There is a need to differentiate between (triathlon) training for adults and (triathlon) training for children. They have different processes of adaptation to the different sports qualities: speed, strength, endurance, coordination and agility. For children it depends on: physiological age, mental age, hormonal maturation and sex. Also, physical and mental developments are not always in sync. It is the responsibility of the sports educator to take into account these differences for the correct progression of the child's training.