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CAUSAL ANALYSIS OFEXERCISE AND CALCIUMINTAKE BEHAVIORSFOR OSTEOPOROSISPREVENTION AMONGYOUNG WOMEN INTHAILANDNoppawan Piaseu a , Karen Schepp b &Basia Belza ca School of Nursing, University ofWashington, Seattle, Washington, USAb Department of Psychosocial andCommunity Health, School of Nursing,University of Washington, Seattle,Washington, USAc Department of Biobehavioral Nursingand Health Systems, School of Nursing,University of Washington, Seattle,Washington, USAPublished online: 10 Nov 2010.

To cite this article: Noppawan Piaseu , Karen Schepp & Basia Belza (2002)CAUSAL ANALYSIS OF EXERCISE AND CALCIUM INTAKE BEHAVIORS FOR

OSTEOPOROSIS PREVENTION AMONG YOUNG WOMEN IN THAILAND, HealthCare for Women International, 23:4, 364-376

To link to this article: http://dx.doi.org/10.1080/0739933029008937

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Health Care for Women International , 23:364–376, 2002Copyright © 2002 Taylor & Francis0739-9332 /02 $12.00 + .00DOI: 10.1080/073993302900893 7

CAUSAL ANALYSIS OF EXERCISE ANDCALCIUM INTAKE BEHAVIORS FOR

OSTEOPOROSIS PREVENTION AMONG YOUNGWOMEN IN THAILAND

Noppawan Piaseu, RN, MS, MSNSchool of Nursing, University of Washington, Seattle, Washington, USA

Karen Schepp, RN, PhDDepartment of Psychosocial and Community Health, School of Nursing,

University of Washington, Seattle, Washington, USA

Basia Belza, RN, PhDDepartment of Biobehavioral Nursing and Health Systems, School of Nursing,

University of Washington, Seattle, Washington, USA

The goal of health education is to provide information to affect attitudes, beliefs, andintentions for behavior change. However, little is known about the effects of changesin knowledge on behaviors for osteoporosis prevention.

Our objective is to develop and test theoretical models of the effects of knowledge,attitude, and self-ef� cacy on exercise and calcium intake among young women beforeand after an intervention program. First, we hypothesized that knowledge wouldpositively predict attitude, self-ef� cacy, calcium intake, and exercise. Second, attitudewould positively predict self-ef� cacy, calcium intake, and exercise. Third, self-ef� cacywould positively predict calcium intake and exercise. Fourth, attitude and self-ef� cacywould mediate the effect of knowledge on calcium intake and exercise.

At the beginning and end of the study, participants in the control group andintervention group completed the osteoporosis knowledge test, the osteoporosi s healthbelief scale, the osteoporosis self-ef� cacy scale, a self-report for food records, andexercise.

The causal model was examined as a result of our study. After the interventionprogram, calcium intake and exercise were predicted by knowledge when mediated

Received March 2001; accepted 17 August 2001.I am thankful to the participants for their cooperation; Pamela Mitchell, RN, PhD, CNRN,

FAAN, for her scholarly guidance; the reviewer for helpful comments; Rajata Rajatanavin,MD, for sharing his expertise in osteoporosis and con� rming the translated instruments; andPongamorn Bunnag, MD, for the process of back translation. Financial support was providedto the � rst author by the Thai government and the University of Washington School of Nursing.

Address correspondence to Noppawan Piaseu, School of Nursing, University of Washington,Box 357260, Seattle, WA 98195-7260, USA. E-mail: noppawan@u.washington.edu

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Causal Analysis 365

by attitudes and self-ef� cacy. The � nal model accounted for 30% and 45% of thevariance in calcium intake and exercise, respectively.

We conclude that interventions to enhance young women’s knowledge and self-ef� cacy may result in increased calcium intake and exercise.

