as access, cost, and time barriers and social and cultural supports.

The importance of the social environment for physically active lifestyle--results from an international study

Physically active lifestyles are regularly associated with improved health and quality of life. Differences in lifestyles in society can partly be understood through the differences in the social and physical environment. This study examines the relationships between reported physical activity, and the extent of perceived support for physical activity in the physical and policy environment (e.g. facilities, programmes and other opportunities), and in the social environment. The data for the study come from a cross-cultural health policy study called MAREPS. In total, 3342 adults, 18 years or older, from six countries (Belgium, Finland, Germany, The Netherlands, Spain, Switzerland) were interviewed via telephone. Respondents were categorised as active or inactive according to self-reported physical activity. Social environmental factors and physical and policy environmental factors were also assessed. The analysis of the data was informed by social cognitive theory, although the study was not originally designed for this purpose. Sixty-eight percent of females and 70% of males were active. The proportions of active and inactive varied by countries to a great extent. The strongest independent predictor of being physically active was social environment. Those who perceived low social support from their personal environment (i.e. family, friends, school and workplace) were more than twice as likely to be sedentary compared to those who reported high social support from their personal environment. Specific knowledge of the programmes and actions for physical activity and sport was also a strong predictor of being active. A supportive physical and policy environment was not associated with participation in physical activity as strongly as had been anticipated. The variation between countries was stronger predictor of being active than the physical and policy environment variables. This study generates the hypotheses and raises the questions that in a preliminary way, there appears to be some relationships between aspects of physical and social environment and physical activity participation. However, future research is needed to refine and clarify this.

Factorial validity and invariance of questionnaires measuring social-cognitive determinants of physical activity among adolescent girls

BACKGROUND

There are few theoretically derived questionnaires of physical activity determinants among youth, and the existing questionnaires have not been subjected to tests of factorial validity and invariance. The present study employed confirmatory factor analysis (CFA) to test the factorial validity and invariance of questionnaires designed to be unidimensional measures of attitudes, subjective norms, perceived behavioral control, and self-efficacy about physical activity.

METHODS

Adolescent girls in eighth grade from two cohorts (N = 955 and 1,797) completed the questionnaires at baseline; participants from cohort 1 (N = 845) also completed the questionnaires in ninth grade (i.e., 1-year follow-up). Factorial validity and invariance were tested using CFA with full-information maximum likelihood estimation in AMOS 4.0. Initially, baseline data from cohort 1 were employed to test the fit and, when necessary, to modify the unidimensional models. The models were cross-validated using a multigroup analysis of factorial invariance on baseline data from cohorts 1 and 2. The models then were subjected to a longitudinal analysis of factorial invariance using baseline and follow-up data from cohort 1.

RESULTS

The CFAs supported the fit of unidimensional models to the four questionnaires, and the models were cross-validated, as indicated by evidence of multigroup factorial invariance. The models also possessed evidence of longitudinal factorial invariance.

CONCLUSIONS

Evidence was provided for the factorial validity and the invariance of the questionnaires designed to be unidimensional measures of attitudes, subjective norms, perceived behavioral control, and self-efficacy about physical activity among adolescent girls.

Studying adherence to therapeutic regimens: overview, theories, recommendations

Prediction of adherence and planning of behavior change can be systematically accomplished by using or modifying well-investigated theories. An overview of these models and recommendations for their use is offered. Control Clin Trials 2000;21:156S-163S

Self rating of health is associated with stressful life events, social support and residency in East and West Berlin shortly after the fall of the wall

STUDY OBJECTIVE

To compare the health status and factors influencing the health of populations that had previously lived under different political systems.

DESIGN

Cross sectional health and social survey using postal interviews. The relation between self reported health and psychosocial factors (stressful life events, social support, education, health promoting life style and health endangering behaviour) was investigated. To determine East-West differences a logistic regression model including interaction terms was fitted.

SETTING

East and West Berlin shortly after reunification 1991.

PARTICIPANTS

Representative sample of 4430 Berlin residents aged 18 years and over (response rate 63%).

