Background: Road traffic injuries (RTIs) are one of the most critical factors that endanger human health. More specifically, head and neck injuries are the main causes of deaths and disabilities among motorcyclists. This study aimed to investigate the predictive factors of helmet use behavior among motorcyclists based on the theory of planned behavior (TPB). Study Design: This study followed the cross-sectional design. Methods: This study was conducted on randomly selected 730 motorcyclist employees in Qom, Iran, in 2021. The data collection tool was a self-administered researcher-made questionnaire, including items on demographic characteristics, history of RTIs, and constructs of TPB. Data were analyzed using descriptive summary statistics, analysis of variance, independent samples t test, Pearson correlation coefficient, and structural equation modeling (SEM). Results: In this study, only 9.8% of the participants reported that they always used a helmet while riding a motorcycle. About 60% reported a history of a motorcycle crash, and 11.5% had a history of head injuries. The direct effect of attitude, subjective norms, and perceived behavioral control on the intention to use a helmet were statistically significant, explaining 59% of the variation in behavioral intention (intention to use a helmet) (R2=0.59). Moreover, perceived behavioral control and behavioral intention had significant effects on helmet use behavior (R2=0.26). Conclusion: The prevalence of helmet use among the studied population was very low. Moreover, TPB was useful in identifying the determinants of behavior and especially behavioral intention of helmet use among motorcyclists.

Background: Athletes’ use of androgenic-anabolic steroids (AASs) is a significant health problem. This study aimed to determine factors associated with AAS in male bodybuilders by applying the theory of planned behavior (TPB). Methods: Using a multistage random sampling procedure, this descriptive-analytical cross-sectional study was performed on 429 athletes participating in gyms in Qom, Iran, in 2019. The data collection tool was a questionnaire, including demographic information and questions related to TPB constructs. Data were analyzed by descriptive statistics, Chi-square test, logistic regression, and linear regression using SPSS software, version 16. Results: The results demonstrated that 188 (48.2%) athletes had a history of AAS use. The attitude (β=0.39), subjective norm (β=0.26), and perceived behavioral control (β=-0.36) predicted 38% of the variance of intention to AAS use. Further, behavioral intention was the statistically significant predictor of AAS use among the studied athletes (OR=0.83, 95% CI: 0.78-0.87). Variables such as having friends (OR=2.06, 95% CI: 1.28-3.30) or a sports coach using AAS (OR=3.1, 95% CI: 1.58-6.42) and having a history of supplementation use (OR=5.8, 95% CI: 2.65-12.8), along with age (OR=4.3, 95% CI: 0.35-53.6) had a significantly predictive role in using AAS. Conclusion: The findings revealed that nearly half of the studied athletes had a history of using AAS and supplements. TPB is applicable to identify the determinants of beliefs, intention, and behavior to use AAS among athletes. These findings can be useful in designing appropriate programs to prevent AAS use.