Hybrid football pitches: why the grass is always greener
Today’s top-level football pitches look pristine and play even better. The secret is hybrid grass: part real, part synthetic.
Today’s top-level football pitches look pristine and play even better. Even when it rained so much that this year’s Manchester City Champions League clash with Borussia Monchengladbach had to be cancelled, the stadium’s drainage facilities worked well enough to get the pitch playable for the following evening. Back in the 1960s and 70s, the winter rains turned English football pitches into mudbaths. The country’s best players would slide around, covered in mud and water, taking divot after divot out of the pitch. When it didn’t rain, the rain and play damage to the pitch was so great that the only green on the field would often be the goalkeeper’s shirt.
Back then, one of the worst mud heaps was Derby County’s Baseball Ground, but not because it rained more in the North Midlands than anywhere else. It’s said that Derby’s maverick manager Brian Clough sometimes instructed his ground staff to water the pitch, apparently believing a wet pitch suited his team’s style of play. He also thought the wetness would be an advantage against European teams, who Clough believed had superior technical ability, but didn’t fancy it when things got a bit rough.
Derby left the Baseball Ground in 1997 to play at nearby Pride Park. It’s now called the Ipro Stadium, after the manufacturer of isotonic sports drinks got the naming rights in 2013.
This season, the club has had a new high-tech playing surface installed on the main pitch and four training grounds. Whereas the previous one sometimes looked like it was 97 per cent mud and 3 per cent grass, this new one actually is 97 per cent grass and 3 per cent artificial fibres.
Phil Blackwell, project director with SIS Pitches UK, who installed the artificial fibres into the newly laid turf, says the company uses a giant laser-guided sewing machine on tracks to weave the polyethylene yarn into the ground.
Blackwell, who used to be Ipswich Town’s head groundskeeper, explains that the machine moves slowly across the pitch, implanting the yarn in rows 18cm deep into the sub-surface, with 2cm of the fibre poking out of the ground. At Derby, the fibres were placed at 2cm intervals, but the machine’s settings can be adjusted to provide wider gaps between yarns.
Three per cent artificial fibres might not seem much, but Blackwell says these fibres make all the difference. “With a 100 per cent natural pitch, you’ll see changes due to weather,” he explains. “Some pitches will change quite considerably throughout the year. Hybrid pitches maintain consistency and stability.”
Blackwell adds that “these fibres hold the root zone together. The natural grass grows around the fibres, anchoring it. When a player goes into the ground with their boots, the fibres stop the root zone from becoming displaced and there’s less chance of a player taking a divot out of the ground. The pitch recovers faster after a game as there’s less damage.”
Hybrid turf pitches are used worldwide by top-level football teams. All current Premier League sides have them, most designed by Desso Sports Systems. Hybrid pitches are also widely used in rugby, American football and baseball.
SIS Pitches has installed its hybrid surfaces at the Ta’Qali National Stadium in Malta, the Vodafone Arena in Turkey - home of Besiktas, Georgios Karaiskakis Stadium in Greece, where Olympiakos play and the Sammy Ofer Stadium in Israel. It has also installed hybrid training pitches for Chelsea, Hull City and at St George’s Park, the Football Association’s National Football Centre.
The SIS and Desso systems are similar, except that Desso uses polypropylene fibre, which is very strong, stiff and hard, whereas SIS uses a polyethylene fibre which it says is softer and therefore more comfortable for the players.
Over the years, some players and managers have accused hybrid pitches of being too hard and thus contributing to player injuries. Former Spurs and West Ham boss Harry Redknapp, recently retired England manager Roy Hodgson and French legend Thierry Henry, are three high-profile critics.
Harder surfaces, the argument goes, can lead to impact injuries in the legs and lower back. With less give in the surface, boots can get stuck in the turf, causing over-rotation in the lower limb, or a twisted ankle, if you’re speaking English.
“[On harder pitches] players can reach peak velocities quicker and they don’t get dead legs like they used to on the old soggy pitches,” says Mike Davison, managing director of Isokinetic Medical Group, London, part of the FIFA Medical Centres of Excellence Network. “The pitches deliver back more reactive energy to the players, but players will feel the shock going through their bodies, in their joints, bones and tendons.”
In 2015, Bournemouth striker Glenn Murray blamed the newly installed hybrid pitch for cruciate ligament injuries picked up by three Bournemouth players in the first four weeks of the season. The club later issued a public statement saying it had investigated the matter and found no connection.
Davison adds that so far, there is no clear scientific evidence that either refutes or supports the suggestion that hybrid pitches contribute to injuries. In 2014, FIFA and UEFA, the world and European governing bodies, released a study that claimed football (hybrid) turf presented no more or less risk of injuries than natural turf. “There was a slight increase in ankle injuries on football turf, but fewer muscle injuries,” says Dr Jan Ekstund, vice-chairman of the UEFA Medical Committee. The FIFA/UEFA study didn’t look at back pain and general soreness or long-term injuries, though.
Blackwell won’t be drawn on the issue, only to say that softer fibres (as used in SIS pitches) might be better for players during sliding tackles.
