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Players within the same age group may present different physical and physiological profiles. This study classified young soccer players according to their physical and physiological profiles obtained during the training sessions and compared classification by age and playing position criteria. 151 male elite Portuguese soccer players (under 15, under 17, and under 19 years old) participated. Time-motion and body acceleration and deceleration data were collected using GPS technology with heart rate monitored continuously across the selected training sessions. The data were grouped using two-step cluster analysis to classify athletes. A repeated-measures factorial ANOVA was performed to identify differences in the variables. Three clusters comprised 15.2%, 37.1%, and 47.7% of the total sample, respectively. Players of the same ages and playing experience had different performance profiles. Grouping players with similar physiological profiles during training sessions may allow coaches to balance oppositions and reduce the variability of the physiological outcomes. [ABSTRACT FROM AUTHOR] more...

The aim of this study was to identify differences in time–motion, modified training impulse, body load and movement behaviour between defenders, midfielders and forwards, during an 11-a-side simulated football game. Twenty elite youth male footballers from the same squad participated in this study (age: 18.1 ± 0.7 years old, body mass: 70.5 ± 4.3 kg, height: 1.8 ± 0.3 m and playing experience: 9.4 ± 1.3 years). All data were collected using GPS units (SPI-Pro, GPSports, Canberra, Australia). The movement behaviour was measured with kinematic data, used to calculate position-specific centroids (defenders, midfielders and forwards), and processed with non-linear statistical procedures (approximate entropy normalised and relative phase). There were significant effects and interactions in all variables across the players’ positions. The results showed that displacements of all players (defenders, midfielders and forwards) were nearer and more coordinated with their own position-specific centroids than with the other centroids. However, this coupling effect was stronger in midfield players and weaker in forwards. All players’ dynamical positioning showed more irregularity when related to the forwards’ centroid, as a consequence of their need to be less predictable when playing. The time–motion and physiological variables showed lower activity in forward players. Adding together, the results may contribute to a better understanding of players’ specific performances and football complexity. [ABSTRACT FROM AUTHOR] more...