IntroductionUnlike sport activities conducted in Physical Education classes, organized competitive sports are freely chosen by children, and certain commitment on the part of the child is needed. Within this context of skills and achievements, motivational factors play a key role in the long-term effects of sport participation on psychosocial development (Garcia-Mas et al., 2011). The physical and psychological well-being of an athlete is not automatically promoted (Duda & Balaguer, 2007; Quested & Duda, 2011), rather it depends upon the social settings in which it develops and is, in turn, closely linked to the role played by the coach and significant others (Roberts & Treasure, 2012; SanchezMiguel, Leo, Sanchez-Oliva, Amado, & Garcia-Calvo, 2013). The importance ofthe coach and his influence on athletes has been widely addressed (Sousa, Cruz, Torregrosa, Vilches, & Viladrich, 2006). According to the approach adopted by the trainer, an athlete's satisfaction with and adherence to a given sport may be enhanced or compromised, and this may impact self-motivation, level of involvement and level of commitment (MartinAlbo, Nunez, & Navarro, 2003 ; Ortiz, Arriaza, & Jeria, 2011; Weiss, 2015). The consequence of all this is that the sport environment becomes a setting of socializing influences playing a pivotal role in forming a child's personal character (Torregrosa et al., 2007).According to Castillo, Balaguer, Duda and Garcia (2004), the social cognitive theory of goal orientations (Nicholls, 1989) is a conceptual framework that helps our understanding of the motives and processes whereby children take up a sports activity or abandon such an activity. Achievement goal theory tries to identify the different dispositional and environmental factors that affect achievement motivation in an athlete.According to this construct, dispositional factors reflect the criterion used by athletes to measure their competence level and according to which they subjectively define success and failure. Situational factors refer to the signals emitted by persons such as relatives, friends, or coach that are perceived by the athlete and through which are defined the keys to success or failure, described by Ames (1992) as the motivational climate. Thus, depending on how the context is perceived by the athlete, a competitive, performing, ego-orientated or a mastery, task-orientated motivational climate is created (Ames, 1992; Newton, Duda, & Yin, 2000; Nicholls, 1989). It has been shown that the perception of a mastery motivational climate favors sport performance, enjoyment, satisfaction (Donkers, Martin, Paradis, & Anderson, 2015; Sousa, Torregrosa, Viladrich, Villamarin, & Cruz, 2007), commitment (Leo, Sanchez, Sanchez, Amado, & Garcia, 2009; Lukwu & Lujan, 2011; Sanchez-Oliva, Leo, GonzalezPonce, Chamorro, & Garcia-Calvo, 2012) and psychological well-being by improving confidence and self-esteem and by reducing anxiety (Balaguer, Duda, Atienza, & Mayo, 2002). In contrast, a climate striving to improve performance produces less psychological well-being, greater anxiety relative to performance and less satisfaction with the sport environment (Balaguer, Duda, & Crespo, 1999).However, from a perspective of disposition, both goal orientations rather than being dichotomous show an orthogonal behavior (Nicholls, 1989). In other words, as explained by Cervello, Escarti and Balague (1999), when assessing motivational orientation we may find athletes simultaneously orientated towards varying intensities of both mastery and ego. Hence, athletes may vary their dispositional goal orientations according to their socializing experiences in the sport context (Castillo, Duda, Alvarez, Merce, & Balaguer, 2011; Gomez-Lopez, Granero-Gallegos, Baena-Extremera, & Abraldes, 2014), as is the case of the motivational climate (Ames, 1992) set by the trainer.Although such variations exist, this has not been reflected in most studies, which have concluded that if trainers wish to potentiate the greater well-being of their athletes, they should pursue a task-involved motivational climate that will orient players towards adopting mastery goals in their sport and at all costs avoid an ego-based motivational environment. …