Increasing Running Shoe Traction can Enhance Performance

Abstract

The outsole of a running shoe must provide enough traction for the athlete to avoid slipping during running. What is unknown is whether there is any point to designing running shoe outsoles with traction above this minimum required traction. The purpose of this study was to investigate whether performance could be enhanced by increasing the outsole traction of a running shoe. A commercially available running shoe (Control) was compared against the same shoe model with the outsole modified with a higher traction rubber (High Traction). The available traction of each shoe was measured with a traction testing system. Twenty male athletes completed a maximal effort timed running course in both shoes on two different surfaces. When wearing the Control running shoe, the athletes were able to complete the course on an asphalt road surface at maximal effort without slipping. When completing the same course wearing the High Traction shoe, the subjects were able to perform the course even faster. Therefore, the results show that the role of running shoe outsole traction is not to merely provide adequate traction to avoid large scale slips, but can also help athletes enhance performance of high-traction tasks such as accelerations and changes in direction.

Full text

RJTA Vol. 18 No. 2 2014
17
Increasing Running Shoe Traction can Enhance Performance
Jay T. Worobets
1
*, Fausto Panizzolo
2
, Steve Hung
1
, John W. Wannop
1
and Darren J. Stefanyshyn
1
1
Human Performance Lab, Faculty of Kinesiology, University of Calgary, Canada
2
School of Sport Science, Exercise and Health, University of Western Australia, Australia
ABSTRACT
The outsole of a running shoe must provide enough traction for the athlete to avoid
slipping during running. What is unknown is whether there is any point to designing
running shoe outsoles with traction above this minimum required traction. The purpose of
this study was to investigate whether performance could be enhanced by increasing the
outsole traction of a running shoe. A commercially available running shoe (Control) was
compared against the same shoe model with the outsole modified with a higher traction
rubber (High Traction). The available traction of each shoe was measured with a traction
testing system. Twenty male athletes completed a maximal effort timed running course in
both shoes on two different surfaces. When wearing the Control running shoe, the athletes
were able to complete the course on an asphalt road surface at maximal effort without
slipping. When completing the same course wearing the High Traction shoe, the subjects
were able to perform the course even faster. Therefore, the results show that the role of
running shoe outsole traction is not to merely provide adequate traction to avoid large
scale slips, but can also help athletes enhance performance of high-traction tasks such as
accelerations and changes in direction.
Keywords: Footwear, Running Shoe, Outsole, Traction, Performance
1. Introduction
Footwear properties can enhance athletic
performance. For instance, researchers have
shown that reducing running shoe mass can
increase running economy (Catlin &
Dressendorfer, 1979; Divert et al., 2008;
Frederick, 1984), and incorporating properly
engineered carbon fiber insole plates into
footwear can positively affect jump height and
sprint time (Stefanyshyn & Fusco, 2004;
Stefanyshyn & Nigg, 2000; Tinoco et al., 2010;
Toon et al., 2009; 2011).
An aspect of running shoes that could potentially
affect performance is the outsole. The outsole, or
‘tread’, of the shoe is the bottom part of the shoe
that directly contacts the ground. As such, one
important role of the outsole is to provide the
athlete with traction. Clearly, if the outsole of a
shoe provides insufficient traction, the athlete
may slip during running, thus negatively affecting
performance. However, if the outsole traction of a
shoe already provides sufficient traction to avoid
slipping, it is not clear whether there is any
performance benefit if the traction is increased
even further.
Previous published research on running shoe
traction has focused on measuring the traction
(the translational friction coefficient) between
different running shoes and different surfaces
(Haberl & Prokop, 1973; Morehouse & Morrison,
1975; Nigg 1980; Cavanagh & Williams, 1981).
While this information has been invaluable in
furthering the basic knowledge on the topic, a
description is missing in the literature on how
running shoe traction and running performance
are related.
From a biomechanical standpoint, outsole traction
provides a runner with the ability to manipulate
the direction of the resultant ground reaction force
vector. As it is this ground reaction force that
accelerates the runner in the intended direction, it
is theoretically plausible that providing a runner
with more grip could allow the runner to direct
the ground reaction force more advantageously,
* Corresponding author. Tel.: 1 (403) 220 2704
E-mail address: worobets@ucalgary.ca (Jay Worobets)

