Field Hockey And Artificial Turf

Dr. Ak. Joy Singh *

A match during 14th Dr Kanti Mukherjee Memorial Invitation Hockey Tournament 2012-13 :: Pix - Jinendra Maibam

Hockey is an ancient sport thought to be the forerunner of all 'stick and ball' games. The modern game of hockey is played in 132 countries around the world and is second only in popularity to soccer as a team sport. The introduction of synthetic surfaces has significantly changed the sport of field hockey. Since being introduced in the 1970s, competitions in western countries are now mostly played on artificial surfaces. This has increased the speed of the game considerably, and changed the shape of hockey sticks to allow for different techniques, such as reverse stick trapping and hitting. Due to the cost of synthetic pitch installation, India and Pakistan have lost their once dominant position in international competitions.

Artificial turf, or synthetic turf, is a man-made surface manufactured from synthetic materials, made to look like natural grass. It is most often used in arenas for sports that were originally or are normally played on grass, however, it is now being used on residential lawns and commercial applications, as well.

David Chaney headed the team of researchers who created the famous artificial turf. Artificial turf first came to prominence in 1965, when Astro Turf was installed in the newly-built Astrodome in Houston, Texas. The use of Astro Turf and similar surfaces became widespread in the 1970s and was installed in both indoor and outdoor stadiums used for baseball and gridiron football in the United States and Canada. Maintaining a grass playing surface indoors, while technically possible, is prohibitively expensive, while teams who chose to play on artificial surfaces outdoors did so because of the reduced maintenance cost, especially in colder climates with urban multi-purpose stadiums.

The commonly used pitch in field hockey is the Dunfermline's pitch. It has a base of expanded polypropylene, a foamy material originally developed as a shock absorber for the car industry. The grass is also made of lubricated polyethylene fibres sewn in a rubberised plastic mat. But they are shorter and more densely packed when compared with soccer fields. The whole thing is then "infilled" with a 4-centimetre layer of sand and rubber granules, which keeps the fibres upright and provides the right level of shock absorbency and deformability and are also interspersed with short, curly, spring-like fibres that keep the blades upright. The finishing touch is an 8-millimetre filling of rubber granules.

Field hockey artificial turf differs from soccer and football artificial turf in the way that it does not try to reproduce a grass 'feel', being made of shorter fibres similar to the ones used on Dunfermline's pitch. This shorter fibre structure allows the improvement in speed brought by earlier artificial turfs to be retained. This development in the game is however problematic for many local communities who often cannot afford to build two artificial pitches : one for field hockey and one for other sports. The International Hockey Federation and manufacturers are driving research in order to produce new pitches that will be suitable for a variety of sports.

Pitch categories

Unfilled : Often called "water-based", the pile is unfilled. The pitches require wetting, hence the name "water-based", often via prolonged showering with pitch-side water cannon prior to their use and occasionally during half-time intervals depending on the prevailing atmospherics. They are favoured by most sports since they offer more protection for players by minimising the abrasive effect created by the sand. These pitches form the majority of the elite level field hockey pitches in use today.

Sand-dressed : The pile of the carpet is filled to within 5-8 mm of the tips of the fibre with fine sand. The sand cannot be seen. It can be confused with unfilled pitches.

Sand filled : The piie of the carpet is filled almost to the top with sand. The sand makes the pitch rough and harder. In comparison to water-based pitches or minimal sand-dressed pitches, ball speed across the surface is often noticeably slower.

Advantages

1. Artificial turf can be a better solution when the environment is particularly hostile to natural grass. An arid environment or one where there is little natural light are examples.

2. Artificial turf pitches can last up to ten years.

3. Some artificial turf systems allow for the integration of fibre-optic fibres into the turf. This would allow for lighting or advertisements to be directly embedded in a playing surface, or runway lighting to be embedded in artificial landing surfaces for aircraft.

Disadvantages

1. Some artificial turf requires infill such as silicon sand and or granulated rubber made from recycled car tyres. These materials may carry heavy metals which can leach into the water table.

2. Periodic disinfection is required as pathogens are not broken down by natural processes in the same manner as natural turf. This notwithstanding, recent studies suggest certain microbial life is less active.

3. Turf toe is a medical condition which is often associated with playing on artificial turf pitches.

4. Friction between skin and some types of artificial turf causes abrasions and/or burns to a much greater extent than natural grass. This is an issue for some sports like hockey in which sliding maneuvers are common and clothing does not fully cover the limbs.

5. Artificial Turf tends to be much hotter than natural grass when exposed to the sun.

There are other practical advantages to the use of synthetic surfaces in hockey. The International Hockey Federation has developed performance standards for hockey pitches based on ball rebound, ball run and deviation, impact response, surface friction, dimensions, slope, smoothness, colour, gloss, watering, porosity and surface health.

Anecdotal evidence suggests that ankle inversion injuries, meniscal problems and the prevalence of shin soreness, knee pain and lower back problems have increased with the more widespread use of synthetic surfaces. The abrasive nature of synthetic playing surfaces has meant that lacerations are also more frequent.

The natural grass surface contributes to a greater cushioning effect and less strain to the lower limbs by absorbing 10% more energy on impact than synthetic turf. The only study to compare the rate of injury on synthetic surface to that of grass is Jamison and Lee (1989). The authors reported that although the overall number of injuries sustained on Astroturf was greater than on grass, the joint injuries to the lower limb were more prevalent on grass surfaces (53%) than on Astroturf (37%). More research is needed to determine whether synthetic surfaces put the joints of the lower limb at greater risk of injury.