The research aimed to study the effect of mixing between (plats-weight) exercises on the balance of the dynamic force between the muscles of the two sides of the body and the muscles of the one party (extension-Flexion) and the effect of this on the improvement of the kinematic performance and the digital level of butterfly swimmers, and the researcher used the experimental approach A sample of 15 swimmers.Research tools include: Anthropometric- physical, performance variable, digital measurements, The researcher used the statistical program SPSS in order to obtain:Arithmetic Mean,Standard derivation, ,T-test and Sekwness, Correlation coefficient,Rat of Improvement. Results:The improvement in the percentage differences of the muscle balance of the muscles of the two sides of the body and the muscles (extension-Flexion) per side contributes to the improvement of the kinematic performance and the digital level of the swimmers.The researcher recommends: Attention to achieving muscle balance between the muscles on both sides of the body and on the one side of swimmers. Keywors: oxygen saturation, monocarboxylate transporters