RJTA Vol. 18 No. 2 2014
18
facilitating faster accelerations and changes in
direction (as when running along a curved path).
Therefore, the purpose of this study was to
investigate whether performance of a maximal
effort running course composed of accelerations
and changes in direction could be enhanced by
increasing the outsole traction of a running shoe.
2. Methods
Twenty male recreational athletes with either
distance or track running experience were
recruited for this study (age 32.6 ± 10.2 yr, height
176.1 ± 2.7 cm, mass 73.6 ± 7.5 kg). All subjects
were a US 9 shoe size and free from recent injury
or pain. Informed written consent was obtained
from all subjects prior to data collection in
accordance with the University of Calgary’s
Conjoint Health Research Ethics Board.
The two shoes tested in the study were obtained
from adidas AG. The control shoe was the
commercially available adidas adiZERO adios
racing flat, which had a stiff polymer outsole
material under the forefoot (Figure 1). The
experimental ‘High Traction’ shoe was the same
adiZERO adios model, however, during the
manufacturing process the forefoot outsole was
built with a soft rubber material obtained from the
tire manufacturer Continental AG (Figure 1). This
rubber from the tire manufacturer was softer,
heavier, and was purported to have higher traction
than the outsole material found on the
commercially available shoe. Therefore, the two
shoes tested in the study varied only in forefoot
outsole material and tread pattern, and the overall
shoe mass (Control 202 g, High Traction 209g).
Fig. 1. Photographs of the Control shoe (left) and
High Traction shoe (right).
The available traction of each of the test shoes
was quantified by using a custom portable
footwear traction testing system. The system
consisted of a foot last mounted under a moveable
load cell. The foot last was mounted at an angle of
20° of plantar-flexion such that only the forefoot
of the shoe would be in contact with the ground.
A shoe was placed on the foot last, a vertical load
of 580 N was applied on top of the load cell to
contact the shoe with the ground, and then the
shoe was dragged across the ground at a speed of
250 mm s-1 by an automated electrical motor.
During this movement, horizontal forces were
collected by the load cell at a frequency of 2000
Hz. These forces were then used to calculate the
peak translational traction coefficient between the
shoe and ground. A more detailed description of a
similar system can be found in Kuhlman et al.
(2010), where traction coefficients were measured
between cleated shoes and artificial turf surfaces.
Prior to the study, the portable footwear traction
testing system was validated in-lab with the use of
a Kistler force platform embedded in the ground
sampling at 2000 Hz. With the traction tester
positioned over the force platform, forces were
simultaneously measured by both systems as a
shoe was dragged across the force platform
(Figure 2). The calculated peak traction
coefficients from the two systems were found to
be in good agreement (differences were less than
1.0%).
Fig. 2. Traction coefficients obtained from the
portable traction tester and force plate
during validation. Each curve is the
average of 5 trials
A short duration maximal effort timed running
course was used to evaluate athletic performance
(Figure 3). The course was designed to
incorporate a curved acceleration, an abrupt
change in direction, and a straight acceleration.

