إ The research aimed to identify the effect of using hypoxic training on the development of muscular endurance (muscular endurance of the arms - muscular endurance of the abdomen - muscular endurance of the legs) and the level of performance of the compulsory motor sentence on the throat horse device for junior gymnastics under (14) years, and the researcher used the experimental approach on a sample of (10) junior gymnastics under (14) years, and research tools: Physical tests - Evaluation of the level of performance of the compulsory motor sentence on the throat horse device for junior gymnastics under (14) years - Training program using hypoxic exercises, Among the statistical methods used: arithmetic mean - standard deviation - median - torsion coefficient - simple correlation coefficient - test "T" - improvement rates. Among the most important results: 1- Hypoxic training has a positive effect statistically at the level of (0.05) on muscular endurance (muscular endurance of the arms - muscular endurance of the abdomen - muscular endurance of the legs) for junior gymnastics under (14) years. 2- The presence of improvement rates in the dimensional measurement of the tribal members of the basic research sample in muscular endurance, where the improvement rates ranged between (11.74% - 25.26%). 3- Hypoxic training has a positive effect statistically at the level of (0.05) on the level of performance of the compulsory motor sentence on the throat horse device for junior gymnastics under (14) years. 4- The existence of improvement rates in the dimensional measurement of the tribal members of the basic research sample in the level of performance of the compulsory motor sentence on the throat horse device, where the improvement rate was (16.18%).