Knowledge and manipulation of these variables, can therefore contribute to individuals who practice physical exercise optimising their performance, and so enhance their possibilities of achieving better results or fitness and reduce the levels of variables that might affect their continuing to practice sport and physical exercise, in the medium and long term. Psychological variables of importance intervene in all areas of study pertaining to physical activity as they affect the adaptation process toward wellbeing: persistence ( Sheard & Golby, 2010 García-Calvo, Sánchez Miguel, Leo Marcos, Sánchez Oliva, & Amado, 2011), selfefficacy and attention ( Infante, Goñi, & Villarroel, 2011), stress and anxiety ( ), moods ( Fry et al., 2012), self-control and selfregulation ( Vieira et al., 2013), sociability ( Boyd, Kim, Ensari, & Yin, 2014 Esnaola & Revuelta, 2009), interpersonal skills ( Chen, 2001), self-confidence ( Ríes, Castañeda, Campos, & Del Castillo, 2012), or emotional adjustment ( Carver & Scheier, 2012). Relating physical or sports activity to physical and mental wellbeing is an area of great interest for researchers, and there is a growing number of papers on the subject. Finally, as for the differences between gender, we have found differences in favour of males in physical ability, physical condition, physical attractive, strength, physical self-concept, general self-concept, perceived value, perceived difficulty, and expectation of success. Likewise, we have found significant correlations among the scales it is to say, people who are perceived well in the general, physical self-concept and the specific subdomains, have a high perceived value of the physical activity, have an expectation of success and perceive with minor difficulty the physical activity.

The results indicate that the active people (those who practise some physical activity more than two days a week) have better perceptions than the inactive people in the physical ability, physical condition, strength, general physical self-concept and general self-concept, having in addition better expectations of success in the physical activities. The sample consists of 300 teenagers between 12 and 24 years, with an average of 18.64 years. The aim of this study has been to analyze the relations among the physical self-concept, the expectations of success, the perceived value and the difficulty perceived of the physical activity. Finalmente, en cuanto a las diferencias entre sexos, los varones se perciben mejor que las mujeres en el autoconcepto físico y sus dominios específicos, valoran más positivamente y perciben con menor dificultad las actividades físicas, y tienen unas expectativas de éxito más elevadas para las futuras actividades físicas. Asimismo, se han encontrado correlaciones significativas entre las escalas es decir, las personas que se perciben bien en el autoconcepto general, el autoconcepto físico y los subdominios específicos, tienen un valor percibido de la actividad física alta, tienen una expectativa o rendimiento esperado positivo y perciben con menor dificultad la actividad física. Los resultados indican que las personas activas (los que practican alguna actividad física más de dos días a la semana) se perciben mejor que las personas inactivas en la habilidad física, condición física, fuerza, autoconcepto físico general y autoconcepto general, teniendo además mejores expectativas de éxito en las actividades físicas. La muestra se compone de 300 adolescentes entre los 12 y 24 años, con una media de 18.64 años. El objetivo de este estudio ha sido analizar las relaciones entre el autoconcepto físico, las expectativas de éxito, el valor percibido y la dificultad percibida de la actividad física.

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