Journal of Gerontology: PSYCHOLOGICAL SCIENCES 2006, Vol. 61B, No. 5, P270–P277 Copyright 2006 by The Gerontological Society of America Physical Activity and Functional Limitations in Older Women: Influence of Self-Efficacy Edward McAuley, James F. Konopack, Katherine S. Morris, Robert W. Motl, Liang Hu, Shawna E. Doerksen, and Karl Rosengren Department of Kinesiology, University of Illinois at Urbana-Champaign. This study examined the role of self-efficacy and physical function performance in the relationship between physical activity and functional limitations. Older women (age, M = 68.2 years) completed measures of physical activity, self-efficacy, physical function performance, and functional limitations at the baseline of an ongoing study. Analyses indicated that physical activity was associated with self-efficacy for exercise, efficacy for gait and balance, and physical function performance. Both measures of efficacy and physical functional performance were associated with functional limitations. Demographic and health status variables did not differentially influence these relationships. Although cross-sectional in nature, our findings suggest that physical activity, self-efficacy, and functional performance may all play a role in reducing functional limitations. Of particular relevance is the fact that both physical activity and self-efficacy represent important, modifiable factors that can enhance function. I T is well established that functional limitations in older adults are important risk factors for subsequent disability and institutionalization (Fried & Guralnik, 1997). Functional limitations are typically manifest as self-reported frequency in restrictions or difficulty in walking, lifting, or carrying, and rates of limitation in function appear to be exacerbated by sedentary behavior (Rejeski, Brawley, & Haskell, 2003). In a recent review of the role played by physical activity in the disablement process, Keysor (2003) concluded that physical activity can have a protective effect on functional limitations in the disablement process. For example, engaging in even a relatively small amount of activity (e.g., walking 1 mile in a week) has been shown to result in a significant slowing of the functional limitation trajectory over a 6-year period (Miller, Rejeski, Reboussin, Ten Have, & Ettinger, 2000). Keysor and Jette (2001) report that there is evidence, if somewhat inconsistent, that being involved in physical activity programs also results in improvements in important physical function performance behaviors, such as walking speed, rising and transferring from a chair, and climbing stairs. Thus, physical function performance involves a quantitative assessment of the behavioral act (e.g., walking speed), whereas functional limitations are perceived restrictions in the frequency of being able to carry out these activities. In past research, it has been common to use either physical function performance measures or self-reported restrictions of activities as indicators of functional limitations. Stewart (2003), however, has argued that such an approach to measurement and definition is too broad to understand potentially subtle influences of physical activity on functional limitations. For example, Jylha, Guralnik, Balfour, and Fried (2001) noted that self-reported restrictions in walking (functional limitations) and objectively measured maximal walking speed (physical function performance) were independently associated with health status in a sample of older women. Stewart suggested that it is necessary for researchers to consider these related, but independent, constructs separately in the disablement process (Verbrugge & Jette, 1994). She has proposed that physical P270 function performance precedes functional limitations in this process. Thus, physical activity would influence functional limitations indirectly through physical function performance. In her review of physical activity and the disablement process, Keysor (2003) noted that one of the key challenges in this area is to identify the underlying mechanisms implicated in this relationship. Although physical function performance is likely to play a role, other psychosocial factors have also been identified as potential mediators. One such factor is selfefficacy, an important social cognitive variable that has been shown to influence a wide array of health behaviors (Bandura, 1997; McAuley & Blissmer, 2000). Self-efficacy expectations are concerned with beliefs in capabilities to successfully carry out courses of action (Bandura). Considerable evidence exists to suggest that efficacy expectations are associated with physical function performance (McAuley & Blissmer). For example, self-efficacy mediated the influence