Qom University of Medical Sciences Journal

Introduction
Osteoporosis is one of the major problems of the healthcare system. Due to the increase in life expectancy, the incidence of osteoporosis is gradually increasing, making it a significant concern for public health [1, 2]. This disease has been referred to as the silent disease of the century due to its silent onset [3, 4]. The prevention of osteoporosis and subsequent fractures has been the primary goal for many healthcare providers, especially dietitians [5, 6]. Nearly 75 million people in Europe, Japan, and America are suffering from this disease [7]. 
Approximately 70% of women and 50% of men have osteoporosis or decreased bone mass [8], and about 200 million women worldwide have osteoporosis [9, 10]. One out of every three women is exposed to fractures caused by osteoporosis [11]. Among Iranian women, the prevalence of osteoporosis in the femur and spine is between 6% and 34.4% [12, 13]. Modifiable risk factors include unhealthy lifestyle, such as lack of calcium and vitamin D in the diet, insufficient exposure to sunlight, insufficient exercise, smoking, and alcohol consumption, and non-modifiable risk factors include age, sex, and heredity [14-16]. Pender’s model is a comprehensive and predictive framework for health promotion behaviors that provides a theoretical basis for identifying effective factors in these behaviors [23, 24]. The behavioral outcomes are the ultimate goal of the health promotion model [25]. Therefore, considering the importance of prevention, the risk faced by women and girls, and the limited studies utilizing Pender’s health promotion model, the present study aims to investigate the determinants of physical activity for the prevention of osteoporosis in women aged 15 to 49 years who refer to the comprehensive health service centers in Arak City based on Pender’s health promotion model in 2023. 
Methods
The present cross-sectional, descriptive-analytical study was conducted to investigate the determinants of physical activity in the prevention of osteoporosis in 250 women aged 15-49 years who were referred to comprehensive health service centers in Arak City in 2023. Sampling was done using a multi-stage random sampling method. 
The required sample size for the study, considering the first type error of 5%, d=0.5, and the standard deviation of the behavioral outcome structure score of 3.7, was estimated to be 250 individuals. Criteria for inclusion in the study included having Iranian citizenship, possessing an electronic health record at the health centers of Arak City, and being literate, while non-cooperation in completing the questionnaire and suffering from secondary osteoporosis were criteria for exclusion. 
In the present study, a researcher-made questionnaire was used. The questionnaire had three parts, including demographic information, questions related to the constructs of the health promotion model, and the International Physical Activity Questionnaire to measure physical activity behavior. The content validity ratio and content validity index were 0.86 and 0.89, respectively. 
Results
The results showed that 43.2% of the participants were in the age range of 26 to 35 years, and more than half of them (58.8%) were housewives. Most cases were married (72.2%) and had a university education (68.4%). The results of the chi-square test showed a significant relationship between occupation and physical activity among demographic characteristics (Table 1). Also, 48% of the participants had light physical activity, and only 4.4% had intense physical activity. Regarding the constructs of Pender’s model, the construct of perceived benefits showed the highest mean, and the construct of negative feelings toward physical activity behavior showed the lowest mean score compared to other constructs.
The results of multiple linear regression indicated that, after accounting for influential demographic factors such as income level, number of children, and marital status, the constructs of perceived benefits (β=0.20, P=0.006) and commitment to the action plan (β=0.38, P=0.001) had a direct and significant relationship with physical activity among the participants. This implies that for each unit increase in perceived benefits, there is a corresponding 20% increase in physical activity, while each unit increase in commitment to the action plan results in a 38% increase in physical activity score. Overall, the constructs of Pender’s health promotion model predicted 27% of the changes in physical activity among the participants.
Conclusion
The results of the present study showed that Pender’s health promotion model was somewhat predictive of physical activity, and perceived benefits and commitment to action had a significant relationship with physical activity. Accordingly, individuals who perceived greater benefits from physical activity and demonstrated higher commitment to engaging in physical activity tended to have more physical activity. Given that the level of physical activity among the participants was not optimal, it is recommended to design an educational program that highlights the benefits of exercise and physical activity, as well as provides strategies for maintaining this behavior. Also, it is recommended to use more comprehensive models to investigate other effective determining factors influencing physical activity levels in people’s environments.
Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of Qom University of Medical Sciences, Qom, Iran (Code: IR.MUQ.REC.1402.181). All participants were informed about the study’s objectives and methods, assured of the confidentiality of their information, and were free to withdraw from the study at any time.
Funding
This study received financial support from Qom University of Medical Sciences, Qom, Iran.
Authors contributions
Conceptualization, methodology, project management, and financing: Akbar Ahmadi, Ahmad Rahbar, and Zabihollah Qarlipour;  Literature review: Akbar Ahmadi, Ahmad Rahbar, Maryam Barati, Ehsan Wasali Monfared, and Abolfazl Mohammad Beigi; Data analysis and interpretation: Akbar Ahmadi, Abolfazl Mohammad Beigi, and Siamak Mohebbi; Supervision and management: Akbar Ahmadi, Ahmad Rahbar, Zabihollah Qarlipour; Review, editing and final approval: Siamak Mohebbi, Ahmad Rahbar, Zabihollah Qarlipour, and Akbar Ahmadi.
Conflicts of interest
The authors declared no conflict of interest.
Acknowledgements
The authors express their gratitude to the Research and Technology Vice-Chancellor of Qom University of Medical Sciences for the approval and financial support of the study. The authors would like to thank Arak University of Medical Sciences for their cooperation in implementing the research project in health centers and bases.