Effects of Playing Surface and Shoe Type on ACL Tears in Soccer Players Melissa Mansfield
Advisor: Professor Bucinell
Introduction and Background
Results
The knee is one of the most frequently injured joints in the body.
Studies have shown there are over 150,000 anterior cruciate
ligament (ACL) tears in the United States each year [1].
Approximately 70% of these injuries occur in non‐contact situations
where there are high compression forces and the knee is slightly
rotated [2]. The ACL is a primary stabilizer of the knee during this
motion and experiences high levels of torque. It is believed that ACL
tears in soccer players are influenced by the type of shoe worn and
the surface being played on.
It was determined that the playing surface had a greater influence
of the measured torque than the shoe type. In addition, some
artificial turf samples produced less torque and some produced
more torque than the natural grass samples. Generally, the torque
increased with playing surface in the following order: Gym Turf, Old
Turf, Grass, New Turf 1.5” and New Turf 1.0”. The torque also
increased when the shoe type was varied as follows: Round
Studded, Turf Shoe, Bladed Studded and Soft Grounds. A summary
of these results is represented by the plot in Figure 4.
Experimental Procedures
Testing was carried out on a MTS servo‐hydraulic tension‐torsion
machine. A prosthetic lower limb fitted with various soccer cleats
was mounted to a load cell. A metal fixture was designed to apply
the load across the forefoot of the shoe and to keep the heel raised
off the playing surface to comply with ASTM standards [3]. Playing
surface samples were secured to a fixture allowing for precise and
reproducible rotation as seen in Figure 1. A 225 lbs (1000 N) normal
load and a 45° rotation at a rate of 45°/s were applied. Four types
of soccer cleats were tested as seen in Figure 2. Five playing
surfaces were tested: soil‐based Kentucky bluegrass (Grass),
thatched artificial turf with 1/2” blades and foam backing (Gym
Turf), ten year old slit film artificial turf with rubber infill (Old Turf),
and a new slit film artificial turf surface with 1” deep rubber infill
(New Turf 1”) and 1.5” deep rubber infill (New Turf 1.5”). The
artificial turf surfaces are shown in Figure 3. Five trials were
conducted for each combination and the order in which the various
shoe‐playing surface combinations were tested was randomized to
insure that factors that were not included in the study did not
confound the data.
Gym Turf: 378 in‐lbs
Old Turf: 480 in‐lbs
Grass: 556 in‐lbs
New Turf 1.5”: 618 in‐lbs
New Turf 1.0”: 702 in‐lbs
Round Studded: 477 in‐lbs
Turf Shoe: 517 in‐lbs
Bladed Studded: 574 in‐lbs
Soft Grounds: 624 in‐lbs
Figure 4: Box whisker plot showing how the maximum torque varies from shoe type and playing surface. The mean torque values for all trials conducted are displayed in the corners of the plot.
Discussion
Although our experimental set‐up fails to reproduce the complex
forces that occur during an injury to the ACL, we assume that an
increased amount of tension would be created in the ACL
proportional to the increased torque between various shoe‐playing
surface combinations. The Grass samples stabilized the torque at
approximately 550 in‐lbs for all shoe types tested on it. This could
have resulted from the grass surface’s ability to deform when it
experiences torque greater than 550 in‐lbs. Gym Turf and Old Turf
experienced less torque than Grass which was due to the shoes
ability to slip; however, this is not desirable when playing. The New
Turf 1.0” samples experienced significantly more torque than grass,
but when the sample was filled with more rubber infill to make New
Turf 1.5”, the resulting torque values were very similar to that of
Grass. This shows that there are playing surfaces that have
comparable torque to that produced on Grass; however, artificial
surfaces do not have the ability to continuously deform.
References
Figure 1: Shows the experimental set‐up
Figure 2: Shows the shoe types tested: Round Studded (top left), Bladed Studded (top right), Soft Ground (bottom left) and Turf Shoe (bottom right)
Figure 3: Shows the artificial turf samples: Gym Turf (left), Old Turf (middle) and New Turf (right).
1. Coleman, Erin. "Statistics on ACL Injuries in Athletes." LIVESTRONG.COM. N.p., 21 Oct. 2011.
2. Griffin LY, Agel J, Albohm MJ, “Non‐contact anterior cruciate ligament injuries: risk factors and prevention strategies.” J Am Acad Orthop Surg. 2000;8:141‐150.
3. American Society for Testing and Materials.2009. Annual Book of ASTM Standards. Vol.15.07 End Use Products. Standard test method for traction characteristics of the athletic shoe‐
sports surface interface. F‐2333‐04. ASTM, West Conshohocken, PA
Acknowledgements
A special thanks to Professor Bucinell, Professor Rice, Cydnee Somera, the machine shop technicians and my family.