The information available in sports medicine regarding the development of performance and maximum stress is presented for children and adolsecents, and the importance of age-appropriate sports for general health is also discussed. A description of the five main forms of stress on the motor system follows, i.e., coordination, flexibility, strength, speed, and endurance, and their effectos on the performance parameters boys and girls from childhood to adolescence. Data on cardiopulmonary-metabolic performance parameters are discussed for children and adolescents. These include functional and morphological data on the heart, circulation, respiration, metabolism, and skeletal musculature. Precocious young people are physically capable of a higher performance level and can tolerate more stress than their normal counterparts or those with delayed development. With regard to the five forms of stress mentioned above, health questions related to the ability to tolerate stress and age-related levels of training are dealt with. The negative effects on health are considered with regard to the development of amenorrhea and a decrease in the mineral content of the skeletal system as a result of extensive endurance training.