The influence of natural grass surface hardness on path changes, locomotive movements and game events in soccer: A case study

Sporting performance and outcomes are affected by surface type and hardness. Natural grass surface characteristics can vary considerably at amateur level sport which can influence technical skills and locomotive movements. Surface hardness and human responses need to be objectively measured in order to fully understand movement responses and subsequent performance. In the present study, one academy u-19 soccer player played in eleven competitive matches. Surface hardness was measured using a Clegg Impact Hammer and pitches were categorised into either harder or softer groups (67.7 to 93.0 Gmax and 41.4 to 58.3 Gmax respectively). The frequency of high intensity shuffling was significantly greater on softer grass (11.2±2.1) when compared to harder grass (6.1±3.8) (p < 0.05). A large effect size was revealed with running, dribbling, low and high intensity activities as greater frequencies were evident on softer grass when compared to harder grass. There were no significant differences for any of the game events, but there was a large effect size for aerial challenges and headed clearances which were performed more often on softer surfaces than on harder surfaces. There was a greater frequency of moderate intensity, sharp path changes to the right and v-cut path change performed on softer surfaces than on harder surfaces and the effect sizes were large. To conclude, movement activity and game events performed were influenced by natural grass surface hardness. Future research should endeavour to explore differences in the physical work-rate in terms of the biomechanical and physiological demands.