The mental health problems of Chinese adolescents are becoming more and more serious. According to the Report on the Development of Chinese National Mental Health (2021–2022) released by the Chinese Academy of Sciences, 14.8% of adolescents have different degrees of depression risk(Fu & Zhang, 2021). Adolescents are a group with high risk of mental illness, and their mental health education has been highly concerned by the state, schools, society and families. According to the view of positive psychology, helping adolescents form good self-cognition and construct positive psychological qualities will enable individuals to avoid and overcome problems encountered in the process of development and have the ability to "actively" obtain well-being. Subjective Well-Being (SWB) is an evaluation of one's own quality of life according to one's personal standards, and a comprehensive index to measure one's quality of life and mental health(E. & A., 1984). It usually includes three dimensions: satisfaction, positive emotion and negative emotion. There is no doubt that physical exercise can promote individuals to produce positive psychological benefits, and the relationship between physical exercise and subjective well-being has attracted much attention from researchers. As an important factor affecting individual exercise participation, exercise goal content can explain and predict individual health level and exercise behavior(Li, 2015, Xiang, 2014). Previous studies have confirmed that exercise motivation and psychological need satisfaction play a single mediating role in the relationship between exercise goal content and subjective well-being(Li, 2015, Xiang, 2014, Gunnell & Crocker et al., 2014). However, when exercise motivation and psychological need satisfaction are both mediating variables, the chain effect of them on the relationship between goal content and well-being remains to be further investigated(Xiang, 2014, Sebire & Standage et al., 2009). However, relative intrinsic goal index failed to reflect the mechanism of intrinsic goal pursuit and extrinsic goal pursuit affecting adolescent subjective well-being. It has certain practical guiding significance for improving teenagers' subjective well-being.
Goal Content Theory(GCT), as one of the six sub-theories of Self-Determination Theory (SDT), usually explores how different goal contents (intrinsic goals and extrinsic goals) affect individual well-being and behavioral outcomes(Ryan & Deci, 2017, Sebire et al., 2009). The intrinsic goal pursuit can enhance the individual's well-being and psychological adaptability, and help to promote mental health, while the extrinsic goal pursuit may bring negative emotions, reduce well-being or have nothing to do with well-being, resulting in psychological maladjustment(Zhang & Zhang et al., 2017, Ye & Lu et al., 2019). The exercise goals that individuals set for their own internal development are internal exercise goals, such as social relations, skill development and health management, and the exercise goals set for external recognition are external exercise goals, such as body image and social praise(Sebire & Standage et al., 2008). The exercisers with internal exercise goals (e.g., enjoyment or competition) are more inclined to engage in social exercise through fitness techniques to improve their well-being level, while the exercisers with external exercise goals (e.g., image) are negatively related to the social characteristics of exercise, which is not conducive to the development of individual well-being level(James & Deane et al., 2019).
SDT postulates that humans have three basic psychological needs: Autonomy, Competence, and Relatedness(Ryan & Deci, 2017). The individual's need for autonomy reflects the need to experience self-approval and voluntary activities; the need for competence implies the need to effectively deal with one's environment; and the need for relatedness includes experiencing a sense of belonging and attachment to others(Ryan & Deci, 2017). Basic psychological needs are one of the influencing mechanisms of goal content. Different types of goals will promote or hinder the satisfaction of psychological needs, and the satisfaction degree of psychological needs can further predict the level of individual well-being(Zhang et al., 2017, Chen & Liu et al., 2020). The pursuit of intrinsic goals will produce an intrinsic tendency conducive to the satisfaction of psychological needs, thus showing better psychological adaptability, while the pursuit of extrinsic goals will cause an external tendency, which will focus on accumulating self-worth through external affirmation, thus reducing or hindering the satisfaction of psychological needs(Chen & Vansteenkiste et al., 2015). When psychological needs are satisfied, individuals will experience a strong sense of competence, be more satisfied with their interpersonal relationships, and ultimately promote mental health and subjective well-being(Ryan & Deci, 2002, Ryan & Deci, 2017). The research shows that basic psychological needs can also be used as a mediator to influence the relationship between exercise goal content and adolescents’ physical exercise behavior and subjective vitality(Xiang, 2014, Zhang & Xi, 2010). Therefore, satisfaction of psychological needs may be one of the mediating mechanisms of exercise goal content affecting subjective well-being。
In addition, exercise goal content can indirectly affect adolescents' subjective well-being through motivation(Zhao & Zhang et al., 2016). Organic Integration Theory (OIT)(Ryan & Deci, 2017) divides motivation into autonomous and controlled according to the degree of self-determination. Goal content has different effects on autonomous motivation and controlled motivation, the more prominent the self-development goal (intrinsic goal), the more positive the effect on autonomous motivation, and the more obvious the protective goal (extrinsic goal), the stronger the effect on controlled motivation(Ganotice & Downing et al., 2020). In addition, autonomous motivation and controlled motivation are interrelated with physical activity and well-being. Autonomous motivation can promote exercise behavior and well-being, while controlled motivation can inhibit exercise behavior and well-being(Fenton & Van Zanten et al., 2021). Therefore, exercise motivation mediates the relationship between exercise goal content and adolescent subjective well-being.
Exercise motivation and basic psychological needs may play a mediating role in the mechanism of exercise goal's influence on subjective well-being, but the order of their action still needs to be further explored. Motivation, needs and well-being are interrelated, forming a cycle or spiral, so it is difficult to distinguish the causal relationship between needs and motivation(Gunnell et al., 2014, Deci & Ryan, 2000, Milyavskaya & Koestner, 2011). The basic psychological needs theory holds that psychological needs are the most proximal variables affecting well-being, changes in psychological needs satisfaction can directly predict changes in well-being, and psychological needs satisfaction may no longer need an intermediary mechanism to promote well-being(Gunnell et al., 2014). However, some studies based on Vallerand's hierarchical model of internal-extrinsic motivation have confirmed that motivation can buffer the relationship between basic psychological needs and behavioral or emotional outcomes(Milyavskaya & Koestner, 2011, Ng & Ntoumanis et al., 2012). These findings contradict the above view of the basic theory of psychological needs, which suggests that "needs" point to something and "motivations" point to goals(Gopalan & Valarmathie et al., 2017). Motivation is a factor closer to behavioral goal than need. After an individual produces a behavioral goal, motivation causes and maintains an individual's specific goal to carry out activities, thus satisfying the individual's desire or desire for a certain goal. According to the motivation theory of cognitive theory, the adolescent's exercise goal, as a motivational variable, should first be related to exercise motivation, and then have an impact on the satisfaction of individual psychological needs. Therefore, As for the mechanism of exercise goal content affecting SWB, this study tends to predict psychological need satisfaction by motivation, among which, intrinsic exercise goal can positively predict individual autonomous exercise motivation, and exert positive influence on psychological need satisfaction through autonomous exercise motivation, thus improving adolescent SWB level; External exercise goals can positively predict controlled exercise motivation and negatively affect psychological needs satisfaction through controlled exercise motivation, thus reducing adolescents' subjective well-being.