Yousif Alnjola, O. and عمر 2023. A Comparative Study of the Performance Efficiency and Morphology of the Heart Among Long-Distance Runners. Al-Rafidain Journal For Sport Sciences (RJSS). 26, 81 (Jan. 2023), 491–500. DOI:https://doi.org/10.33899/rjss.2023.141888.1198.