Osteoporosis is a chronic condition characterized by a decrease in bone massand an increase in susceptibility to fractures. Age-speci� c hip fractures increaseexponentially in Thai women after the age of 60 (Suriyawongpaisal et al., 1994). Thelongevity of Thai women is increasing and is associated with increasing numbersof women who sustain hip fracture. Consequently, osteoporosis is an increasinghealth problem in Thailand. Overall, it is estimated that the number of annual hipfractures will increase from 1.66 million in 1990 to 6.26 million by 2050, implying anurgent need for preventive strategies (Cooper, Campion, & Melton, 1992). Therefore,prevention is of critical importance.

Researchers suggest that the majority of women of all ages have inadequateinformation about osteoporosis risk factors and preventive behavior (Ailinger &Emerson, 1998; Ribeiro, Blakeley, & Laryea, 2000). Moreover, they do not takeadequate action to prevent osteoporosis (Ribeiro et al., 2000). Accordingly, usingcurrent practices in health education, we tend to provide people with informationintended to affect their attitudes, beliefs, and intentions for behavior change (West& Lieberman, 1985). However, very little is known about what effects of changesin knowledge have on behavior (Taubes, 1996). Therefore, we aimed in this studyto develop and test a causal model addressing the relative ordering of knowledge,attitudes, self-ef� cacy, and osteoporosis preventive behaviors in terms of increasedcalcium intake and weight-bearing exercise.

First, we hypothesized that knowledge would positively predict attitude, self-ef� cacy, calcium intake, and exercise. Second, attitude would positively predict self-ef� cacy, calcium intake, and exercise. Third, self-ef� cacy would positively predictcalcium intake and exercise. Fourth, attitude and self-ef� cacy would mediate theeffect of knowledge on calcium intake and exercise.

THEORETICAL MODEL

Social cognitive theory is used as a theoretical framework to support the theoret-ical model for this study. According to social cognitive theory, cognitive processesare important to attain behavior. Also, procedures based on performance are power-ful in behavior change (Bandura, 1977). A major concept of social cognitive theoryis self-ef� cacy, which is believed to be the single most important characteristic thatdetermines a person’s behavior change (Bandura, 1986). In relation to the theory,two types of expectancies, outcome expectancy and ef� cacy expectancy, indicatepowerful in� uences on behavior. Self-ef� cacy expectations are based on four majorsources of information, including performance accomplishment (successful mastery),vicarious experience, verbal persuasion, and emotional/physiological arousal. In ad-dition, self-ef� cacy expectations can have a signi� cant impact on behavior change.This knowledge can lead to a better understanding of how behavior change can beproduced.

Another psychosocial theory, the health belief model, has been used to identifyfactors related to health-promoting behaviors (Murray & Zentner, 1993). The modelstates that a person’s health-related behavior depends on his or her perception of

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four major domains: the severity of a potential illness, the susceptibility to thatillness, the bene� ts of taking a preventive action, and the barriers to taking thataction (Rosenstock, 1966). According to the health belief model, individuals whohave certain beliefs will be more likely to achieve a behavior (Rosenstock, 1966).The model also explains that “an individual who has appropriate health beliefs tendsto prevent and detect diseases in the asymptomatic stage” (McCorkle, Grant, Frank-Stromborg, & Baird, 1996, p. 215).

Staging

The theoretical model (Figure 1) including four stages is proposed on the ba-sis of social cognitive theory and the health belief model as well as literature. Itwas proposed that knowledge (stage I: knowing) will in� uence health belief atti-tudes (stage II: driving force), which contribute to self-ef� cacy (stage III: engaging/readiness to change), and exercise and calcium intake behaviors (stage IV: changingbehaviors).

The four-stage theoretical model re� ects the premise that preventive behaviors(exercise and calcium intake behaviors) result from the direct and indirect in� uencesof knowledge, attitudes, and self-ef� cacy. Self-ef� cacy is expected to increase withincreasing knowledge directly and indirectly when mediated by one’s health beliefattitude. Therefore, in the model, it is proposed that knowledge directly and indirectlyin� uences preventive behaviors when mediated by attitudes and self-ef� cacy.

