• Wed. Jun 16th, 2021

Studies that will shape the future of non-filled systems

There is an uneasy silence around non-filled synthetic turf fields but, behind the scenes, FIFA, the industry and research institutions are studying the product extensively.

With the European Commission considering banning the sale of polymeric infill, many parties are betting on non-filled synthetic turf to secure the future of both the football fraternity and the synthetic turf industry. Non-filled systems for football have been around since 2003 and have been embraced by Switzerland and the Scandinavian countries. Most other European countries started to consider the system only around 2018. That same year, FIFA updated its testing criteria for football turf and concluded that previously approved systems were no longer compliant with the criteria stipulated in its latest Handbook of Requirements, hence it decided that systems that had been tested in accordance with the previous manual lost their product approval.

The trials in the Netherlands continued for the time being, until the Dutch FA (KNVB) concluded that more research was needed before it could finally give its approval to the product. At present, the fields can only be used for training and for youth games. “It is quite possible that the concept requires improvement but we are also looking at whether it is necessary to adapt the testing procedures. You can question the way in which we measure the quality of these artificial grass pitches,” says Patrick Balemans of the KNVB. In order to determine the exact problem, the KNVB has initiated a perception and experience study. In parallel, a process has been initiated to reconsider existing testing equipment. Once the perception and experience study has been concluded, insights gained should help fine-tune the equipment to ensure it can validate a field in accordance with the experience of the player. “Although hardly any matches are being played at present, our aim is to have both studies finished by 1 July this year,” says Balemans.

International studies

A great deal of research is also currently being carried out at international level. The FIFA Technical Advisory Group (FIFA TAG) made up of representatives of national football associations such as the German Football Association but also the KNVB, experts from the various synthetic turf manufacturers and representatives of the testing institutes accredited by the football governing body, has set up a special Non-filled Working Group. Colin Young of TenCate Grass is chairman of that working group. The discrepancy between the measured data and the opinion of players is also a key focus for the FIFA Working Group. “The feedback we receive from the players does not match the measured parameters. This is problematic, as the tests don’t replicate player experiences.” Something everybody is eager to avoid is a repeat of the experience seen in English football in the 1980s. The glorified hockey systems some of clubs installed at their match venues were, in fact, unsuitable for football. Young believes that, partly because of those experiences, football clubs at elite level are still reluctant to accept modern synthetic turf systems, despite the developments and improvements made over the past 30 years. The working group faces a difficult task. “FIFA wants to have standards that guarantee the safety and comfort of the player. However, at the same time, they do not want to be too strict because this would limit the opportunities for innovations for manufacturers. In view of the possible ban on the sale of polymeric infill, manufacturers must be given the space to come up with new solutions. Sharing research results with members of the FIFA TAG should help find a solution as soon as possible.” Although FIFA initiated the process only in 2020, Young believes that there is already sufficient knowledge available that the working group can draw on. “Collectively, we have several thousand hours of holistic research and many studies at our disposal already. Several of these studies have been carried out over a long period of time,” he states. His employer, TenCate Grass, started researching non-filled systems well before 2010. “That is why we are positive that we can get an agreement on the plans quickly.” Young aims to present a motivated proposal to the FIFA TAG which should already be good enough already for including it in the FIFA Quality Programme.

Player-field interaction

A common complaint about the non-filled fields in the Netherlands was that they offered less grip or were too slippery compared to systems with infill. Sheffield Hallam Universities Advanced Wellbeing Research Centre (AWRC) and TenCate Grass’s Centre for Turf Innovation have jointly launched a PhD research study to understand the effect of different synthetic turf pitches. “The discussion on microplastics is going to change the performance on synthetic turf drastically. What the effect of these changes will be is something that is not yet entirely clear. It is therefore important to know how the player experiences an artificial pitch before they are introduced,” is how Tom Wills motivates the research. “That interaction is a combination of biomechanics, consisting of forces and movements, and what the player experiences. We use high-speed cameras and motion caption equipment to properly capture the interaction between the player and the field. Think of the way in which the foot is being placed in the field.” Wills’s focus is on how the different components of the synthetic turf system work together. “My main focus is the performance of the synthetic turf system and the way in which changing a component such as the infill, shockpad or fibre, affects the player.”

Waiting for field tests

The literature study for the research has been completed. “One of the problems I’ve identified is that a lot the biomechanical research is often done in laboratories where space is limited. Generally, there is not enough possibility to measure the performance between different synthetic turf systems correctly. Test samples usually are only one meter wide.” Wills thinks he can change that by using the biomechanics lab at the AWRC and the space at the Centre for Turf Innovation at TenCate Grass. “This is the largest biomechanical laboratory in Europe. We can put three production samples, each four meters wide, next to each other. The players can perform the same movement at the same time. This is how we overcome the problem of large time differences between the different tests.” The limitations resulting from the COVID-19 pandemic are the reasons why the field research has not yet been initiated. Wills, however, is hopeful that this will change this spring.

In parallel with Wills’s study, the sliding friendliness of synthetic turf in general is currently also being studied. The research is funded by World Rugby and is being carried out by Cardiff University and testing institute Sports Labs. The first step in this study is to get a better understanding of what causes a sliding wound. Once this has been established, a test method can be developed that can simulate a player receiving such an injury. In the meantime, a prototype test instrument has been developed that is now used to collect data.

Other testing equipment

The possible limitations of current testing methods and testing equipment are being studied by David Cole of Loughborough University. The study took of in September 2020 and will last about 18 months. “Our literature research shows that the first 15 degrees under which a foot is put in grass, hybrid or synthetic turf are very different. The mechanical properties and the highest resistance and force that are now being measured do not adequately record the small details that are essential to a player,” Cole explains. “We plan to adapt the Advanced Artificial Athlete (AAA) based on literature information, biomechanical studies and the data we have collected here in our own laboratory during testing. The adjustments will be evaluated using player-perception studies to see to what extent they match with what the players actually do on the field. The information from the first two steps is taken into account when adjusting the AAA, the rotational resistance, as well as the test protocols, after which we can evaluate the extent to which they now give values that are in line with what the player does on the pitch.”

Just because it is quiet about non-filled fields doesn’t mean that the idea has been abandoned. At present, the various synthetic turf system developers are waiting for a little more clarity. As soon as the research studies start yielding results, development of non-filled systems will continue at full speed.


This article was commissioned by Fieldmanager Magazine from the Netherlands

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