The authors have declared that no competing interests exist.
The global popularity of soccer has led to widespread tendency towards this sport. Because of the convenience of using artificial surfaces, the rapid growth of using these surfaces led to concerns about the declining performance of the players. The aim of this comprehensive review is to study the difference between the performance of players on different playing surfaces and the risk factors for use of artificial turf compared to natural grass. A literature search of valid scientific databases such as Science Direct, PubMed and Jstor by searching keywords was performed. In total, more than 6,000 articles were retrieved. After the preliminary selection process, the final analysis was performed on a total of 76 articles.
Mechanical properties of artificial grass have a significant effect on the average time of sprinting, the best time of sprinting and maximum speed. The numbers of sliding tackles on artificial turf were lower compared to natural grass. Artificial turfs exposed hardness, elasticity and high friction. The characteristics of artificial grass have changed over time and increased the probability of injuries. There was no significant difference between the overall risks of acute injuries in soccer players performing on artificial turf compared to natural grass. The amateur, young and female soccer players had rated lower injuries on artificial grass. But the rate of injuries in elite soccer players were higher on artificial grass and hence they are not found of playing on such playing surfaces.
Soccer is a very popular sport all over the world with various actions such as change of direction, starts, stops, jumps and kicks
The use of third generation artificial grass is officially accepted by FIFA and UEFA in international tournaments. However, there are concerns that some of the mechanical properties of artificial sports-surfaces may be associated with acute and chronic sports injuries
The use of artificial turf has provided different operating conditions compared to natural grass such as speeding up and increasing the bounces of the ball and various impacts on player movement pattern. The performance qualities of soccer players during exercise and competition on the synthetic turfs are affected by low shock absorbance and high surface temperature. This would lead to injuries, particularly of the lower extremities. The purpose of this study is to review the literature and studies on the impact of artificial turf on the soccer players’ performance, the nature of the risk factors and injuries compared to those of natural grass surfaces in order to minimize the injuries and achieve maximum benefits of training and competition on these types of surfaces.
Comprehensive search was undertaken from September 2016 to February 2017 through valid scientific databases such as Science Direct, PubMed and Jstor by searching keywords such as "soccer", "playing surface", "artificial turf", "natural grass" and "artificial turf risk factors". Articles published from 1975 to 2016 were selected.. Afterwards, the title and abstracts of articles were reviewed. Non-English articles, repetitive topics, studies on non-human samples, simulation, measurement tools of mechanical properties and articles with the purpose of treatment and rehabilitation were excluded. The selection criteria were as follows: (1) studies comparing artificial and natural turf, (2) articles related to the mechanical properties of artificial surfaces for soccer, and (3) studies of mechanisms or risk factors of injuries on artificial turf and comparison of their rate and nature with those of natural grass. Afterwards, the bibliographies of the selected articles were observed to select and add additional articles that may have not been detected through the preliminary search.
The database search yielded about 6000 articles relevant to the objectives of this article. After the preliminary selection process and addition of further papers based on the bibliography of the initial articles, a total of 76 papers were chosen and reviewed. The process of search, selection and extraction of the papers is depicted in
The literature dedicated to the impact of artificial grass on the performance of players include investigations on shock absorption, hardness, friction, impacts on the ball (change in the ball’s rolling resistance
This study firstreviews the literature pertaining to the effect of playing surface on the performance of players, and then assesses the results of articles in relation to the risk factors affecting the incidence of injury on artificial turf.
Artificial turf has lower shock absorption than natural grass, so switching the training from natural grass to artificial grass can be uncomfortable and lead to more foot pain in young soccer players
Friction performs a major role in players’ ability to make fast changes in direction, but too much friction can impose excessive force on bones, muscles and joints
A study by Tay
McLaren et al (2012) studied the performance degradation of artificial turf with age and found that the friction effect is associated with interaction between skin abrasion and ball resistance. He reported that growth of moss and algae on the surface reduces the surface-shoe friction and makes the surface slippery; and that the ball roll distance is affected by bending resistance, friction, and orientation of the fibers
Traction is a key parameter for measuring comfort, performance and risk of injury
A comparison of different types of artificial grass by Sa´nchez
The ability of a surface to withstand the movements is directly related to its impact absorption properties
A study conducted by Brito
A study conducted by Strutzenberger
Dragoo
Study | Subject | Level of Performance | Methods | Results |
Sex, Age | Elite | Evaluation of movement pattern and technics with Motion Analyzer | no difference in terms of running activities and technical performance;less sliding tackles and more short passes on artificial turf | |
72 Male 21 Female | - | SERG impact hammer | As the penetration of boot increases, the traction increase; on artificial turf the stud provided low traction. | |
6 different cleat | Elite | Cutting maneuver, sprint and 180º turn, jump-head-land | Frontal plane moments and ground reaction forces were increased in softer and higher traction surfaces. | |
16 Men | - | - | Different artificial turfs had different transitional traction.Traction decreased on Long fiber with high thickness infill | |
22 Men | Elite | The reduction in maximum torque of hamstrings immediately, 24 hours and 48 hours after the test was higher on natural grass. | ||
