Quantifying change of direction load using positional data from small-sided games in soccer

Rapid changes in velocity and direction place high mechanical loads on players, but are ignored in commonly used load indicators. Purpose : Quantifying change of direction (COD) load through positional data from small-sided games (SSG) and assess its criterion and construct validity. Methods:Elite male youth soccer players (n = 25, 16.8 +/- 1.3 years) played three SSG (5v5, 5x4 min) with different field dimensions (small [40x30 m], medium [55x38 m], large [70x45 m]). Positional data of the players was obtained with a Local Position Measurement system. COD load (AU) was quantified based on the combination of velocity and change in heading direction. Additionally, total distance covered, running distance, acceleration count, deceleration count, and Rating of Perceived Exertion were measured. Criterion validity was assessed by correlating COD load and the load indicators. Construct validity was determined by testing the differences between the SSG field dimensions. Results:Strong correlations were determined between COD load and total distance covered (r = 0.74, p < .01) and running distance (r = 0.84, p < .01). Middle and large field size resulted in highest COD load (p < .05). Conclusion:These results suggest that the COD load measure shows sufficient criterion and construct validity.