Are nutritional supplements a gateway to doping use in competitive team sports? The roles of achievement goals and motivational regulations

Objectives The study investigated the moderating role of achievement goals and motivation regulations on the association between self-reported nutritional supplement (NS) use, doping likelihood, and self-reported doping behaviour among competitive athletes. Method Four hundred and ninety seven competitive team sport athletes (64% males;M age = 23.54 years, SD = 5.75) completed anonymous questionnaires measuring self-reported use of prohibited substances and licit NS; beliefs about the "gateway" function of NS; achievement goals; and motivational regulations. Results Hierarchical linear regression analysis showed that self-reported doping was associated (Adjusted R2 = 33%) with NS use, a stronger belief that NS use acts as a gateway to doping, amotivation, controlled motivation, mastery approach, and performance avoidance goals. Higher likelihood to use doping substances in the future was associated (Adjusted R2 = 41.7%) with current NS use, stronger belief that NS act as a gateway to doping, autonomous motivation, and performance avoidance goals. A series of moderated regression analyses showed that NS use significantly interacted with mastery approach, mastery avoidance, performance avoidance goals, autonomous motivation controlled motivation, and with amotivation in predicting self-reported doping. Finally, NS use significantly interacted with mastery approach goals, performance avoidance goals, and controlled motivation in predicting future doping likelihood. Conclusions Achievement goals and motivational regulations are differentially associated with both doping likelihood and self-reported doping, and may account for the observed association between self-reported NS use and doping substances; thus, providing an alternative explanation to the "gateway hypothesis" that emphasizes the role of motivation.