RJTA Vol. 18 No. 2 2014
19
The subjects started from rest, then after tripping
a first set of infra-red timing lights sprinted with
maximal effort along an 8 meter radius quarter
circle to a second set of timing lights. The
subjects were instructed to come to a stop as
quickly as possible once they heard the ‘beep’
from the second set of timing lights, then turn
around and sprint straight towards a third set of
timing lights 8 meters away. The total time to
complete the course was recorded.
Fig. 3. The timed running course. Dotted lines
indicate timing light gates
Testing occurred outdoors on two different
surfaces under dry conditions; an asphalt road
surface, and a tartan track and field surface. In
order to quantify the available traction between
the shoes and surfaces, ten trials per shoe were
collected with the traction tester on each surface.
Each subject completed two performance testing
sessions, one session per surface. The two test
sessions for any subject were not completed on
consecutive days, and the order that the surfaces
were tested in was randomized for each subject.
During a test session, after a warm up to get used
to the course, each subject completed five trials in
each shoe condition on each surface, for a total of
ten trials. The shoe condition worn for the first
trial was randomized, then after each trial the
subject changed shoes. The subjects were allowed
as much time between trials to recover as they
required in order to minimize effects of fatigue.
The averages of the five trials for each shoe were
calculated for analysis.
Additionally, each subject’s perceived
performance in each shoe condition was
quantified using visual analog scales (VASs). The
VAS was a 14 cm horizontal line, with the left end
of the line stating “Worst traction imaginable”,
and the right end of the line stating “Best traction
imaginable”. After every trial, the subjects were
required to indicate their perceived performance
by marking a vertical line on the VAS. The VAS
scores were quantified by measuring the distance
from the left end of the scale to the subject’s mark
in centimeters. These values were then
normalized to the total length of the scale by
dividing by 14 cm and multiplied by 100 to be
expressed as a percentage. During testing, the
course times of the subjects were not revealed to
them.
Independent t-tests were used to identify any
statistically significant differences in available
traction between shoes, and paired t-tests were
used to compare course times and VAS scores
between shoes. The level of significance was set
at α=0.05.
3. Results
The average values for the peak available traction
coefficients, course completion times, and VAS
scores for the two surfaces are shown in Table 1.
Statistically significant differences between shoe
conditions are indicated with bold p-values.
Table 1. Average (SD) values of the variables of
interest.
Control
High
Traction
p-value
Asphalt Surface
Traction Coeff. 1.25
(0.05)
1.41
(0.05)
< 0.01
Course Time [s]
5.78
(0.47)
5.73
(0.43)
< 0.01
VAS Score [cm]
7.2
(2.8) 9.0
(1.9) 0.01
Tartan Surface
Traction Coeff. 1.38
(0.05) 1.40
(0.05) 0.54
Course Time [s]
5.73
(0.52)
5.75
(0.47)
0.29
VAS Score [cm]
8.6
(1.9)
9.2
(1.6)
0.06
On the asphalt road surface, the available traction
of the High Traction shoe was statistically
significantly higher than that of the Control shoe
(1.41 vs. 1.25). The subjects completed the course
significantly faster in the High Traction shoe
compared to the Control shoe (5.73 s vs. 5.78 s).
The VAS scores were statistically significantly
higher (indicating more perceived traction) for the

RJTA Vol. 18 No. 2 2014
20
High Traction shoe than the Control shoe (7.2 cm
vs. 9.0 cm).
On the tartan track surface, there were no
statistically significant differences identified
between the High Traction and Control shoes for
any of the three analyzed variables. On this
surface, the High Traction shoe did not have more
traction than the Control, and the subjects
performed the same in both shoe conditions.
4. Discussion
The purpose of this investigation was to
investigate whether performance could be
enhanced by increasing the outsole traction of a
running shoe. Intuitively, decreasing traction
could cause an athlete to slip. However, it is not
clear if providing a runner with increased traction
could allow the athlete to move faster. Currently,
the published opinion on the role of running shoe
outsole traction is to provide sufficient grip to
avoid slipping during running (Frederick, 1984).
It may be that if the traction was increased
beyond this ‘sufficient’ value, an additional role
may be to allow the athlete to perform
high-traction tasks better (such as accelerating
and changing direction).
The results of this study suggest that the role of
running shoe traction is not to merely provide
adequate traction to avoid large scale slipping, but
can also help athletes maximize performance. The
subjects were able to complete the running course
on a dry asphalt road surface statistically
significantly faster when wearing the High
Traction shoe compared to the Control shoe. The
running course was composed of high-traction
tasks; curved acceleration, abrupt deceleration,
and linear acceleration, all at maximal effort. The
Control shoe provided enough traction to allow
the subjects to complete the course at maximal
effort without large scale slipping. However,
when the High Traction shoe was worn, the
subjects were able to perform the course even
faster.
Similar results that relate footwear traction to
performance in other sports have been recently
reported. Luo & Stefanyshyn (2011) showed that
increasing the available traction of basketball
shoes up to a point allowed athletes to accelerate
faster both along curved and straight paths on an
indoor surface. Müller et al. (2010) showed that
soccer cleat traction affected the performance of
soccer players who executed a running/cutting
slalom course on synthetic turf. In both of these
studies, athletes were able to perform
high-traction maneuvers faster due to increased
footwear traction. The present study found the
same result, but this time with running shoes on a
dry outdoor asphalt road surface.
The mechanism by which the increased traction
allowed the subjects to perform better is unknown
and warrants further study. It could be that greater
traction allows an athlete to direct the ground
reaction force more horizontally, which would
increase accelerations and decelerations in the
transverse plane. Or, it could be that even though
large scale slipping in the Control shoe did not
happen, micro-slipping between the shoe and
surface was occurring. If this was the case, the
higher traction outsole may have reduced this
amount of micro-slipping. However, this is
merely speculation and was not verified in this
experiment.
The experimental High Traction shoe condition
used in this study was constructed by integrating
rubber obtained from a tire manufacturer
(Continental AG) into the outsole. This rubber
was purported by the manufacturer to have
enhanced traction characteristics. When the
available traction of the two shoe conditions were
measured on the asphalt road surface with the
traction tester, this was in fact found to be the
case; the High Traction shoe had statistically
significantly higher traction than the Control shoe.
However, when tested on the tartan track surface,
no difference in traction was found between the
two shoes.
It is unknown exactly why the soft rubber used in
the High Traction shoe increased traction on the
asphalt road surface but did not on the tartan track
surface. One possible explanation could be that on
a smooth hard surface such as asphalt, the outsole
of the shoe dictates the traction characteristics,
but on a rough soft surface such as a tartan track,
it is the surface that dictates the traction
characteristics. Or, it could be that the rubber
obtained from the tire manufacturer was
specifically designed to enhance traction on the
type of surface that the tires would be driven on; a
hard surface similar to asphalt. Nevertheless, the

