Systematic Bias between Running Speed and Metabolic Power Data in Elite Soccer Players : Influence of Drill Type

The aims of the present study were to: i) evaluate the agreement between estimates of highintensity activity during soccer small-sided games (SSGs) based on running speed alone and estimated metabolic power derived from a combination of running speed and acceleration; ii) evaluate whether any bias between the 2 approaches is dependent upon playing position or drill characteristics. 3 types of SSGs (5vs5, 7vs7 and 10vs10) were completed by 26 English Premier League outfield players. A total of 420 individual drill observations were collected over the playing season using portable global positioning system technology. High-intensity activity was estimated using the total distance covered at speeds > 14.4 km · h − 1 (TS) and the equivalent metabolic power threshold of > 20 W · kg − 1 (TP). We selected 0.2 as the minimally important standardised diff erence between methods. High-intensity demands were systematically higher (~100 %, p < 0.001) when expressed as TP vs. TS irrespective of playing position and SSG. The magnitude of this diff erence increased as the size of SSG decreased (p < 0.01) with a difference of ~200 % observed in the 5vs5 SSG. A greater diff erence between TP and TS was also evident in central defenders compared to other positions (p < 0.05) particularly during the 5vs5 SSG (~350 %). We conclude that the high-intensity demands of SSGs in elite soccer players are systematically underestimated by running speed alone particularly during “small” SSGs and especially for central defenders. Estimations of metabolic power provide a more valid estimation as to the true demands of SSGs.