of an exercise intervention on stair climbing in older adults with osteoarthritis of the knee (Rejeski, Ettinger, Martin, & Morgan, 1998). Li and colleagues (2001) provided further evidence for the self-efficacy and physical function performance relationship in a randomized controlled exercise trial. Moreover, Seeman and colleagues (Seeman & Chen, 2002; Seeman, Unger, McAvay, & Mendes de Leon, 1999) reported that self-efficacy expectations were related to disability and functional declines and that selfefficacy influenced disability independent of physical abilities. Aspects of self-efficacy likely to be implicated in these relationships might encompass beliefs relative to exercise and gait and balance capabilities. In addition, the physical activity and self-efficacy relationship has been well documented in the literature, whereby selfefficacy is both a determinant and an outcome of physical activity (McAuley & Blissmer, 2000). Therefore, it would appear that one possible way to understand the relationship between physical activity and functional limitations may be through the pathways of self-efficacy and physical function performance. That is, more active individuals could be argued to be more efficacious, which would lead to better physical SELF-EFFICACY AND PHYSICAL FUNCTION P271 Figure 1. Alternative models of the hypothesized relationships among physical activity, self-efficacy, physical function performance, and functional limitations: (a) self-efficacy influences functional limitations through functional performance; (b) self-efficacy has independent associations with functional limitations and also operates through physical function performance. function. Being able to function better would then be associated with fewer functional restrictions or limitations. The proposed relations are shown in Figure 1(a), where efficacy relative to both balance and gait tasks and exercise are represented. An alternative model, shown in Figure 1(b) and based on the arguments of Keysor (2003) and Rejeski and colleagues (1998), would suggest that self-efficacy also has independent associations with functional limitations in addition to operating through physical function performance. In the present study, we tested the proposed relationships in the context of baseline data from a sample of older women at entry into an ongoing prospective study. METHODS Participants and Recruitment Older (age, M ¼ 68.12 years; range ¼ 59–84 years) Black (n ¼ 81) and White (n ¼ 168) women were recruited to participate in a 24-month prospective study of women’s health status. Inclusion criteria were sufficiently flexible as to permit recruitment of a sample of older women closely representative of the general population. Recruitment sources included local media advertising, area health facilities, churches, and senior centers. A total of 298 individuals were initially contacted following recruitment, with 49 being excluded as ineligible or declining participation. Further details with respect to inclusion criteria and recruitment methods have been reported elsewhere (McAuley, Konopack, Motl, Rosengren, & Morris, 2005). Measures Demographic and health information. —Each participant provided current demographic information and details of her health history. As participants’ health status may have implications for physical function performance and functional limitations, we constructed a health status measure from the health history questions. Specifically, participants indicated whether or not they suffered from any of the following health conditions: cardiovascular disease, pulmonary disease, functional impairment of the skeletomuscular system, hypertension, and diabetes. We summed these responses to provide a health status index that ranged from 0 to 5. Approximately 70% (n ¼ 173) of the study participants reported having one or more of these health conditions. Further information with respect to P272 McAULEY ET AL. baseline health status information has been reported elsewhere (McAuley et al., 2005). Functional limitations. —We used the abbreviated version (McAuley et al., 2005) of the function component of the LateLife Function and Disability Instrument (LL-FDI; Haley et al., 2002; Jette et al., 2002) to assess reported difficulty in executing discrete activities. This measure is composed of three five-item subscales assessing advanced lower extremity function, basic lower extremity function, and upper extremity function. Individuals are asked to rate the extent to which they feel limited in performing certain activities by selecting a value from 1 (cannot do) to 5 (none). We calculated a total score for each subscale by summing ratings of all five items, resulting in a possible range of 5–25, with higher scores