Participation in field sports is an important part of American
culture, and overall levels of participation have increased
dramatically in the past 20 years, as have the number of
injuries to the lower extremities, especially the knees. There
are an estimated 80 000 ACL tears each year in the United
and approximately 50 000 ACL reconstruc-
tions are performed annually, leading to a total cost of these
injuries of almost $1 billion per year.
Although many ACL
injuries are caused by collisions between players, the vast
majority of these injuries—approximately 70%—occur in
including falls, sudden stops while
running, or rapid changes of direction.
From an injury pre-
vention perspective, there are numerous possible causes for
these noncontact ACL injuries, but a primary factor impli-
cated in many of them is the interaction between the player’s
shoe and the playing surface.
Torg and Quedenfeld
were among the first researchers
to document the important role that the interaction between
a shoe and the playing surface has in understanding and
preventing noncontact injuries. They observed that the
number and size of cleats on a shoe were correlated with the
occurrence of knee and ankle injuries in (American) foot-
; less aggressive cleats produced fewer injuries. In a
follow-up study, Torg et al
defined a “release coefficient”
based on the peak torque developed at the shoe-surface
interface, to quantify the injury potential of specific shoe-
Peak Torque and Rotational Stiffness
Developed at the Shoe-Surface Interface
The Effect of Shoe Type and Playing Surface
Glen A. Livesay,*
PhD, Dawn R. Reda,
MS, and Eric A. Nauman,
Department of Applied Biology and Biomedical Engineering, Rose-Hulman Institute
of Technology, Terre Haute, Indiana, the
Department of Biomedical Engineering,
Tulane University, New Orleans, Louisiana, and the
School of Mechanical Engineering,
Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana
Shoe-surface interactions have been implicated in the high number of noncontact knee injuries suffered by athletes
at all levels.
To examine shoe-surface interactions on newer field designs and compare these with more traditional shoe-surface
combinations. The peak torque and rotational stiffness (the rate at which torque is developed under rotation) were determined.
Controlled laboratory study.
A device was constructed to measure the torque versus applied rotation developed between different shoe-surface
combinations. Data were collected on 5 different playing surfaces (natural grass, Astroturf, 2 types of Astroplay, and FieldTurf),
using 2 types of shoes (grass and turf), under a compressive load of 333 N.