title: The within-match patterns of locomotor efficiency during professional soccer match play: Implications for injury risk?
abstract: OBJECTIVE
  The principle aim of the current study was to examine within-match patterns of locomotor efficiency in professional soccer, determined as the ratio between tri-axial accelerometer data (PlayerLoad™) and locomotor activities. Between match variability and determinants of PlayerLoad™ during match play were also assessed.
  
  
  METHODS
  A single cohort, observational study.
  
  
  METHODS
  Tri-axial accelerometer data (PlayerLoad™) was recorded during 86 competitive soccer matches in 63 English championship players (574 match observations). Accelerometer data accumulated (PlayerLoad Vector Magnitude [PLVM]) from the individual-component planes of PlayerLoad™ (anterior-posterior PlayerLoad™ [PLAP], medial-lateral PlayerLoad™ [PLML] and vertical PlayerLoad™ [PLV]), together with locomotor activity (Total Distance Covered [TDC]) were determined in 15-min segments. Locomotor efficiency was calculated using the ratio of PLVM and TDC (PlayerLoad™ per metre). The proportion of variance explaining the within-match trends in PLVM, PLAP, APML, APv, and TDC was determined owing to matches, individual players, and positional role.
  
  
  RESULTS
  PLVM, PLAP, APML, APv and TDC reduced after the initial 15-min match period (p=0.001; η(2)=0.22-0.43, large effects). PL:TDC increased in the last 15min of each half (p=0.001; η(2)=0.25, large effect). The variance in PLVM during soccer match-play was explained by individual players (63.9%; p=0.001) and between-match variation (21.6%; p=0.001), but not positional role (14.1%; p=0.364).
  
  
  CONCLUSIONS
  Locomotor efficiency is lower during the latter stages of each half of competitive soccer match-play, a trend synonymous with observations of increased injury incidence and fatigue in these periods. Locomotor efficiency may be a valuable metric to identify fatigue and heightened injury risk during soccer training and match-play.
authors.affiliation: Department of Sport, Health and Exercise Science, The University of Hull, UK; Sport Medicine and Science Department, Hull City Tigers FC, UK. Electronic address: s.barrett@2006.hull.ac.uk.
authors.forename: Steve
authors.initials: S
authors.lastname: Barrett
authors.affiliation: Department of Sport and Physical Activity, Edge Hill University, UK.
authors.forename: Adrian
authors.initials: A
authors.lastname: Midgley
authors.affiliation: Medicine and Sport Science Department, Leicester City FC, UK.
authors.forename: Matt
authors.initials: M
authors.lastname: Reeves
authors.affiliation: Medicine and Sport Science Department, Leicester City FC, UK.
authors.forename: Tom
authors.initials: T
authors.lastname: Joel
authors.affiliation: Medicine and Sport Science Department, Reading FC, UK.
authors.forename: Ed
authors.initials: E
authors.lastname: Franklin
authors.affiliation: Medicine and Sport Science Department, Blackburn Rovers FC, UK.
authors.forename: Rob
authors.initials: R
authors.lastname: Heyworth
authors.affiliation: Department of Sport, Health and Exercise Science, The University of Hull, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Garrett
authors.affiliation: Western Sydney High Performance Sports Group, University of Western Sydney, Australia.
authors.forename: Ric
authors.initials: R
authors.lastname: Lovell
mesh_terms: D061725:Accelerometry; D000328:Adult; D000704:Analysis of Variance; D001265:Athletic Injuries / Q000517:prevention & control*; D054874:Athletic Performance / Q000502:physiology*; D015331:Cohort Studies; D005221:Fatigue / Q000503:physiopathology; D040362:Geographic Information Systems; D006801:Humans; D015994:Incidence; D008124:Locomotion / Q000502:physiology*; D008297:Male; D005082:Physical Exertion / Q000502:physiology*; D012307:Risk Factors; D012420:Running / Q000502:physiology*; D012916:Soccer / Q000293:injuries / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult
keywords: Accelerometry; Fatigue; Football; Injury risk