reflecting less difficulty in performing tasks. In the present analyses only the measures of lower extremity function were used, as efficacy scales pertained to lower body mobility and physical function performance tasks were exclusive to the lower extremities. Physical activity participation. —We assessed physical activity with two measures, the Physical Activity Scale for the Elderly (PASE; Washburn, Smith, Jette, & Janney, 1993) and the Community Healthy Activities Model Program for Seniors (CHAMPS; Stewart et al., 2001). The PASE is a paper-and-pencil questionnaire whereas the CHAMPS is an interviewer-administered measure of physical activity. Both measures have been widely used to assess physical activity in older adults. Physical function performance. —Gait speed was assessed by using normal walking speed over a 7-m pathway and timed ascent and descent of a flight of 15 stairs. The final performance measure was the timed 8-Foot Up-and-Go (Rikli & Jones, 1999), which assessed participants’ ability to rise from a seated position, walk a distance of 8 ft (2.43 m) as quickly as possible, and return to a seated position. Thus, all lower scores (faster times) in all physical function performance measures represent better performance. Self-efficacy. —We assessed self-efficacy by using measures of beliefs in capabilities relative to maintaining one’s balance, ambulating over objects, walking, and general exercise. We used the Activity-Specific Balance Confidence Scale (ABC; Powell & Myers, 1995) to assess individuals’ confidence in their ability to perform various basic activities of daily living without compromising their balance. The six-item Gait Efficacy Scale (GES; McAuley, Mihalko, & Rosengren, 1997) was used to assess individuals’ beliefs in their capability to negotiate stairs and objects in their path. We also used the Exercise Self-Efficacy Scale (EXSE; McAuley, 1993), which measured individuals’ beliefs in their ability to accumulate 30 min or more of physical activity per day on 5 or more days per week in the future. Finally, we used the Self-Efficacy for Walking Scale (SEW; McAuley, Courneya, & Lettunich, 1991) to assess beliefs in capabilities to successfully walk for a specified duration of time, ranging from 5- to 40-min bouts, at a moderately fast pace without stopping. For each measure, we calculated an efficacy score by summing all given response scores and dividing by the total number of items, resulting in a possible range of 0–100. In subsequent analyses, these variables were used to represent a latent exercise efficacy factor (SEW and EXSE) and a latent gait and balance efficacy factor (GES and ABC). All efficacy measures had excellent internal consistencies in the current study (a . 0.90). Procedures Participants completed all measures at the baseline of an ongoing 24-month prospective study of physical activity and health status in older women. Upon entry into the study and completion of approved Institutional Review Board informed consent, participants completed questionnaires assessing basic demographic information, physical activity (PASE), selfefficacy, and general health information. Interviewers collected the LL-FDI and CHAMPS data. Two trained testers assessed physical function performance measures in a laboratory. They assessed time taken to walk down and up a flight of 15 stairs as participants entered and left the laboratory, respectively. They assessed participants’ height and weight upon their entry into the laboratory; participants then completed the walking task at their normal walking pace and the 8-Foot Up-and-Go as quickly as possible. For all timed tasks, two experimenters used handheld stopwatches to time the participants. Each condition (with the exception of the stairs ascent and descent) was repeated twice, and the best times were used in subsequent analyses. Data Analysis We analyzed the data using covariance modeling with the full-information maximum likelihood (FIML) estimator in Mplus 3.11 (Muthén & Muthén, 1998–2004). FIML is an optimal method for the treatment of missing data in structural equation modeling that has yielded accurate parameter estimates and fit indices with simulated missing data (Arbuckle, 1996; Enders, 2001; Enders & Bandalos, 2001). Missing data composed 3.2% of the PASE data (n ¼ 8), 1.2% of the Stairs– up data (n ¼ 3), and 0.5% of Stairs–down data (n ¼ 1). Reasons for missing data included failure or refusal to return the PASE questionnaire and inability to walk up or down stairs as the result of a disability. There were no missing data for any of the other variables. Model testing. —As we had multiple indicators of each construct, we used a latent variable framework to examine the proposed relationships among