Figure 1. Theoretical model: factors in� uencing calcium intake and ex-ercise in young women in Thailand.

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Causal Analysis 367

Outcome Variables

The outcome variables of the theoretical model are preventive behaviors includingcalcium intake and weight-bearing exercise. In this study, preventive behaviors arede� ned as behaviors that will decrease an individual’s risk for osteoporosis. Calciumintake is de� ned as the amount of calcium from food consumed per day (mg/day).Weight-bearing exercises include all types of exercise except for swimming. In thisstudy, weight-bearing exercise is de� ned as the frequency and duration of exerciseperformed by an individual over seven days (minute/week).

Although osteoporosis creates health problems mainly in older women, the eti-ology of osteoporosis largely begins in younger age. Usually, peak bone mass ismaximized by the age of 30 (Recker et al., 1992). Therefore, young women are atargeted group for osteoporosis prevention (Ausenhus, 1988). Weight-bearing exer-cise has been reported to increase peak bone mass in young adults (Frederick &Hawkins, 1992). Inadequate calcium intake is the most important risk factor forosteoporosis (Allen, 1993). If young women maximize their bone density by in-creasing calcium intake and weight-bearing exercise, they can prevent or delay thedevelopment and severity of osteoporosis.

Independent Variable

Knowledge has been de� ned as an awareness or perception of reality acquiredthrough learning or investigation, which is based on factual information (Chinn &Jacobs, 1987). In this study, knowledge is de� ned as an awareness or perceptionof risk factors for osteoporosis and strategies for prevention in terms of increasedcalcium intake and weight-bearing exercise.

Until recently, there were few research studies examining the use of educationalinterventions for osteoporosis prevention in young women. Findings from thesestudies provide support for interventions that focus on education as a way to havea positive impact on increasing knowledge (Sedlak, Doheny, & Jones, 1998, 2000),health belief attitudes (Klohn & Rogers, 1991; Sedlak et al., 1998), and calciumintake and physical activity (Jamal et al., 1999).

Health belief attitude in this study is de� ned as the belief related to osteoporosisand its prevention, including perception of susceptibility to osteoporosis, perceptionof seriousness of developing osteoporosis, bene� ts of and barriers to calcium in-take, bene� ts of and barriers to exercise, and health motivation for preventing thedevelopment of osteoporosis. In the literature, there is evidence to support attitudesand behavior as being highly correlated but no evidence of a causal relationship(Ajzen & Fishbein, 1980; Kim & Hunter, 1993). In this study, the causal nature ofthe relationship was examined.

Self-ef� cacy in this study is de� ned as the individual’s con� dence to performpreventive practices/behaviors in the domains of increased dietary calcium andweight-bearing exercise. Self-ef� cacy has been identi� ed frequently as a powerfulfactor in� uencing behaviors among samples of healthy adults and among adults ofall ages with health problems in the short and long term (Clark, 1996; Conn, 1998;Gillis, 1993; Lawrance & McLeroy, 1986; Plotnikoff , Brez, & Hotz, 2000; Resnick &Spellbring, 2000; Stretcher, DeVillis, Becker, & Rosenstock, 1986). The mediatingeffects of self-ef� cacy have been documented (Gortner & Jenkins, 1990; Rimal,2000; Robertson & Keller, 1992; Sallis, Pinski, Grossman, Patterson, & Nader, 1988).

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For example, in the study by Robertson and Keller (1992), self-ef� cacy is mediatedby health beliefs and exercise adherence, with the causal model explaining 31% ofthe variance in exercise adherence.

The research question addressed by the proposed model was, What is the impactof knowledge about osteoporosis, health belief attitudes, and self-ef� cacy on exerciseand calcium intake behaviors among young college women?

METHODS

Design

An experimental design with one intervention group and one control group wasused to test the theoretical model.

