Prevalence and social-cognitive determinants of the use of performance enhancing substances by Portuguese gymgoers

Background: The use of performance-enhancing substances (PES) occurs among gym goers, which is seen as a public health concern. The aim of this study is to investigate the extent of PES use and the social-cognitive determinants whichinfluence the intention to use these substances among gym goers, according to the Theory of Planned Behaviour.Methods: A convenience sample of Portuguese gym goers (n = 453; 61,3% female; 38,7% male) completed an anonymous webbased survey about beliefs, attitudes, social influences and intentions towards use of PES as well as self-reported PESuse. A two-step approach to maximum likelihood, structural equation modelling, multigroup analysis and t-test with the Welch correction for heteroskedastic variances were performed using IBM SPSS/AMOS 24.0.Results: 11.01% of the participants reported PES use. At the structural level, results support attitudes (b = 0.21; p < 0.001), beliefs (b = 0.35, p< 0.001) and subjective norms in predicting intentions to PES use in gym goers with subjective norms (b = 0.50; p <0.001) being its strongest predictor. Moreover, results showed a significant association self-reported PES use and intentions to use (b = 0.66, pp < 0.001). The predictive model was invariant across gender; however, compared to males, females believed less in the performance enhancing effects of PES, were less prone to the influence of significant others and had weaker intentions to use these substances.Conclusion: Preventive interventions should focus on influencing subjective norms, alongside to beliefs and attitudes towards PES use as these variables influence the intention to use PES in this particular population.