Overview
The ‘Play Performance’ of a sports pitch is a term widely used in the industry to describe whether the pitch meets specific criteria in relation to the player and/or ball. The term ‘quality’ is also often used to describe a pitch and this may include aspects, for artificial turf, of the pitch components and how well it meets other criteria for durability. For natural turf pitch quality would usually also describe, for example, aspects of the plant health, grass cover and so on.
It is interesting to observe that although specific ‘play performance’ criteria have existed for artificial turf systems since the early 2000’s such as those specified by the IGB’s FIFA, FIH and World Rugby, there is comparatively little regulation of natural turf or the more recent introduction of ‘hybrid’ turf systems. In general, the official IGB mechanical test methods used to describe the play performance of a sports field can be separated into ‘Player Surface related tests and ‘Ball-Surface’ related tests.
Player-Surface performance related mechanical tests for artificial turf, in brief, comprise measurements of ‘hardness’ or ‘shock absorbency’, traction (or grip), and ‘skin abrasion’ (laboratory only).
Ball-Surface performance related tests for artificial turf, in brief, comprise measurements of vertical ball rebound, and ball roll distance. Other related tests exist for measuring surface infill ‘splash’ (aesthetics), and loss of velocity for angled ball impacts (laboratory only).
In addition, field must also comply with criteria for acceptable surface evenness, and the infill depths and fee pile height should be reported.
For further information on surface testing see the latest IGB information available on their websites and chapter 3 of Dixon et al., 2015 (see below).
Group Activity
The current suite of performance related tests for sport surface systems are, in general, simplistic and limited in their ability to replicate real human loading and in-game behaviour. However, they are in general used to classify surface systems and corroborate acceptable levels of play performance.
Three key questions are identified and form much of the SSRG research in regard play performance:
- What properties of the surface are the current mechanical tests measuring and what factors influence the results?
- How does subject movement and loading on a surface compare to the boundary conditions controlling the mechanical test loading regimes?
- How can a surface be classified and reported in detail, and its state fully described, such that full comparison can be made between laboratory and field data sets across research and industry studies?
- How can player feedback be used to develop our understanding of play-performance?
Taking rotational traction as an example, the mechanical test involves measuring peak traction resistance of a 6-studded smooth plate under constant load of 450N (contact stress ~40 kPa) to a 90° rotation at 12 rpm. Peak traction only is reported, and observed to occur at ~40° rotation and required to fall within specific acceptability limits, typically 25–50 Nm. SSRG research has shown that peak traction resistance is very sensitive to the normal load (stress) applied, infill density and stud geometry/configuration (Severn, 2010). Furthermore, from test subjects in our laboratory performing a 180° turn boot rotation measured during ground contact was only ~12°. Peak utilised traction occurred during initial weight acceptance where vertical loading reached ~2 bodyweights and peak contact stresses were estimated at up to 230 kPa. These player related data suggest the simple mechanical device may not be measuring what is most important to the surface user.
In addition, elastomeric infills and shockpads used in artificial turf behave non-linearly under compressive loading with variable hysteresis and energy return responses under different loading rates. Consequently, a player applying higher compressive stresses and lower loading rates compared to the mechanical tests would generate a very different material/system response, and may generate much higher traction resistance, and at smaller material strains.
SSRG research continues to investigate and model the complex mechanical response of the components and surface systems (Anderson 2007, El Kati, 2013; Wang, 2013, Mehravar, 2016; Cole, 2018).
Research Projects
- ‘Novel Assessment and Characterisation of Sports Surfaces’, EPSRC/Labosport UK Ltd., Engineering Doctorate, Frazer Anderson, 2014-2018.
- ‘Numerical Model Development for Describing Artificial Turf Systems in Compression’, ISR/LU, M Mehravar, 2015-2016.
- ‘Futsal – Player feedback and play performance specification’, International Football Federation (FIFA), 2013-2014.
- ‘Elite player assessment of playing surfaces for football’,International Football Federation (FIFA), 2012-2014.
PhD Projects
- ‘Predicting Behaviour of Artificial Turf Systems using Numerical Modelling’, D Cole, 2019 (due).
- ‘Player-Surface Interaction for Rugby – measuring boot-surface interaction’, A M Ferrandino, 2018 (submitted).
- ‘Traction Behaviour of Artificial Turf’, C Webb, 2017.
- ‘Advanced Measurement For Sports Surface System Behaviour Under Mechanical And Player Loading’, X Wang, 2013.
- ‘Effect Of Mechanical Behaviour Of Artificial Turf On Player-Surface Interaction In Soccer’, R El-Kati, 2013.
- ‘Science of Synthetic Turf Surfaces: Player-Surface Interactions’, K Severn, 2010.
- ‘Elastomeric Shockpads for Outdoor Synthetic Sports Pitches’, L J Anderson, 2007.
- ‘Play Performance of Water-based Hockey Pitches’, C Young, 2006.
Enterprise Work
- Re-Design of a Sprung Floor – Birmingham Royal Ballet, UK.
- Guide on Artificial Turf – Sport & Recreation, Victoria, Australia.
- Cyclic Behaviour of Performance infill.
- Benchmarking ball-surface resilience on a range of performance infills.
Selected recent publications
Click here to view recent publications in this area.