RESULTS

Of all respondents, 15.4% rated their health as unsatisfactory. Residents of East Berlin rated their health more frequently as unsatisfactory than residents of West Berlin (Or(age adjusted)= 1.29, 95%CI 1.08, 1.52), these differences occurred predominantly in the over 60 years age group. Logistic regression showed significant independent effects of stressful life events, social support, education, and health promoting life style on self rated health. The effects of education and health promoting life style were observed to be more pronounced in the western part of Berlin. Old age and female sex showed a stronger association with unsatisfactory health status in the eastern part of Berlin.

CONCLUSIONS

For subjects aged over 60 years there was evidence that living in the former East Berlin had an adverse effect on health compared with West Berlin. The impact of education and a health promoting lifestyle on self rated health seemed to be weaker in a former socialist society compared with that of a Western democracy. This study supports an "additive model" rather than a "buffering model" in explaining the effects of psychosocial factors on health.

Effects of leadership style and group dynamics on enjoyment of physical activity

PURPOSE

The primary purpose of this study was to examine the independent and combined effects of leadership style and group dynamics on the enjoyment of physical activity.

DESIGN

A completely randomized 2 x 2 factorial design was used in which the manipulation of "leadership style" (socially enriched vs. bland) was crossed with a manipulation of "group dynamics" (socially enriched vs. bland).

SETTING

The study was conducted in an aerobics studio on a university campus.

SUBJECTS

The sample included 48 male and 42 female undergraduate students who were moderately active.

INTERVENTION

Each participant was involved in a single session of step aerobics. A female graduate student provided either an enriched or bland series of interactions to manipulate leadership style, and a trained group of planted undergraduates was used to promote either an enriched or bland group environment.

MEASURES

The outcome measures of interest were enjoyment and the probability of engaging in a similar activity in the future.

RESULTS

Participants in the enriched leadership style plus enriched group dynamics condition reported higher enjoyment than did participants in the other three conditions. On average, the level of enjoyment was 22.07% higher in this condition than in the other three conditions (p < .001). The probability of future involvement was 13.93% higher for participants in the enriched group environment, irrespective of leadership style (p < .03).

CONCLUSIONS

Enjoyment during physical activity is optimized when a positive and supportive leadership style is coupled with an enriched and supportive group environment. Future research is required to extend these findings to other activities and populations.

Impact of a worksite behavioral skills intervention

Sixty-four male and female sedentary employees were randomly assigned to an intervention group or control group to determine the effects of behavioral skill training on adoption and maintenance of exercise. Both received a 9-month membership at a local fitness facility. The control group received a 12-week semistructured course, which included a facility orientation and three meetings with a personal trainer. The intervention group received a 12-week behavioral skills course and were encouraged to participate in a 12-week semistructured exercise course followed by a 3-month problem-solving support intervention. Both groups improved their daily energy expenditure, the amount of moderate and vigorous activity they performed, and their strength and flexibility. The study sample was too small to show substantial differences between the intervention and control group. Changes in mediator variables were mixed.

Project GRAD: two-year outcomes of a randomized controlled physical activity intervention among young adults. Graduate Ready for Activity Daily

INTRODUCTION

Project Graduate Ready for Activity Daily evaluated a program to promote physical activity through the transition of university graduation in a randomized controlled trial.

METHODS

Three hundred thirty-eight university seniors participated in either a cognitive-behavioral intervention course or a knowledge-oriented general health course during the semester before graduation. Behaviorally oriented phone and mail follow-up was delivered to the intervention group for 18 months. Physical activity outcomes and mediating variables were assessed at baseline, 1 and 2 years (93% retention rate).

RESULTS

There were no significant intervention effects on physical activity outcomes at 2 years for either men or women. Experiential and behavioral processes of change were significantly improved for intervention women over 2 years.

CONCLUSIONS

Despite excellent participation in a theoretically based, well-attended intervention, few long-term effects on physical activity or its mediators were found. Additional research is needed to determine optimal interventions for physical activity and to validate or alter current behavior change theory.