Reda , D. K. M.; Hussein , D. M. A. A. A.; Khuwaibir , D. K. H.; JAWAD, D. A. F. The Effect of Circuit Training According To the Variation of Speed and Time in Improving the Speed Strength, Specific Endurance and Achievement of 400 M Freestyle Runners Under 20 Years. EIMJE 2025, 3 (1), 55-70. https://doi.org/10.5281/.