All modern football pitches are designed to cope with a lot of water in a short period of time. They have sand or gravel root zones and drain at high rates. In certain parts of the world however, pitches also have to contend with temperatures that drop well below zero.
SIS engineers are installing SISGrass into Moscow’s Luzhniki Stadium (pictured above and below, during construction), the host stadium for the 2018 World Cup Final. Spartak Moscow’s brand new Otkritaya Arena, the 43,000-seater stadium, is expected to stage World Cup group stage matches and a semi-final.
In January, the average temperature in Moscow is -7.5°C. although temperatures have been known to drop to -42°C. The Russian Premier League has a winter break from December until mid-March to avoid the worst of it, but the grass on the pitches still has to cope with the snow, ice and frost.
Under-soil heating is a mandatory part of the modern football ground, but some clubs also use sub-air systems to blow warm air into the soil through holes in pipes that run under the pitch.
SIS Pitches has installed its own system, SISAir, into the Moscow pitches. Blackwell describes it as a drainage system in a pitch that’s connected to a big fan.
“The fan can either blow air through the drainage system and up through the pitch profile or it can be reversed, drawing air down through the pitch profile, removing moisture as it does so,” he says. “With a system like this, you can maintain the optimum air and moisture conditions within the soil profile.”
Football clubs like a quick turnaround when they upgrade their pitches.
During the summer, it took two giant sewing machines five days to stitch the entire Derby pitch, working 24 hours a day. Derby also increased the pitch’s grass area by one metre around the edge and replaced the irrigation system and under-soil heating.
There’s only a short close season for this sort of work. Derby played their final home game of 2015-16 on 16 May and their first game on the new pitch on 6 August, drawing 0-0 with Brighton, another of Brian Clough’s old teams.
On 20 September, Derby faced Premier League giants Liverpool at the Ipro Stadium. Liverpool play their home games on a hybrid pitch too, installed by Desso. Back in Clough’s day, this might have been the sort of game where the sprinkler system accidentally got left on overnight in a crafty attempt to reduce the skill gap between the two teams.
On one of those Baseball Ground mud heaps, there would have been no chance of Jürgen Klopp’s team playing their high-intensity passing and pressing game. Yet if current Derby manager Nigel Pearson tried that trick today, the water would just drain through the surface and out through underground pipes. In football, technology doesn’t always give people the sort of advantage they might want.
Cancer concern over artificial pitches
Thirty sports clubs in the Netherlands have closed their artificial pitches after a toxicology professor at Utrecht University, claimed on Dutch TV, that the pitches should be checked out for potential risks to people’s health. Particularly, cancer.
Earlier this month, Professor Martin Van Der Bergh told the Zembla TV programme that he wouldn’t play on these fields because a proper investigation of potential health risks has not yet been carried out.
The Hague Government has ordered an immediate investigation into the matter. The Dutch football association also responded, saying that more needs to be done to investigate whether carcinogens in these pitches can end up in the bodies of those who use them. But fears that the rubber granules used in the 3G surfaces present a cancer risk are not new.
An artificial '3G' pitch contains synthetic grass-like blades, inserted into a sand base layer and supported by rubber crumb, tiny fragments made from recycled tyres. The rubber crumb prevents wear and tear and soaks up excess water. But it also sprays up during contact, say during a sliding tackle or a dive by a goalkeeper. And this, according to the experts is what causes the problem.
As far back as 2006, a Norwegian study raised the link with cancer as did another, out of Michigan, two years later. In 2013, Dutch scientists expressed concern about using rubber crumb in children’s play areas.
Earlier this year, a University of Washington study confirmed that rubber crumb can contain hazardous levels of toxic chemicals. So did tests carried out at the University of Stirling.
The Washington study claimed that these chemicals, if ingested over a long period of time, can lead to an increased risk of developing cancer. Professor Andrew Watterson form the University of Stirling said that that the extent to which these carcinogenic compounds might be ingested, inhaled or absorbed through the skin during contact with the surface, is not yet known.
Watterson adds: ‘The reports of cancers in young sports people are not being investigated yet to my knowledge. No one knows exactly what the denominator is for this group and no details have been made available on the cancer rates for the age groups and genders involved so no conclusions can be drawn.’
Artificial pitch manufacturers claim that there is no conclusive proof that the surfaces are a health risk. Despite this, some are looking into alternatives. Moulded plastic pellets, elastomers, cork, coconut shell, even recycled Nike shoes. These substitutes, however, are generally more expensive than rubber crumb and it’s not known whether they’re as durable.
Both the US Environment Protection Agency and the Californian Environment Protection Agency’s Office of Environmental Health Hazards are currently looking at the risks. The European Chemicals Agency is also looking at exposures, aiming to identify hazardous materials that may pose a health risk.
The ECA report, out later this year, is also assessing the risk resulting from skin, oral and inhalation exposure. But it is not Andrew Watterson, says, looking at the actual cancer cases.
‘I’m surprised no study has been commissioned in either the US or Europe to explore these cancer cases,’ he says. ‘The absence of evidence is of course not evidence of absence.’
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