constructs. We analyzed the data by using a two-step procedure (Anderson & Gerbing, 1988). The first step involved a confirmatory factor analysis that tested the fit of an overall measurement model. The overall measurement model is presented in Figure 2 and consisted of five correlated latent variables. These latent constructs comprised physical activity (CHAMPS and PASE), exercise self-efficacy (EXSE and SEW), gait and balance self-efficacy (ABC and GES), physical function performance (Stairs–up and Stairs– down, 8-Foot Up-and-Go, 7-m walking speed), and functional limitations (LL-FDI lower body function scales). Because of the similarity of assessment methods for the stair-climbing tasks, we allowed a correlated uniqueness between the Stairs– up and Stairs–down indicators of the functional performance latent variable. SELF-EFFICACY AND PHYSICAL FUNCTION P273 Figure 2. Overall measurement model illustrating the relationships among the five latent variables tested by use of confirmatory factor analysis (PASE ¼ Physical Activity Scale for the Elderly; CHAMPS ¼ Community Healthy Activities Model Program for Seniors; EXSE ¼ Exercise SelfEfficacy Scale; SEW ¼ Self-Efficacy for Walking Scale; ABC ¼ Activity-Specific Balance Confidence Scale; GES ¼ Gait Efficacy Scale; ALEF ¼ Function and Disability Instrument’s advanced lower extremity function; BLEF ¼ Function and Disability Instrument’s basic lower extremity function). The second step involved testing the proposed structural models shown in Figure 1 on the basis of the hypothesized relationships among the latent variables. Model 1a specified (a) direct effects of physical activity on exercise self-efficacy and gait and balance self-efficacy; (b) direct effects of physical activity, exercise self-efficacy, and gait and balance selfefficacy on physical function performance; (c) a direct effect of physical function performance on functional limitations; and (d) a single correlation between disturbance terms for the exercise and gait and balance self-efficacy latent variables (not depicted in Figure 1). As the measured constructs of the two latent efficacy factors reflect related aspects of physical activity, there is both conceptual and theoretical sense for allowing this covariation. Next, we compared the fit of this model with the alternative model shown in Figure 1(b). This involved testing the same paths proposed in Model 1a but with additional paths from the two self-efficacy factors to functional limitations. Covariates. —We conducted a final analysis in which we used age, race, and health status as covariates in the best-fitting model to determine whether the fit of the model and the proposed relationships were differentially influenced by these important health and demographic variables. Model fit. —We assessed the fit of the model to the data by using the chi-square statistic, root mean square error of approximation (RMSEA), standardized root mean square residual (SRMR), and the Comparative Fit Index (CFI). The chi-square statistic assessed absolute fit of the model to the data (Jöreskog & Sörbom, 1996). The SRMR is the average standardized residual value derived between the variance–covariance matrix for the hypothesized model and the variance–covariance matrix of the sample data (Bollen, 1989). The value of the SRMR should approximate or be smaller than .08 for a good-fitting model (Hu & Bentler, 1999). The RMSEA represents closeness of fit, and values approximating .06 are indicative of a close fit (Browne & Cudeck, 1993). The CFI tests the proportionate improvement in fit by comparing the hypothesized model with the independence model (Bentler, 1990). The value of the CFI should approximate 0.95 or greater for a good-fitting model (Hu & Bentler, 1999). RESULTS Descriptive Statistic Descriptive statistics and correlations among all measures included in the data analysis are presented in Table 1. Step 1: Confirmatory Factor Analyses The five-factor measurement model depicted in Figure 2 represented a good fit for the data (v2 ¼ 120.71, df ¼ 43, SRMR ¼ 0.04, RMSEA ¼ 0.08, CFI ¼ 0.96). Although the value of the chi-square was statistically significant ( p , .001), the RMSEA, SRMR, and CFI approximate criteria for a good model–data fit. The factor loadings for the indicators on each of the latent variables were all statistically significant ( p , .05), suggesting that the measures were acceptable indicators of the latent variables. The correlations among latent variables are presented in Table 2 and were all statistically significant and moderate to large in magnitude. Recall that a higher score reflects fewer functional limitations and that better physical function performance is represented by lower scores (i.e., faster