The influence of playing surface on the loading response to soccer-specific activity

Context: The influence of playing surface on injury risk in soccer is contentious, and 6 contemporary technologies permit an in-vivo assessment of mechanical loading on the 7 player. Objective: To quantify the influence of playing surface on the PlayerLoad elicited 8 during soccer-specific activity. Design: Repeated measures, field-based. Setting: 9 Regulation soccer pitches. Participants: 15 amateur soccer players (22.1 ± 2.4 yrs), injury 10 free with ≥ 6 yrs competitive experience. Interventions: Each player completed 11 randomised order trials of a soccer-specific field test on natural turf, astroturf and third 12 generation artificial turf. GPS units were located at C7 and the mid-tibia of each leg to 13 measure triaxial acceleration (100Hz). Main Outcome Measures: Total accumulated 14 PlayerLoad in each movement plane was calculated for each trial. Ratings of perceived 15 exertion (RPE) and visual analogue scales (VAS) assessing lower-limb muscle soreness 16 were measured as markers of fatigue. Results: ANOVA revealed no significant main 17 effect for playing surface on total PlayerLoad (P = 0.55), distance covered (P = 0.75), or 18 post-exercise measures of RPE (P = 0.98) and VAS (P = 0.61). There was a significant 19 main effect for GPS location (P < 0.001), with lower total loading elicited at C7 than mid20 tibia (P < 0.001), but with no difference between limbs (P = 0.70). There was no unit 21 placement x surface interaction (P = 0.98). There was also a significant main effect for 22 GPS location on the relative planar contributions to loading (P < 0.001). Relative planar 23 contributions to loading in the AP:ML:V planes was 25:27:48 at C7 and 34:32:34 at mid24 tibia. Conclusions: PlayerLoad metrics suggest that playing surface does not influence 25 mechanical loading during soccer-specific activity (not including tackling). Clinical 2 26 reasoning should consider that PlayerLoad magnitude and axial contributions were 27 sensitive to unit placement, highlighting opportunities in the objective monitoring of load 28 during rehabilitation.