Sample

One hundred women were recruited from a total of 140 young women who wereenrolled in the � rst year of a nursing program in Thailand. Inclusion criteria were(1) the ability to report daily calcium intake or (2) the ability to report amount ofweight-bearing exercise. Participants who had history of urinary tract stones or renaldisease were excluded from the study.

Procedures

Participants were randomly assigned to either intervention or control groups,which included 50 subjects each. Participants in the control group completed thepretest measures at the � rst meeting and completed the posttest measures two weekslater. They were given the opportunity to participate in the osteoporosis educationalprogram after completion of the posttest.

In order to control for cross contamination with the control group, the pretestfor the intervention group was given when the posttest for the control group wascompleted. The intervention group completed the pretest measures and then partici-pated in the educational program developed by the researcher. This program was athree-hour course including instructional materials and a slide presentation, whichconsisted of identi� cation of osteoporosis risk factors, identi� cation of potential con-sequences of osteoporosis, and strategies to prevent osteoporosis, including effectiveexercise and maintenance of the daily calcium requirement. All participants in theintervention group received informational materials with instruction and a demon-stration regarding the use of weight-bearing exercises and had the opportunity toconduct a return demonstration of the speci� c weight-bearing exercises, includingaerobic exercise and jumping rope. Two weeks after the program, posttest measureswere collected to assess osteoporosis speci� c knowledge, health beliefs, self-ef� cacy,and behaviors, including calcium intake and weight-bearing exercise.

Instruments

Knowledge was measured by the modi� ed version of the osteoporosis knowl-edge test (OKT). The OKT (Kim, Horan, Gendler, & Patel, 1991) is a 24-itemquestionnaire that measures knowledge of risk factors and strategies for osteoporo-

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Causal Analysis 369

sis prevention. The OKT has two subscales: OKT calcium and OKT exercise. Scoresrange from 0 (all incorrect) to 24 (all correct). Reliability coef� cients (KR 20) rangedfrom .40 to .86. In the original version, KR 20 ranged from .69 to .72.

Health belief attitude was measured by the 42-item osteoporosis health beliefscale (OHBS; Kim et al., 1991). The questionnaire measures health beliefs relatedto osteoporosis on seven subscales: (1) susceptibility to osteoporosis; (2) seriousnessof developing osteoporosis; (3) bene� ts of calcium intake; (4) bene� ts of exercise;(5) barriers to exercise; (6) barriers to calcium intake; and (7) health motivationfor preventing the development of osteoporosis. The response for each item rangesfrom “strongly disagree” (1) to “strongly agree” (5). Total possible scores range from42 to 210. Reliability coef� cients (Cronbach’s alpha) ranged from .82 to .95, whereasthose of the original scale ranged from .71 to .82. Construct validity was examinedby con� rmatory factor analysis with varimax rotation. In this study, factor analysiscon� rmed the � ve factors explaining 58.4% and 57.3% of variance for exercise andcalcium, respectively. For the original scale, � ve factors explained 52.8% and 49.9%of variance for exercise and calcium, respectively.

Self-ef� cacy was measured by the osteoporosis self-ef� cacy scale (OSES; Horan,Kim, Gendler, Froman, & Patel, 1998), a 21-item scale that measures con� dence inperforming risk reduction behaviors focusing on exercise and dietary calcium intake.In this study, the original version of visual analogue self-ef� cacy scale was modi� edand changed to a continuous scaled measure ranging from 1 to 10. The possible scorefor each item ranges from “not at all con� dent” (1) to “very con� dent” (10). Totalpossible scores range from 21 to 210. Reliability coef� cients (Cronbach’s alpha)ranged from .94 to .96 in this study and from .93 to .94 in the original scale. Factoranalysis con� rmed the two factors, which were related to self-ef� cacy for exerciseand calcium intake, accounting for 78.1% of total variance in the present study and86% in the original scale.

These measures were translated to Thai and revised. A bilingual expert in Englishand Thai con� rmed that the translation was correct. Back translation was performedby another bilingual expert in English and Thai.

