There is consensus about the psychological and social benefits that sport can produce in childhood and adolescence (Holt, 2008; Swann et al., 2018; Tomporowski, Lambourne, & Okumura, 2011). For this reason, there are many programmes aimed at promoting the practice of sport among the youngest and encouraging their adherence (Duda et al., 2013). However, some critical positions have warned about the need to develop sports contexts adapted to these ages in order to avoid situations that generate effects contrary to those desired. Environments with disproportionate physical demands or high pressure for results could harm the physical and psychological health of athletes (DiFiori et al., 2018; Markati, Psychountaki, Kingston, Karteroliotis, & Apostolidis, 2018). The relationship between sport and the development of young people can be positive or negative, which requires the proper management of programmes and the education of the social agents surrounding the athlete. The role of coaches and parents in the athlete's training processes is very important, as is the establishment of satisfactory relationships between the athletes themselves (Álvarez, Balaguer, Castillo, & Duda, 2012; Holt, & Neely, 2011). Organizations must structure and plan the work carefully, establishing objectives and strategies to achieve a balance between competitive aspirations and potential personal and social development (Siedentop, Hastie, & van der Mars, 2004).

A classic theme in Sport Psychology and physical activity is the one related to the benefits of practicing sport for children and adolescents. It is well known that sport and physical activity constitute contexts for the development of cognitive, psychological and social benefits. Likewise, through sport you can develop strengths of character, values and aspects related to the moral development of children and adolescents, of great importance for the life of the people. It is assumed that sport can generate a context in which children and adolescents can learn life skills and various positive attributes that facilitate development, both inside and outside of sports environments. However, participation in sport does not guarantee the development of positive characteristics in children and adolescents. Evidence indicates that adult leadership is the key factor in maximizing positive effects. Therefore, this chapter will address, first, some of the cognitive, psychological and social benefits that can be gained through the practice of sport, as well as some risks that may also arise from it. Secondly, different intervention programs in grassroots sport for young sportsmen and sportswomen, coaches and parents will be addressed. Coaches and parents are key socializing figures that influences on the quality of experience in sport. Their influence in the transmission of values and in moral development, their impact in emotional and affective responses, in motivation and involvement but also in representing sources of stress, burnout or drop out has been shown all around the world with different children and adolescents. All interventions seek to promote values, educating through sport and prioritizing the experience of sport as a socializing experience and psychosocially healthy action. The relationship between sport and the development of young people can be positive or negative, which requires the proper management of programmes and the education of the social agents surrounding the athlete. The role of coaches and parents in the athlete's training processes is very important, as is the establishment of satisfactory relationships between the athletes themselves (Álvarez, Balaguer, Castillo, & Duda, 2012; Holt, & Neely, 2011). Organizations must structure and plan the work carefully, establishing objectives and strategies to achieve a balance between competitive aspirations and potential personal and social development (Siedentop, Hastie, & van der Mars, 2004).