From the player perspective, the primary aims for any playing surface is to help maximise their performance and comfort, whilst minimising risk of injury. User safety can be investigated through:
- Epidemiological studies
- Experimental biomechanics
- Computer simulation modelling
- Player Feedback
These areas have significant overlap with the ‘play performance’ of a sports field.
Each of these research methods has limitations and current knowledge directly relating the effect of surface state on player biomechanics and injury risk remains limited.
The subject of injury risk is broad and very complex, particularly if the full range of risk factors is considered and a full review of the details of the many epidemiological studies in team sports – even with the specific focus here on sport surfaces. There have been many major studies on injury incidence, some in reports by government-related bodies such as the European Union (EU), and some on behalf of the sport governing bodies.
For example, in a 2007 EU report soccer was stated as responsible for most injuries comprising 36 per cent of the 2 500 000 sport-related injuries reported, and hockey sixth comprising 5 per cent. A study in Australia reported that soccer was responsible for 8 per cent of the total injuries recorded, and rugby and hockey were found to be responsible for 8 and 3 per cent, respectively.
An added complexity for reviewing past injury studies is that the classification and categorization of injuries and injury types are not comparable between studies reported from around the world. In response to this, a consensus statement was developed in 2006 on injury definitions and data collection procedures for studies in soccer, and subsequently for rugby union in 2007. The definition of injury therein includes any physical complaint sustained by a player that results from a match or training, and the analysis and reporting method promotes the expression of injuries per 1000 hours of exposure (typically) – leading to a much better determination of risk and risk management strategies. This specific development in harmonizing data collection has been pivotal and underpinned the recent work of FIFA and the IRB in their research into injury risk of artificial turf in comparison to natural turf. Two studies concluded that injuries on natural and artificial turf, for both genders, was more than seven times higher in a match situation than during a training situation based on the incidence per 1000 playing hours. During the FIFA 2002 and 2006 World Cups the injury incidence in the matches was recorded as extremely high at 81 and 69 per 1000 playing hours, and was compared to a maximum of 28 per 1000 hours in other comparable studies. The increase was attributed to the high value and high intensity of these tournaments, and also relatively short rest periods between matches.
However, against the context of these findings of a relatively high risk of injury at the elite level of professional soccer the question of what changes in injury statistics or patterns is less clear for the surface as a factor, or as a consequence of change in surface from natural to artificial, or from training on artificial and playing on natural, or from varying properties across pitches. There has been concern of a perceived higher risk of injuries on artificial turf in comparison to natural turf for many years, and to some extent this still exists in contemporary media coverage. However, some relatively recent robust injury studies have concluded that there is no difference in risk of injury between natural and artificial surfaces in soccer, however some studies have concluded a difference in the types the injuries.
However, there remains a lack of detail in nearly all injury studies regarding the properties of the surfaces utilized and very little research to date into natural turf behaviour and injury risk. In a study on the risk of anterior cruciate ligament (ACL) injuries in Australian rules football (AFL), they showed differences in injury risk for different species of natural grass (the species is usually chosen to suit the specific growing related climate of the region). Similarly, it is suggested here, that might not difference in pile length and tufting density combined with the type and amount of infill that is used across the range of artificial turf systems be considered to have similar possibilities for affecting the risk of injury to users on artificial turf surfaces?
Previous player injury studies have not provided real detail on the surface systems encountered in the studies, or their state at that time, made more complex by the constant evolution of surface technologies.
High surface temperatures are often recorded on or close to the surface of an artificial turf pitch (ATP). Many literature sources from different countries have reported surface temperatures on artificial pitches rising to 90-95°C on hot days, which has raised numerous concerns about health risks for adult and child users.
The SSRG efforts have primarily been focussed around surface traction, surface hardness, abrasion to skin, and heat.
The SSRG research framework divides the player–surface interaction into two broad aims:
- To understand the effect of the playing surface state on player biomechanics – recent research work has manipulated surface properties and trialled novel measurement methods to synchronously capture biomechanics and the surface response.
- To better understand the link between player biomechanics and injury risk. To achieve this goal the group works with specialist epidemiological researchers at other institutions such worldwide.
To support these goals there is a need for improved mechanical test methods that better simulate user movement and loading on the surfaces. However, there remains a paucity of information on the relevant boundary conditions for advancing these test methods.
The SSRG has also investigated the thermal behaviour of a fully instrumented (3G) ATP used for soccer, and from several similar ATPs and a natural turf field at Loughborough University. The data showed the ATP was warming up and cooling down very quickly, up to 2.5-3.0°C per minute. Solar radiation is the main factor driving the surface temperature fluctuations. A numerical model was developed to predict the surface temperatures and showed good approximation to the observed data. The model was used to show peak surface temperatures could be significantly reduced by increasing the albedo of the surface (Gustin et al., 2018).
- ‘Futsal – Player feedback and play performance specification’, International Football Federation (FIFA), 2013-2014, P Osei.
- ‘Elite player assessment of playing surfaces for football’, International Football Federation (FIFA), 2012-2014, P Osei.
- ‘ShoeSMART – Monitoring Gait’, 2012 Olympics related Feasibility Study, EPSRC/UK Sport, J Ronkainen/C Young.
- ‘Hockey Pitch Performance, World Class Water Programme’, England Hockey/ Sport England.
- ‘Skin Friendliness of Artificial Turf’, LU/ISR joint PhD, S Tay Peng, 2016.
- ‘Reducing Surface Heating Effects of Artificial Turf’, MRes, M Gustin, 2016.
- ‘Modelling Heat Storage Extraction in Artificial Pitches’, MRes, S Watson, 2015.
- ‘Play Performance of Water-based Hockey Pitches’, C Young, 2006
Dr P Fleming was an invited visiting Research Fellow to Federation University (formerly Ballarat University), Melbourne Australia, 2015, 2011 and 2009, and an invited international member of ‘Injury Prevention and Safety Promotion’ consortium (Panel B-better understanding of player/surface interactions and their role in injury causation), Australia, 2009-2012.
Selected recent publications
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