times). Specifically, women who were more active had higher gait and balance efficacy and exercise self-efficacy, better physical function, and reported fewer functional limitations. Being more efficacious was associated with better physical functioning and fewer functional limitations. Finally, poorer functional performance was associated with greater frequency of functional limitations. McAULEY ET AL. P274 Table 1. Correlations and Descriptive Statistics for All Measures Variable 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1. Age (years) 68.1 (6.1) 2. Health statusa 0.11 1.1 (1.0) 3. FDI: ALEF 0.24** 0.41** 17.9 (4.8) 4. FDI: BLEF 0.14* 0.35** 0.64** 23.6 (2.3) 5. CHAMPSb,c 0.04 0.15* 0.33** 0.19** 20.2 (10.2) 6. PASEb 0.20** 0.28* 0.40** 0.20** 0.36** 156.4 (70.9) 7. 7-m walk (s) 0.27** 0.33** 0.50** 0.38** 0.19** 0.24** 6.7 (1.7) 8. Stair ascent (s) 0.18** 0.32** 0.61** 0.43** 0.27** 0.35** 0.66** 9.8 (3.4) 9. Stair descent (s) 0.26** 0.39** 0.58** 0.51** 0.31** 0.38** 0.63** 0.85** 9.7 (4.0) 10. 8-Foot Up-and-Go (s) 0.35** 0.27** 0.54** 0.52** 0.16* 0.24** 0.71** 0.69** 0.65** 7.0 (1.7) 11. ABC 0.13* 0.39** 0.58** 0.53** 0.22** 0.31** 0.35** 0.46** 0.53** 0.41** 90.9 (13.2) 12. GES 0.10 0.43** 0.67** 0.57** 0.20** 0.31** 0.44** 0.56** 0.54** 0.49** 0.85** 88.2 (18.4) 13. SEWb 0.23** 0.40** 0.65** 0.38** 0.34** 0.34** 0.42** 0.46** 0.45** 0.42** 0.50** 0.53** 71.7 (31.8) b 14. EXSE 0.15* 0.28** 0.49** 0.35** 0.39** 0.36** 0.37** 0.40** 0.40** 0.34** 0.47** 0.48** 0.68** 80.9 (28.1) Notes: *p , .05; **p , .01; FDI ¼ Function and Disability Inventory, ALEF ¼ Advanced Lower Extremity Function, BLEF ¼ Basic Lower Extremity Function, CHAMPS ¼ Community Healthy Activity Model Program for Seniors, PASE ¼ Physical Activity Scale for the Elderly, ABC ¼ Activity-Specific Balance Scale, GES ¼ Gait Efficacy Scale, SEW ¼ Self-Efficacy for Walking Scale, EXSE ¼ Exercise Self-Efficacy Scale. a Health status data reflect prevalence of chronic conditions. b These descriptive data were previously published by McAuley and colleagues (2005). c CHAMPS data reflect frequency of activities of all intensities. Step 2: Structural Models The structural model hypothesized in Figure 1(a) provided a relatively poor fit to the data (v2 ¼ 196.36, df ¼ 46, SRMR ¼ 0.06, RMSEA ¼ 0.11, CFI ¼ 0.92) and fit worse than the baseline measurement model. Subsequently, we tested the structural model hypothesized in Figure 1(b). This model involved estimating two additional paths from exercise selfefficacy and gait and balance efficacy to functional limitations. This model provided a good fit to the data (v2 ¼ 122.47, df ¼ 44, SRMR ¼ 0.04, RMSEA ¼ 0.08, CFI ¼ 0.96). The fit of this model represented a substantial improvement over the model in Figure 1(a), v2diff ¼ 73.89, df ¼ 2, p , .001, and did not differ significantly from the measurement model, v2diff ¼ 1.75, df ¼ 1, p . .10. Therefore, the model in Figure 1(b) supports the hypothesized pattern of the relationships among the latent constructs of physical activity, self-efficacy, physical function performance, and functional limitations. Statistically significant path coefficients are shown in Figure 3. As one can see, physical activity was statistically related to both exercise self-efficacy and gait and balance self-efficacy ( ps , .01). In addition, physical activity was significantly associated with physical function performance ( p , .05), as was gait and balance self-efficacy ( p , .01). Physical function performance, in turn, had a statistically significant direct effect Table 2. Correlations Among the Six Latent Variables in the Initial Confirmatory Factor Analysis Latent Variable 1. 2. 3. 4. 5. Physical activity Exercise self-efficacy Balance self-efficacy Functional limitations Functional performance 1 2 — 0.69 0.44 0.63 0.51 — 0.62 0.75 0.58 3 — 0.76 0.62 4 — 0.75 5 — Note: All correlations are statistically significant ( p , .05). Higher scores on functional limitations represent fewer limitations, and lower scores on functional performance indicates better (faster) performance. on functional limitations ( p , .01), as did exercise self-efficacy and gait and balance self-efficacy ( p , .01). The correlation between exercise and gait and balance self-efficacy was statistically significant ( p , .01). Overall, physical activity and the self-efficacy variables accounted for 47% of the variation in physical function performance, whereas self-efficacy and physical function performance accounted for 78% of the variance in functional limitations. Testing Alternative Models To determine whether adding a direct path from physical activity to functional limitations changed the parameter estimates or added additional variance, we tested an additional model. This path was