Calcium intake was assessed by using the method of 24-hour dietary recall,which is a well-developed measure of average intake (Block, 1982). Daily calciumintake (mg/day) was assessed by a modi� ed detailed three-day food record form.Participants were instructed how to keep an accurate three-day food record. Theimportance of accurate and complete descriptions of meal preparation from thegiven recipes was addressed. All food items and portions were recorded for threedays. At the end of the three-day recording period, they were asked to return therecord to an experienced dietitian for veri� cation of completeness and accuracy.The participants were asked to provide additional information of any unclear fooditem. To increase the accuracy of estimation of size and amount of each food item,food models, measuring cups and spoons, and a face-to-face dietary interview wereused to assist participants with their recall. Using the mean calcium intake fromthree-day records in the study was intended to increase reliability (Buzzard, 1998;Willet, 1998). For data analysis, all food records were coded by food item andamount. The data were then calculated for dietary calcium. The computation ofnutrient data was made by using the computerized food composition analysis package“Nutritionist III” modi� ed for Thai foods by the Institute of Nutrition, MahidolUniversity, Bangkok, Thailand (Institute of Nutrition, 1989). This program has beenused widely to compute nutrient intake in the Thai population.

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Weight-bearing exercise was measured by self-report of the duration, frequency,and type of weight-bearing exercises performed by participants within the past7 days. Exercise data were reported as total minutes per week.

The Human Subjects Review Committee at the University of Washington ap-proved the study. Participation in the study was voluntary. Written informed consentswere obtained.

Data Analysis

The underlying assumptions of causal modeling using path analysis were con-� rmed (Munro, 2001). Analytic strategies consisted of descriptive statistics andregression-based path analysis. Regression analyses were conducted in pretest datain the control group, posttest in the control group, pretest in the intervention group,and posttest in the intervention group. Initially, linear regression was used with thestage II dependent variable regressed on the stage I independent variable to determinethe impact of the independent variable in stage I on the stage II dependent variable.Linear regression was also analyzed between the stage II independent variable andthe stage III dependent variable as well as the stage III independent variable andthe stage IV dependent variables. A set of regressions determined the relative effectof the independent variables on the dependent variables. The order of inclusion ofpredictors was compatible with the causal model, going from knowledge, attitude,and self-ef� cacy to calcium intake and to exercise. Path coef� cients and R2 statisticswere considered statistically signi� cant at the p · :05 level (Pedhazur, 1982). Theunit of analysis was the individual.

RESULTS

Description of the Sample

One hundred ten young women agreed to participate. Ten participants did notcompletely � ll out the instruments and dropped out of the study. These resultsrepresent 100 participants. The mean age was 18.5 years (SD D 0:6), with age rangefrom 17 to 21 years. All participants were nondrinkers and nonsmokers.

Model Testing

Table 1 reports the correlation matrix among dependent variables, mediatingvariables, and the independent variable.

Health belief attitudes impacted on self-ef� cacy in the control group at pretestand posttest. The beta coef� cient was .49 and .43 and predictive power was .21and .14, respectively. The regression analysis determined the contribution of healthbelief attitudes to self-ef� cacy. The order of inclusion of predictors was knowledge,attitude, self-ef� cacy, calcium intake, and weight-bearing exercise. Calcium intakeand exercise were not predicted by any independent variable.

In the intervention group at time 1 (before intervention), calcium intake behaviorwas directly predicted by knowledge (¯ D :39, R2 D :12), and self-ef� cacy waspredicted by attitudes (¯ D :41), whereas attitudes tended to be predicted byknowledge (p-value D .054). No independent variables were found to be a predictorfor exercise. At time 2 (after intervention; Figure 2), calcium intake was directlypredicted by self-ef� cacy (¯ D :38, p-value < .05) and a trend toward being

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Table 1. Correlation matrix of variables in the path model ofexercise and calcium behaviors

