REDA , Dr. Khaled Mohamed; HUSSEIN , Dr. Muthanna Abdul Amir Abdul; KHUWAIBIR , Dr. Khaled Habib; JAWAD, Dr. ALAA FLAYYIH. 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. Excellencia: International Multi-disciplinary Journal of Education (2994-9521), [S. l.], v. 3, n. 1, p. 55–70, 2025. DOI: 10.5281/. Disponível em: https://multijournals.org/index.php/excellencia-imje/article/view/2959. Acesso em: 9 nov. 2025.