RJTA Vol. 18 No. 2 2014
21
results on both surfaces support the main finding
of the study; on asphalt the High Traction shoe
provided more traction and the athletes performed
faster, while on the tartan track surface the High
Traction shoe did not provide more traction, and
the performance of the athletes was not affected.
Although the increase in performance found in
this study was real (i.e. statistically significant),
the average magnitude of the increase was
relatively small (0.05 s). It is unknown whether
this improvement in performance would translate
to a meaningful advantage for an athlete
competing in a race over an asphalt surface.
However, it is important to note that the VAS
results showed that the subjects were actually able
to perceive the extra traction offered by the High
Traction shoe, despite being blinded to the shoe
conditions. This should not be discounted as a
potential important benefit to an athlete; there
may be positive psychological implications when
a user is wearing footwear that s/he is more
confident in, although this is merely speculation.
On the asphalt surface, the rubber in the High
Traction shoe increased the available traction
from 1.25 to 1.41. It may be that the course
performance could have been further improved if
the traction was increased even higher. However,
there is evidence that increasing footwear traction
only enhances athletic performance up to a point;
if traction is further increased above a certain
critical threshold, no additional improvements are
made to performance (Luo & Stefanyshyn, 2011).
However, without further testing, it is unknown
how close the High Traction shoe was to this
critical traction threshold. It must be noted that
the traction coefficients measured in this study are
not absolute values; they are specific to the
measurement method employed. Previous studies
have documented how the boundary conditions of
a traction test can influence the value of the
traction coefficient obtained (Kuhlman et al. 2010;
Rheinstein et al. 1978; Valiant, 1987; 1993;
1994).
5. Conclusion
The role of running shoe outsole traction was
previously thought to be important only for
avoiding large scale slipping during running. In
this study, when wearing a control running shoe
athletes were able to complete a course composed
of high-traction maneuvers on a dry asphalt
surface at maximal effort without slipping. When
the subjects completed the same course wearing a
shoe with increased outsole traction, the subjects
were able to perform the course even faster.
Therefore, these results show that the role of
running shoe outsole traction is not to merely
provide adequate traction to avoid large scale
slips, but can also help athletes enhance
performance of high-traction tasks such as
accelerations and changes in direction.
The results of this study suggest that if the goal of
a running shoe manufacturer is to help an athlete
maximize performance, the outsole of the shoe
should be designed to offer more traction than is
sufficient to just avoid slipping. It is currently
unknown at what point increasing traction no
longer has a positive effect on performance.
Future work employing similar methods to this
study could help establish a minimum outsole
traction value (a value required to avoid slipping)
and a maximum outsole traction value (a value
above which performance is no longer increased).
This information would serve as a useful
guideline for footwear manufacturers during
outsole design and development.
Acknowledgements
The authors would like to thank adidas AG for
providing the test shoes for the study.
REFERENCES
[1] Catlin M.J. & Dressendorfer R.H. 1979,
‘Effect of shoe weight on the energy cost of
running’, Medicine & Science in Sports &
Exercise, vol. 11 pp. 80.
[2] Cavanagh P.R., Hinrichs R.N., Williams K.R.
1980. ‘Testing procedure for the 1981
Runner’s World Shoe Survey. Runner’s
World, pp. 38-49.
[3] Divert C., Mornieux G., Freychat P., Baly L.,
Mayer F., Belli A. 2008, ‘Barefoot-shod
running differences: Shoe or mass effect?’
International Journal of Sports Medicine,
vol. 29, no. 6, pp. 512-518.
[4] Frederick E.C. 1984, ‘Physiological and
ergonomics factors in running shoe design’,
Applied Ergonomics, vol. 15, no. 4, pp.
281-287.
[5] Haberl R. & Prokop L. 1973, ‘Def einfluss

