This study was conducted with 175 French-speaking Swiss male athletes practicing bodybuilding who met the following eligibility criteria: (a) minimum age of 16 years, (b) minimum of 3 h of physical training per week, and (c) minimum of 3 years of bodybuilding. The ethics committees of the University of Teacher Education of the State of Vaud (Switzerland) and the University of Nice Sophia-Antipolis (France) approved the protocol design and the study. Data were collected over 6 months and participants were recruited in a social network or in gyms. Written informed consent was obtained from the participants prior to their participation (or their parents in the case of minors). Online survey completion did not exceed more than 20 min and responses to all questions were obligatory; there were no missing data. Participants were informed beforehand that the survey was not a test (i.e., there were no right or wrong answers) and that all responses would be used for research purposes only.

Participation was entirely voluntary and full confidentiality was guaranteed. Authors collected information about nationality in order to ensure that participants were French speakers. Participants answered each item with a Likert scale ranging from 1 (not at all) to 6 (absolutely). They were asked to rate several reasons pertaining to four regulation styles varying in the degree of autonomy on a continuum ranging from high to low autonomy: extrinsic regulation, introjected regulation, identified regulation, and intrinsic regulation. Extrinsic regulation is the least autonomous form of motivation, while intrinsic motivation is the most autonomous. Autonomous motivation was represented by eight items corresponding to intrinsic regulation (four items; e.g., I do sports because I think exercise is fun) and identified regulation (four items; e.g., I do sports because I value the benefits of exercise). Controlled motivation was represented by seven items corresponding to extrinsic regulation (four items; e.g., I do sports because other people say I should) and introjected regulation (three items; e.g., I do sports because I feel guilty when I don’t exercise).

A 6-point Likert scale from 1 (not at all) to 6 (absolutely) was used. For each scale, the CFA was computed and Cronbach’s alphas were performed to verify the internal consistency of each construct. Four items related to the perceived benefits of gaining muscle mass were used (e.g., I think I would be more self-confident if I had more muscle mass). Subjective norm related to gaining muscle mass was measured through four items (e.g., My peers approve of me trying to increase my muscle mass). Five items related to perceived behavioral control related to gaining muscle mass were used (e.g., I feel able to do intensive strength training). 07. A satisfactory Cronbach’s alpha value of .76 was obtained for this subscale. The measure of the intention to gain muscle mass was composed of three items (e.g., I intend to gain muscle mass). "muscularity body dissatisfaction" and "muscularity behaviors". The items were answered with a Likert scale from 1 (not at all) to 6 (absolutely).

This study included several types of analysis. First, confirmatory factor Titan Rise analyses (CFA) were performed to verify the validity of the scales. Second, a series of path analyses was performed to test the hypothetical model. "totally free" model is almost always significant, even for well-fitting models, making it an inadequate basis for model evaluation. Modification indices were used to flag fixed parameters in the model that would make a significant change in the goodness-of-fit chi-square value if freed, and the likelihood-ratio test based on the goodness-of-fit chi-square was used to identify misspecifications in the constrained models from the invariance analyses relative to the baseline model. Seven factors were incorporated: autonomous motivation, controlled motivation, attitude, subjective norm, perceived behavioral control, intention to gain muscle mass, and DM. In order to define the scale of the factors and to ensure that the model was properly identified, one indicator for each factor was arbitrarily set to the value of one.

In addition, all the latent factors were freely correlated, as is the norm in path analysis. Because χ2 difference tests cannot be legitimately performed on non-nested models, Akaike’s information criterion (AIC) and the expected cross validation index (ECVI) were used. The AIC and ECVI were not normed on a zero to one scale. Methods of multiple mediation were adopted, and the different effects and their corresponding 95% CIs were calculated to estimate both total and indirect effects for the multiple mediator models, using bootstrapping and providing bias-corrected 95% CIs. The series of path analysis tests began with the first model that incorporated the seven factors (i.e., autonomous motivation, controlled motivation, attitude, subjective norm, perceived behavioral control, intention to gain muscle mass, and DM) and all the links were tested as the hypothetical model. DM; from controlled motivation to perceived behavioral control; from subjective norm to intention to gain muscle mass; from controlled motivation to intention to gain muscle mass; and from perceived behavioral control to DM. The third model was also composed of the seven factors and all relationships that were significant in the previous model. The attitude error Titan Rise Male Enhancement and the perceived behavioral control error were related to have a better fit index for the final model. RMSEA, TLI, and CFI were acceptable, and the probability value (p) was below .05.