The influence of natural grass pitch hardness on soccer performance and game characteristics

<p> <b>Introduction</b>: Traditional natural grass pitches are the most prevalent surface at amateur-level soccer. Environmental considerations such as the climate, weather, grass coverage and seasonal variations all have an impact on the natural grass characteristics and affect performance of both player and surface. A key natural grass pitch variable that may influence the performance characteristics is the surface hardness. Therefore, the aim of the project was to examine the influence of natural grass surface hardness on amateur-level soccer performance and game characteristics via a mixed-method, multidisciplinary approach. </p><p><b><br></b></p><p><b>Methods</b>: Four separate studies were carried out, consisting of one performance analysis case study, two experimental studies and one focus group. In the first study, one academy-level (amateur) u-19 soccer player played in eleven competitive matches on soft and hard natural grass pitches. In the second study, ten academy-level (amateur) College soccer players completed a repeated sprint protocol of 40-m performed on two natural grass pitches of contrasting surface hardness. In the third study, performance, biomechanical and physiological responses were assessed during steady state running and an 84-minute soccer simulation protocol on soft vs. hard natural grass pitches. In studies one-to-three surface hardness was measured using a Clegg Impact Hammer and pitches were categorised into either hard or soft. In study four, four participants answered nine open-ended questions in a focus group covering four main areas including the technical, tactical, physical and psychological concepts of playing and coaching soccer on natural grass pitches with contrasting surface hardness. </p><p><b><br></b></p><p><b>Results: </b>In study one there were more turns on the soft vs. hard pitches (effect size; Cohen’s d) (i.e., sharp right (d = 1.4; P<0.05), sharp left (d = 0.2; P>0.05), smooth (d = 0.5; P>0.05), V-cut (d = 0.7; P>0.05), moderate intensity (d = 0.8; P>0.05), and high intensity (d = 0.1; P>0.05)), although there were slightly more linear turns on hard vs. soft pitches (d = 0.1; P>0.05). There was a trend for more movements on soft vs. hard pitches (i.e., high intensity shuffling (d = 1.7; P>0.05), running (d = 1.1; P>0.05), low (d = 1.1; P>0.05), and high intensity activities (d = 1.2; P>0.05)). In study two there was a trend for faster repeated sprints (d = 0.6; P>0.05) on the hard vs. soft pitch (mean ± sd; 6.00 ± 0.42 s vs. 6.22 ± 0.33 s, respectively). There was a trend for a greater fatigue in sprint performance (d = 0.8; P>0.05) on the hard pitch vs. soft pitch (mean ± sd; 7.12 ± 2.28 % vs. 5.20 ± 2.43 %, respectively). In study three mean sprint (d = 0.1; P>0.05) and cutting times (d = 0.1; P>0.05) were not different between the two surfaces during the soccer simulation protocol. Mean turn times (d = 1.4; P<0.05) were faster on the soft vs. hard pitch (mean ± sd; 2.39 ± 0.04 s vs. 2.44 ± 0.09 s) during the soccer simulation protocol. Contact times were shorter during steady state jogging (d = 1.1; P<0.05) on the hard pitch (mean ± sd; 0.277 ± 0.018 s) vs. soft pitch (mean ± sd; 0.294 ± 0.012 s) and shorter during sprinting movements (d = 1.0; P<0.05) on the hard pitch (mean ± sd; 0.148 ± 0.007 s) vs. soft pitch (mean ± sd; 0.155 ± 0.007 s) implying that playing surface influenced the mechanics of jogging and sprinting. In study four players and coaches showed inconsistent views on the impact of surface hardness on soccer performance but showed a preference towards playing soccer on hard pitches because of less physical demand and better technical execution (game-related events), tactical options, movements (i.e., linear and turning movements) and improved execution of movements. </p><p><b><br></b></p><p><b>Conclusion: </b>This project illustrates that changes in natural grass surface hardness affects some factors which are important to soccer performance. Players turn faster and more frequently on soft pitches. Contact times were shorter on hard pitches and there was a trend for faster sprints on the hard pitches during the repeated sprint and simulated soccer test. Physiological responses did not differ between surface which showed the players worked equally hard on both surfaces. Soccer players and coaches predominantly showed a preference towards playing soccer on hard pitches over soft pitches.</p>