A comparison of the physical load in match play and small-sided games in trained football players.

The internal and external demands of football have been the subject of increasing attention over the past 30 years. Global positioning systems (GPS) have become widely used by sports teams to quantify training and non-competitive match demands. Although GPS technology has been used in football for some time, its sensitivity in determining training and match demands has been debated. The recent integration of accelerometers and GPS may therefore provide a more detailed analysis through quantifying all actions as a total mechanical stress. Therefore, the aim of this investigation was to compare the internal and external demands of youth football players in four playing positions during small-sided games (SSGs) played with different player numbers in comparison to 11-a-side match play (MP). Forty trained sub elite youth football players classified into four positional roles; central defender (CD), wide defender (WD), central midfielder (CM) and forward (FW); participated in the study (Mean ± SD age 17.00 ± 0.60 yrs, stature 179.88 ± 6.15 cm, mass 73.93 ± 5.85 kg). Players were analysed during three different conditioned small-sided games (2 vs. 2, 3 vs. 3, and 4 vs. 4) in which two ball touches were allowed per possession. In addition, six friendly matches were also completed. Internal demands were measured via heart rate (HR), whereas external demands were measured by tri-axial accelerometry. Variables recorded were total distance covered per min, distance covered in different speed zones per min (0-6.0, 6.1-8.0, 8.1-12.0, 12.1-15.0, 15.1-18.0, and >18.1 km·h-1), distance covered in different acceleration and deceleration zones per min (0 to ± 1, ± 1 to 2, ± 2 to 3, ± >3 m·s-2), repeated high-intensity efforts, work:rest ratio, tri-axial accumulated player load per min and the relative contribution from the X, Y and Z vectors per min. When conditions were compared, significant main effects were found for accumulated player load per min (F = 21.91; p 18.1 km·h-1 (F = 96.18; p<0.001, η2 = 0.73) in which MP elicited significantly greater values than SSGs for each variable. When positional role were compared, significant main effects were found for total distance covered per min (F = 8.80; p 18.1 km·h-1 (F = 6.66; p = 0.001, η2 = 0.36) in which FW reported significantly greater values than the other positional roles. A significant interaction was found for distance covered at >18.1 km·h-1 (F = 4.31; p = 0.002, η2 = 0.26) in which FW reported significantly greater values than CD (8.74 ± 4.41 vs. 4.96 ± 1.82 m.min-1, respectively, p = 0.017) and CM (8.74 ± 4.41 vs. 3.89 ± 1.43 m.min-1, respectively, p = 0.001) during MP. Based on the accelerometry data in the present study, it is likely that the physical demands of football and more specifically SSGs have been underestimated when determined using more traditional time-motion analysis methods and GPS technology. The findings of the present study demonstrate that the PL and acceleration / deceleration patterns observed during SSGs are greater than those observed in friendly MP. Therefore, the SSGs employed may offer a ‘density’ type-training stimulus through imposing relative demands on acceleration and deceleration in excess of those experienced during MP.