The research aims to identify the effectiveness of using cross-training on mental toughness in (self-confidence - negative energy - attention control - visual perception control - motivation level - positive energy - Attitude Control), and the development of special physical capabilities (explosive strength - agility - balance - flexibility) and the degree of skillful performance of aerobic gymnasts. The researcher used the experimental method using the design of one experimental group (pre-measurement - post-measurement).The research sample was deliberately chosen from the youth of gymnastics under 14 years old at the Suez Canal Authority Club in Port Fouad, and the basic experimental sample included 4 players, and the two researchers also used 4 players from outside the basic research sample but from the same research community to conduct the exploratory study and the scientific treatment of the tests used. The most important results were that The proposed cross-training program has a positive effect on improving the determinants of mental toughness, the effect on developing the special physical abilities, and had a positive effect on improving the degree of skill performance of aerobic gymnasts under the age of 14.