Variables 1Ca intake Exercise Knowledge Attitude Self-ef� cacy

Ca intake 1.0 0.04 0.24¤ 0.01 0.06Exercise 1.0 0.16 0.19 0.21¤

Knowledge 1.0 0.17 0.14Attitude 1.0 0.47¤¤

Self-ef� cacy 1.0

¤Correlation is signi� cant at the 0.05 level.¤¤Correlation is signi� cant at the 0.01 level.1Ca D Calcium.

predicted by knowledge (¯ D :30, p-value D .059). However, calcium intakewas indirectly predicted by knowledge through health belief attitudes and self-ef� cacy. Self-ef� cacy predicted calcium intake. Attitudes predicted calcium intake.The predictor of calcium intake was self-ef� cacy, which accounted for 30% of thevariance. Exercise behavior was predicted directly by knowledge (¯ D :62) andself-ef� cacy (¯ D :36). Moreover, knowledge indirectly predicted weight-bearingexercise when mediated by attitudes and self-ef� cacy. Self-ef� cacy predicted exercisein a positive direction, whereas attitudes predicted exercise in the opposite direction.Weight-bearing exercise was predicted by knowledge, attitudes, and self-ef� cacy,which accounted for 45% of the variance. The predictive power that knowledge,attitudes, and self-ef� cacy contributed to exercise was slightly better than thosecontributed to calcium intake; however, overall adjusted R2 for the model wasstatistically signi� cant.

DISCUSSION

The path models derived from data after the intervention program in the interven-tion group support the effectiveness of the program focused on increasing knowledgeand enhancing self-ef� cacy. The lack of direct prediction from attitude, re� ected inthe model, is probably due to the low predictive power of attitude, which is a keycomponent of the health belief model. According to the literature, the health be-lief model is limited to predicting behaviors that are related to attitudes and beliefs(Janz & Becker, 1984; Rosenstock, 1990); therefore, it may not be appropriate for theapplication to other cultures. However, our � nding is consistent with Kasper, Peter-son, Allegrante, Galsworthy, and Gutin (1994), which indicated that young women’sbeliefs about osteoporosis did not affect their behaviors.

The causal relationship of the control group before the intervention is consistentwith that of after the intervention, going from attitudes to self-ef� cacy, which re� ectsno change of predictive direction. The outcome variables including calcium intakebehavior and weight-bearing exercise cannot be predicted by any of the independentvariables. The causal relationship before the intervention program in the interventiongroup is different from that after the intervention in that there is a more complexmodel developed in the latter model. In this model (Figure 2), calcium intake wasdirectly predicted by self-ef� cacy. Although the relationship was not statisticallysigni� cant, there is a trend of a causal relationship between knowledge and calcium

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Causal Analysis 373

intake. However, knowledge has a more indirect predictive power for calcium intakewhen mediated by attitudes and self-ef� cacy.

At time 2 (after the intervention), attitude negatively predicted exercise behavior.A positive prediction was supported from attitude to exercise through self-ef� cacy.This can be explained by the fact that young Thai women did not always changetheir exercise behavior, although they had more health belief attitudes following theintervention. Another explanation in terms of health behaviors is that they mayrespond differently than the general public, since they are already interested inhealth issues. However, the intervention was effective in terms of increasing theirself-ef� cacy, which mediated a positive casual relationship between attitudes andexercise behavior. Therefore, exercise was positively and indirectly predicted byattitudes when mediated by self-ef� cacy.

The � nal model supports the hypotheses that knowledge made statistically sig-ni� cant contributions to exercise and calcium intake behaviors both directly andindirectly, when mediated by self-ef� cacy. In this study, knowledge was supportedto be the independent predictor of calcium intake and exercise behaviors, which arethe outcome variables. Ali (1996) also found that knowledge was a predictor forthe behavior of calcium intake among college women, with an explanatory power at36% of the variance of total calcium intake. These � ndings suggest that engaging inpreventive behaviors is dependent on having adequate knowledge. A linear modelsuggests that increasing knowledge will change behavior (Valdiserri, West, Moore,Darrow, & Hinman, 1992). However, a limitation in the model is that it ignores theindividual’s environment and the concept of self-ef� cacy, which can have a strongeffect on behaviors (Valdiserri et al., 1992).

