The within - match patterns of locomotor efficiency during Professional Soccer match play : 1

30 Objectives: The principle aim of the current study was to examine within-match patterns of locomotor 31 efficiency in Professional Soccer, determined as the ratio between tri-axial accelerometer data 32 (PlayerLoad) and locomotor activities. Between match variability and determinants of PlayerLoad 33 during match play were also assessed. Design: A single cohort, observational study. Methods: Tri34 axial accelerometer data (PlayerLoad) was recorded during 86 competitive soccer matches in 63 35 English championship players (574 match observations). Accelerometer data accumulated 36 (PlayerLoad Vector Magnitude [PLVM]) from the individual-component planes of PlayerLoad 37 (anterior-posterior PlayerLoad [PLAP], medial-lateral PlayerLoad [PLML] and vertical 38 PlayerLoad [PLV]), together with locomotor activity (Total Distance Covered [TDC]) were 39 determined in 15-min segments. Locomotor efficiency was calculated using the ratio of PLVM and 40 TDC (PlayerLoad per metre). The proportion of variance explaining the within-match trends in 41 PLVM, PLAP, APML, APv, and TDC was determined owing to matches, individual players, and 42 positional role. Results: PLVM, PLAP, APML, APv and TDC reduced after the initial 15-min match 43 period (P=0.001; η=0.22-0.43, large effects). PL:TDC increased in the last 15 minutes of each half 44 (P=0.001; η= 0.25, large effect). The variance in PLVM during soccer match-play was explained by 45 individual players (63.9%; P=0.001) and between-match variation (21.6%; P=0.001), but not 46 positional role (14.1%; P= 0.364). Conclusions: Locomotor efficiency is lower during the latter 47 stages of each half of competitive soccer match-play, a trend synonymous with observations of 48 increased injury incidence and fatigue in these periods. Locomotor efficiency may be a valuable 49 metric to identify fatigue and heightened injury risk during soccer training and match-play. 50