In this research, under the title of “Comparative study of some physiological abilities according to these lines of play (defense - center and attack) for football players under the age of 17”, we tried hard to detect the differences of some physiological capacities. Consequently, we suggested two hypotheses which are: 1) there are many differences in some physiological capacities according to the lines of playing, and 2) the competition has effects on some physiological capacities of football players according to the lines of playing. Therefore, to confirm the validity of the hypothesis or deny it, we as researchers, conducted a descriptive method on a sample consisted of 15 players from the youth team of Tiaret where the sample was chosen intentionally and in the light of the theoretical and the field study, in which we identified the research tools, which were the functional tests, and also through the scientific foundations (validity, constancy, and objectivity). The results of the study revealed many differences in some physiological abilities by playing lines (defense - center - attack) and resulted in that competition affects positively on some physical capacities according to these lines (defense, center and attack). The most important recommendations were to generalize the results of this study to the rest of the other states. This is in order to increase the confirmation and validity of the results obtained. Also, in view of the objectives of the study and its results, appears a need for further studies that deal with physical capacities that reflect an important factor in the planning of sound training programs and implemented during a competitive phase.