title: Systematic bias between running speed and metabolic power data in elite soccer players: influence of drill type.
abstract: The aims of the present study were to: i) evaluate the agreement between estimates of high-intensity 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 in-season period 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 difference 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 difference increased as the size of SSG decreased (p<0.01) with a difference of ~200% observed in the 5vs5 SSG. A greater difference 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.
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: P
authors.initials: P
authors.lastname: Gaudino
authors.affiliation: Department of Biomedical Sciences for Health, Università degli Studi di Milano, Italy.
authors.forename: F M
authors.initials: FM
authors.lastname: Iaia
authors.affiliation: Department of Biomedical Sciences for Health, Università degli Studi di Milano, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Alberti
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: R D
authors.initials: RD
authors.lastname: Hawkins
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: A J
authors.initials: AJ
authors.lastname: Strudwick
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: W
authors.initials: W
authors.lastname: Gregson
mesh_terms: D000054:Acceleration; D000328:Adult; D004734:Energy Metabolism; D040362:Geographic Information Systems; D006801:Humans; D010806:Physical Education and Training / Q000379:methods*; D010807:Physical Endurance / Q000502:physiology*; D012420:Running / Q000502:physiology*; D012916:Soccer / Q000502:physiology*; D013996:Time and Motion Studies; D055815:Young Adult