nonsignificant (b ¼ .13, p . .05), and the pattern of relationships, fit of the model, and variance accounted for remained essentially unchanged (v2diff ¼ 1.76, df ¼ 1, p ..10). One final possible consideration of the relationships among the constructs of interests might be to determine whether the fit of the model changes when one considers the relationships between self-efficacy and functional limitations independent of any influence of physical function performance. Consequently, we retested the model proposed in Figure 3 but did not specify a path from physical function performance to functional limitations. This model proved to be a poorer fit to the data (v2 ¼ 148.30, df ¼ 45, SRMR ¼ 0.05, RMSEA ¼ 0.10, CFI ¼ 0.94) and represented a significantly worse fit than the model in Figure 3 (v2diff ¼ 25.83, df ¼ 1, p , .001). Effects of Covariates on Hypothesized Relationships We next tested the best-fitting model (Figure 3) while statistically controlling for race, age, and health status. Neither the fit of the model, the magnitude of the hypothesized relationships, nor their statistical significance was affected by the inclusion of the covariates in the model. There were, however, some interesting relationships among the covariates and the model components. For example, race exhibited a statistically SELF-EFFICACY AND PHYSICAL FUNCTION P275 significant, although modest, association with physical activity (b ¼ .18, p , .05), functional performance (b ¼.14, p , .05), and functional limitation (b ¼ .14, p , .05). White women reported higher levels of physical activity and performed better on the battery of functional tests than did Black women, but they reported more frequent functional limitations. Older women reported lower levels of physical function performance (b ¼ .23, p , .05). With respect to health status, individuals with more chronic conditions had lower self-efficacy for gait and balance (b ¼.32, p , .05) and exercise (b ¼ .20, p , .05). DISCUSSION In the present study we compared two structural models of the relationship between physical activity and functional limitations in older women at the baseline of an ongoing, 24-month prospective trial. These models were based in part on social cognitive theory (Bandura, 1986) and on Stewart’s (2003) perspective that performance-based measures of function should occupy a distinct step in the disablement process. Initially, we tested the proposition that physical activity had, in part, an indirect effect on physical function performance through self-efficacy as well as a direct effect on physical function performance, which was, in turn, associated with functional limitations. In addition, as self-efficacy has been reported to have an influence on functional limitations that is independent of functional abilities (Seeman et al., 1999), we tested an alternative model that also included direct associations between self-efficacy and functional limitations. Our analyses found this latter model to fit the data best. We believe these findings to be important from several perspectives. First, although physical activity participation has frequently been cited as having a protective effect on functional limitations in older adults (Keysor, 2003; Miller et al., 2000), it would appear that this relationship may operate through physical activity’s association with physical function performance and self-efficacy. Our findings support those of Rejeski and colleagues (1998) in this respect but with one important difference. That is, the association between efficacy and functional limitations in this study was both direct and indirect through functional performance, findings that support work by Seeman and colleagues (Seeman & Chen, 2002; Seeman et al., 1999). Thus, older adults who are more physically active and have stronger beliefs relative to their general physical capabilities appear to display better physical function performance and, in turn, fewer restrictions in daily tasks involving the lower body. Thus, there is support for the position of Keysor and Rejeski and colleagues that self-efficacy is implicated in the relationship between physical activity and functional limitations. Moreover, such findings are in line with reported effects of self-efficacy on other health behaviors (Bandura, 1997). It is important to note that all of the relationships discussed herein were not affected by the inclusion of age, race, and health status as covariates. However, these covariates were associated with variables in the model. For example, as one would expect, older women had poorer physical function performance. Women with more chronic health conditions were less efficacious relative to their gait and balance and capability to be physically active. Finally, White