The research aims to study the effect of 5-10-15 training on developing critical speed, some physical and physiological variables and the numerical level of the 1500 meter running race for juniors under 18 years old. The experimental method was used, and the research sample was chosen purposively from junior track and field athletes at Kafr Saqr Club during the (2021/2022) season. The research sample was selected purposively from the research population who had the best times in the 1500 meter running race, and their number was (10) juniors, and they were divided into two groups, one experimental and the other control, and the composition of each group was (5) juniors. The 5-10-15 training was applied to the experimental research sample during the special preparation period for (8) weeks, at a rate of 3 training units per week, and after the completion of the training program. Post-test measurements were conducted to identify the effect of 5-10-15 training on the development of critical speed, specific physical variables, and numerical level under investigation. The most important conclusions were that the 5-10-15 training contributed to the development of critical speed, some specific physical abilities, and the numerical level for the 1500-meter running race under investigation. The most important recommendations included relying on 5-10-15 training in developing critical speed, physical and physiological variables, and running performance for athletes of different age groups in track and field competitions. Using the 5-10-15 training method to develop specific athletic performance and physiological and biomechanical variables in track and field competitions. Combining 5-10-15 training with other training methods aimed at developing strength and muscle power and testing its effect on the numerical level of middle and long-distance running races.