Comparison of the physical fitness of Iran premier league soccer players in youth and adult age categories

High-intensity running performance capacity, maximal sprinting speed and change of direction ability are among the most important physical fitness factors to succeed in elite soccer. It has also been suggested that total training load is a critical determinant for the level of soccer players’ fitness improvement. Our hypothesis was that adult players have a higher level of physical fitness than their younger counterparts and tolerate higher training loads. Therefore, the aim of this study was to compare some of physical fitness factors and weekly training loads of Iran premier leagues in youth and adult age categories during the in-season phase. 22 players of Sepahan F.C from adult (n: 12; age: 28.3) and youth (n: 10; age: 18.0 yrs) categories, participated in this study. During the half season rest period, 30-15 Intermittent Fitness Test (30-15IFT), linear 10-meter and 30-meter sprint and 5O5 tests were used to measure high-intensity running performance, spring speed and change of direction ability, respectively. In-season phase internal training loads were also collected using total amount of session time (min) and rate of perceived exertion (sRPE) on a daily basis. Statistical analyses were implemented using the progressive statistics in sport science with special reference to magnitude-based inference. Acceleration, maximal sprint and change of direction ability were all superior in adult players with moderate (effect size: 0.96), moderate (0.81) and small (0.24) effects, respectively. High-intensity running performance and sRPE were higher in youth players with the small (0.39) and moderate (1.12) magnitudes, respectively. In daily analyses, the most different factor observed was the training load on the second day after the match (D+2) with the magnitude of 2.47 (very large) in youth age category. High-intensity running performance and sRPE, opposite to our hypothesis, were higher in youth players. It seems that the higher high-intensity running performance capacity observed in youth age category was due to their moderately larger training load. The superior speed-dependent factors (acceleration, maximal sprint and change of direction ability) observed in adult players, are probably related to the higher rate of selection of faster players existed in the talent identification strategies implemented in professional clubs Therefore, increasing the training load in Iran premier league players in adult age category seems to be essential to promote their weak high-intensity running performance capacity.