Self-ef� cacy has been reported to be a signi� cant predictor of exercise in collegestudents (Terry & O’Leary, 1995). However, in this study self-ef� cacy mediated theassociation between knowledge and behaviors, which is consistent with a recent studyby Rimal (2000). In Rimal’s study, knowledge was highly correlated with behavioramong participants with high self-ef� cacy, compared to those with low self-ef� cacy.Moreover, the correlation between knowledge and behavior increased among thosewith greater self-ef� cacy and decreased among those with lesser self-ef� cacy.

Although research addressing the comparative sequence of knowledge, attitudes,and practices (KAP) in behavior change has been conducted for decades (Berelson,1966), the effect of knowledge on behavior is still controversial. An argument onthis issue is that it is not necessarily true that individuals who are knowledgeableof a healthy behavior will engage in that behavior. Therefore, only giving an in-dividual knowledge of a healthy behavior does not ensure they will change theirbehavior (Ali & Bennett, 1992). Knowledge alone is not enough to effect behaviorchange. Currently, many education programs focus primarily on knowledge. How-ever, enhancing self-ef� cacy can facilitate the link between knowledge and behav-iors by persuading individuals to accomplish the requisite behaviors within theircontrol. Self-ef� cacy should be enhanced by targeting its sources, which accordingto Bandura (1977) are: verbal persuasion, performance accomplishment, vicariousperformance, and physiological arousal.

The � ndings of this study support the importance of knowledge and self-ef� cacy.The relationship of knowledge and self-ef� cacy found in this study suggests thatknowledge of adequate calcium intake and exercise to prevent osteoporosis is a strongdeterminant of young women’s judgment of their ability to perform the behaviors.These � ndings are consistent with Pender (1987), who described a healthy lifestyle

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as a complementary component of health-promoting behaviors, which are in� uencedby many factors including knowledge. Since knowledge has shown to have a majorimpact on behavior change (Drugay, 1997; Liscum, 1992), improving knowledgecan lead to engaging in preventive behaviors.

In this study, key intervention components were identi� ed. This predictive modelsuggests the design of interventions to increase young women’s knowledge of risksfor osteoporosis, enhance self-ef� cacy for preventive behaviors, which will result inimproved preventive behaviors.

Strengths and Limitations

A causal model based on theory-based intervention study with experimental de-sign developed and tested is a strength in this study. Also, implications for inter-vention programs for osteoporosis prevention are provided. However, the study haslimitations. First, the sample was homogeneous and small, which limits generaliz-ability of the study � ndings to Thai women who are not nursing students. Second, theself-reported exercise measures were not validated with objective measures, such asaccelerometers that measure movement. Third, the instruments were slightly mod-i� ed from the original versions due to differences in culture. During the processof translation and back translation, some items could not be directly translated,such as “When you think about osteoporosis you get depressed” does not have thesame meaning as “You feel anxious when thinking of osteoporosis.” And, last, allparticipants were nursing students, who may respond differently than the generalpopulation.

Recommendations for Further Study

The � ndings suggest that the development of future models to be tested shouldinclude knowledge and self-ef� cacy as major components. Exercise measured inthis study included diverse forms of weight-bearing exercises. Future research couldexamine speci� c forms of exercise such as jumping rope and aerobic dance. Sinceself-ef� cacy expectations are behavior speci� c, the predictive power of the modelcould be increased by emphasizing speci� c forms of exercise (Bandura, 1986). Themodel developed and tested in this study focused on two components of Bandura’smodel of behavior: internal factors (speci� cally cognitive constructs) and behavior.Future research could examine environmental effects on internal factors and behav-ior. In addition, studies using a longitudinal design could be conducted to re� ectadherence to the preventive behaviors.

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