13 Men | Elite | Cutting maneuver | 1. more stiffness, 2. Higher friction, 3. Higher metabolic cost | |
99 Men | Amateur | Conditioning test and Isokinetic | Players feel more comfortable on harder and stiffer systems | |
18 Men | - | - | Turfs that have no infill have the highest friction, and those with full gravel or rubber infill have equally lower friction |
In a survey conducted using a 0-10 scale (in which 0 represented the absolute superiority of artificial turf, 10 represented the absolute superiority of natural grass, and 5 represented equal quality), male soccer players expressed very negative opinions about artificial grass (8.3) and cited poorer ball control and the need for greater physical effort as its disadvantages. However, female soccer players believed that there is no difference between natural grass and artificial turf in terms of ball control, ball movement and physical effort
Ford
Internal factors associated with the occurrence of injuries on artificial turf are related to material, installation and maintenance of turf. The difference in turf performance is mainly due to factors such as age and method of installation rather than infill material
Cheng
Iacovell
For an average player, surface-shoe traction has a correlation with the incidence of injury
The use of artificial turf can be associated with environmental and health risks, but the complexity of involved chemical compounds make this issue difficult to assess
Although the pitch performance is influenced by the weather, amateur soccer players prefer artificial turf to natural grass, because natural grass is dry and hard during summer, and muddy or frozen in winter. The critical weather conditions for artificial grass are “hot weather” and “rain”
From the perspective of players, the ultimate objective of for improvement of playing surfaces should be to maximize performance and comfort and minimize occurrence of injuries. The most common method of assessment of injury on artificial turfs
Study | Subject | Level of | Training or match | Type of injury | Incidence (No per 1000 hours) | |
Performance |
|
|||||
Sex, Age | college and university football teams | Training | Hip/groin | 5.29 | 5.15 | |
Knee | 2.3 | 2.23 | ||||
Ankle | 3.2 | 3.48 | ||||
Male | college and university football teams | Training | Hip/groin | 2.5 | 3 | |
Knee | 3.28 | 3 | ||||
Ankle | 2.88 | 2.43 | ||||
106 team | professional | Match | Hip/groin | 3.6 | 1.9 | |
Knee | 3 | 2 | ||||
Ankle | 3.1 | 2.2 | ||||
Female | Elite | Match | Hip/groin | 2.21 | 1.85 | |
Knee | 3.83 | 3.99 | ||||
Ankle | 3.24 | 4.45 | ||||
136 team | Elite | Match | Hip/groin | 0.44 | 0.18 | |
Knee | 0.29 | 0.56 | ||||
Ankle | 0.15 | 0.76 | ||||
Male | Amateur | Match | Hip/groin | 5.2±0.4 | 3.2±1 | |
Knee | 5.6±0.3 | 4.6±0.9 | ||||
Ankle | 8.4±0.4 | 4.3±0.8 | ||||
14 team | Elite | Match | Hip/groin | 14.2 | 7.4 | |
Knee | 12.8 | 3.7 | ||||
Ankle | 8.8 | 14.2 | ||||
professional | Training | Hip/groin | 0.29 | |||
Knee | 0.22 | |||||
Ankle/Achilles tendon | 0.14 | |||||
613 male | professional | Match | Hip/groin | 0.37 | ||
Knee | 0 | |||||
Ankle/Achilles tendon | 0.18 | |||||
Age 25±5 | Elite | Match | Contact | 3.8 | 7.87 | |
Non-contact | 11.4 | 10.23 |
Bianco
There have been many studies dedicated to comparing injuries occurred on natural grass and artificial turf (
Hägglund
In support of these results, the study of Meyers (2010) on location, duration, and severity of injury showed that traumatic injuries are significantly more frequent on natural grass than on artificial turf (almost twice as much)
To assess the damage caused by sliding on artificial turf, Peppelman
The studies on relation of artificial turf and upper extremity injuries are quite few in numbers. De Putter
The use of artificial turfs in soccer pitches is on the rise and today many players, especially the youth, train and compete on these surfaces. Although artificial turfs have passed the FIFA tests, degradation of their qualities with time can affect the performance or even injure the players. Over time, infill layers of these turfs gets compressed and quality of their shockpads degrades, and these developments lead to increasing hardness of surface. These changes result in elongated artificial grass fibers and therefore increased friction between shoe and surface. They also increase the rotational traction and thus escalate the likelihood of injury on artificial turf. Most results provided in the literature suggest that the use of artificial turf does not increase the rates of injury, especially acute injuries, during competition. However, there have been reports of higher rates of injury during training on artificial turf as compared to natural grass. In addition, comparing the results of the literature in relation to performance of players showed that, for elite players, the rate of injury have been higher on artificial turf than on natural grass, but this has not been true for women, amateur players, and young players (from toddlers until youth), so for these groups are safer to use artificial turf. This difference may be due to low rates of injury, especially traumatic injuries, in youth soccer. And since the rate of non-traumatic injuries has been lower on artificial turf than on natural grass, the lower rate of injury in this group of players is expected. Furthermore, elite players are heavier and generate more power than amateur and college players, so they produce more torque and traction.
In studies conducted with the aim of assessing the opinions of players in regard to training and competition on the artificial turf, elite players stated that, in comparison to natural grass, artificial turf is “too hard / harder”, “flatter” and “more abrasive” and “thinner”. But the average scores given by amateur soccer players showed that in their opinion, artificial turfs are better than natural grass, except in the category of risk of abrasion. Thus, the results show that players’ perception of pitch properties depends on their experience from different levels of play during youth and adulthood.
Most studies in the literature have reported high rates of ankle injuries on artificial turf, so injury prevention strategies should take this issue into consideration. Also, pitch temperature triggers different requirements for players, and both coaches and players should be aware of these differences. Health consequences of heat-stress in artificial grass during summers require precautionary-preventive measures for players and reassessment of true utility of transition from natural grass to artificial turf.