women were more active and had better Figure 3. Best-fitting structural model, with age, health status, and race controlled for. (Note that having better physical function performance is indicated by lower scores and having fewer functional limitations is indicated by higher scores. Unless otherwise indicated, all standardized path coefficients are statistically significant, with p , .05. To improve the clarity of the figure, we did not include the items and uniquenesses; D1–D4 are disturbances, i.e., residual terms.) functional performance but reported more functional limitations. Age and health status are clearly important correlates of efficacy, physical function, and limitations (Bandura, 1997); however, it is equally important that the theoretical relationships proposed in our model did not change in magnitude or significance when these covariates were controlled. Such finding support the work of Seeman and Chen (2002), who reported that functional declines in older adults with chronic disease conditions cannot be solely attributed to health status, as their data suggest that patterns of functional decline may also be inversely related to physical activity participation. Subsequent tests of the proposed associations should continue to consider the roles played by race, age, and health status in the relationship between physical activity and functional limitations. We believe the present study to have a number of strengths. For example, we adopted a social cognitive perspective (Bandura, 1986, 1997) to better understand the relationships among physical activity, functional performance, and functional limitations in a relatively large sample of older women. Furthermore, we assessed each of the constructs of interest by using multiple indicators of each construct rather than relying on single measures. One advantage of using multiple indicators is that these observed variables can be modeled to assess underlying latent constructs. Moreover, such an approach P276 McAULEY ET AL. allows for a more powerful and accurate test of structural relations among theoretically related constructs. This increase in power and accuracy is largely attributable to estimating structural relationships by using latent variables that allow for the partitioning of true, common, and error score variance. Thus, we believe that our current results demonstrate some initial support for the roles played by self-efficacy and functional performance in the physical activity and functional limitations relationship. However, it is important to acknowledge that the models tested are cross-sectional and restricted to a sample of older women. Thus, causal direction cannot be determined, and whether the findings hold in men awaits empirical examination. It could be argued that having functional limitations makes one less active and that relationships in our model could be operating in the reverse direction. Of course, testing such a model would not change the relationships. A social cognitive perspective would argue for reciprocally determining relationships among model constructs, and such relationships can be tested with longitudinal data. Our model testing was driven by both theoretical predictions and empirical research (e.g., Rejeski et al., 1998). Indeed, the fit of the structural model did not differ significantly from that of the measurement model, suggesting that the hypothesized model is one possible explanation for the bivariate relationships among the latent constructs. Thus, tests of models other than those presented are unlikely to demonstrate a more parsimonious fit. Certainly, this does not preclude the possibility of testing alternative models of change among construct relationships over time. Furthermore, it may be that participating in a study of women’s health may have resulted in a self-selected sample biased toward being more active and healthier than the normal population. However, as we noted earlier, approximately 70% of our sample had one or more chronic health conditions, and our sampling frame was relatively flexible to allow for a broad representation of women. Thus, we believe that our findings lay the foundation for subsequent testing of the roles played by self-efficacy and physical function performance in mediating effects of physical activity behavior on functional limitations and, ultimately, disability in older women. In conclusion, our results support a growing body of research showing that lifestyle factors such as physical activity and psychosocial factors such as self-efficacy appear to be implicated in functional limitations in older adults (Keysor, 2003; Rejeski et al., 1998; Seeman & Chen, 2002; Seeman et al., 1999). 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