Data Collection and Procedure Motivational variables Behavioural regulation during exercise. The Spanish version of Behavioural Regulation during Exercise Questionnaire was used. This questionnaire allows to evaluate the type of motivational regulation related to physical exercise, and consists in 23 items distributed in three dimensions, based on the established distinction in the SDT between autonomous motivation, controlled motivation and demotivation. Autonomous motivation was calculated using the mean score of intrinsic regulation (e.g. "Because I think that exercise is fun"), integrated regulation (e.g. "Because I believe that physical exercise is consistent with my values") and identified regulation (e.g. "I value the benefits of exercise"). Each of these regulations was composed of 4 items, except for the identified regulations which was composed of 3 items. Controlled motivation was calculated using the mean score of introjected regulation (e.g. "I feel guilty when I don't exercise") and external regulation (e.g. "I feel under pressure from my friends/family to exercise") with 4 items each. Demotivation (e.g. "I don't see why I should have to exercise") was also calculated using 4 items. Previous research in the physical activity and health context demonstrated the internal reliability of the instrument.