Deci and Ryan (1985) described the study of motivation as the exploration of the energy and direction of behavior (p. 3), and an adequate theory of motivation must therefore take into account both the innate needs of the organism (i.e. those which must be satisfied for the organism to remain healthy) and those which are acquired by interactions with the environment (Deci, 1985). Cognitive evaluation theory (CET), a subtheory of self-determination theory, addresses the effects of extrinsic motivation on an individual's intrinsic motivation. CET focuses on two fundamental needs, perceived competence and autonomy, subdimensions of intrinsic motivation, which are enriched or reduced depending on the environment and social factors. Perceived competence accompanied by a sense of autonomy has been shown to have a positive impact on intrinsic motivation (Deci and Ryan, 2000). Based on research, CET has shown that extrinsic rewards can undermine a person's intrinsic motivation and shift a person's motivation from internal to external (Deci, 1971; Lepper, Greene, & Nisbett , 1973. But does the same theory apply to individuals who are intrinsically motivated who participate in sports Research has demonstrated that participation in exercise tends to be more extrinsically motivated than participation in. a sport, but that the more autonomous forms of regulation are important for maintaining activity levels of both over time (Ryan & Deci, 2007). intrinsic (e.g., Deci, 1971; Harackiewicz, 1979), many environmental and interpersonal factors (e.g., rewards, coaches' behaviors) can affect athletes. ' feelings of ...... middle of article ......Deci, EL (2007). In M. Hagger & N. Chatzisarantis (Eds.), Intrinsic motivation and self-determination in exercise. and sports. Champaign, IL: Human Kinetics. Harackiewicz, J.M. (1979). The effects of reward contingency and performance feedback on intrinsic motivation. Journal of Personality and Social Psychology, 37, 1352-1363. Lepper, M.K., Greene, D., & Nisbett, R. (1973). Undermining children's intrinsic interest with extrinsic reward: A test of the “overjustification” hypothesis. Journal of Personality and Social Psychology, 28, 129–137Pelletier, LG, Fortier, MS, Vallerand, RJ, Tuson, KM, Brière, NM and Blais, MR (1995). Towards a new measure of intrinsic motivation, extrinsic motivation and amotivation in sport: the sports motivation scale (SMS). Journal of Sport and Exercise Psychology, 17, 35-53.