RJTA Vol. 18 No. 2 2014
22
physikalischer materialgroessen auf die
stuetzphase beim lauf’, Oesterreichishes
Journal fur Sportsmedizin, vol. 3, pp. 3-17.
[6] Kuhlman S.M., Sabick M.B., Pfeiffer R.,
Cooper B., Forhan J. 2010, ‘Effect of
loading condition on the traction coefficient
between shoes and artificial turf surfaces’,
Proceedings of the Institution of Mechanical
Engineers Part P: Journal of Sports
Engineering and Technology, vol. 224, no. 2,
pp. 155-165.
[7] Luo G. & Stefanyshyn D.J. 2011,
‘Identification of critical traction values for
maximum athletic performance’, Footwear
Science, vol. 3, no. 3, pp. 127-138.
[8] Morehouse C.A. & Morrison W.E. 1975,
The artificial turf story: a research review.
Pennsylvania State University: HPER Series
No 9.
[9] Müller C., Sterzing T., Lange L., Milani T.
2010, ‘Comprehensive evaluation of
player-surface interaction on artificial soccer
turf’, Sports Biomechanics, vol. 9, no. 3, pp.
193-205.
[10] Nigg B.M. & Denoth J. 1980,
Sportplatzbelaege. Juris Verlag, Zurich.
[11] Rheinstein D.J., Morehouse C.A., Niebel
B.W. 1978, ‘Effects on traction of outsole
composition and hardnesses of basketball
shoes and three types of playing surfaces’,
Medicine & Science in Sports & Exercise,
vol. 10, no. 4, pp. 282-288.
[12] Stefanyshyn D.J. & Fusco C. 2004,
‘Increased shoe bending stiffness increases
sprint performance’, Sports Biomechanics,
vol. 3 no. 1, pp. 55-66.
[13] Stefanyshyn D.J. & Nigg B.M. 2000,
‘Influence of midsole bending stiffness on
joint energy and jump height performance’,
Medicine & Science in Sports & Exercise,
vol. 32, no. 2, pp. 471-476.
[14] Tinoco N., Bourgit D., Morin J.B. 2010,
‘Influence of midsole metatarsophalangeal
stiffness on jumping and cutting movement
abilities’, Proceedings of the Institution of
Mechanical Engineers Part P: Journal of
Sports Engineering and Technology, vol.
224, no. 3, pp. 209-217.
[15] Toon D., Vinet A., Pain M.T.G., Caine M.P.
2011, ‘A methodology to investigate the
relationship between lower-limb dynamics
and shoe stiffness using custom-built
footwear’, Proceedings of the Institution of
Mechanical Engineers Part P: Journal of
Sports Engineering and Technology, vol.
225, no. 1, pp. 32-37.
[16] Toon D., Williams B., Hopkinson N., Caine
M. 2009, ‘A comparison of barefoot and
sprint spike conditions in sprinting’,
Proceedings of the Institution of Mechanical
Engineers Part P: Journal of Sports
Engineering and Technology, vol. 223 no. 2,
pp. 77-87.
[17] Valiant G.A. 1987, ‘The relationship
between normal pressure and the friction
developed by shoe outsole material on a
court surface’, Journal of Biomechanics, vol.
20, no. 9, pp. 892.
[18] Valiant G.A. 1993, ‘Friction – Slipping –
Traction’, Sportverletz Sportschaden, vol. 7,
no. 4, pp. 171-178.
[19] Valiant G.A. 1994, ‘Evaluating outsole
traction of footwear’. In: Proceedings of
the Eighth Biennial Conference of the
Canadian Society for Biomechanics,
Calgary (Canada). University of Calgary,
pp. 18-24.

Reproduced with permission of the copyright owner. Further reproduction prohibited without
permission.