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American Journal of Sports Science and Medicine, 2014, Vol. 2, No. 4, 161-165
Available online at http://pubs.sciepub.com/ajssm/2/4/8
© Science and Education Publishing
DOI:10.12691/ajssm-2-4-8
Muscular Activity of Lower Extremity Muscles Running
on Treadmill Compared with Different Overground
Surfaces
Lin Wang1, Youlian Hong2, Jing Xian Li3,*
1School of Kinesiology, Shanghai University of Sport, Shanghai, China
2Department of Sports Medicine, Chengdu Sports University, Chengdu, China
3School of Human Kinetics, University of Ottawa, Ottawa, ON K1N 6N5, Canada
*Corresponding author: jli@uottawa.ca
Received July 04, 2014; Revised July 14, 2014; Accepted July 16, 2014
Abstract The objective of this study is to compare the muscular activity of lower extremity muscles while
running on treadmill and on overground surfaces. A total of 13 experienced heel-to-toe runners participated in the
study. Electromyographic (EMG) data of four lower extremity muscles, including rectus femoris, tibialis anterior,
biceps femoris, and gastrocnemius, were collected using the Noraxon EMG system while running on a treadmill and
on overground surfaces at a running speed of 3.8 m/s. The obtained data were then analyzed. In this study,
throughout the stance phase, the EMG values in the rectus femoris (P<0.01) and the biceps femoris (P<0.05) were
higher while running on overground surfaces than those on a treadmill. The EMG values in the rectus femoris
(P<0.05) and the biceps femoris (P<0.05) were also higher on concrete than those on grass in the stance phase.
Results showed that the muscle activity was significantly different in treadmill running than in overground running.
The difference in muscle activity while running on different overground surfaces was also found in this study.
Kinematic adjustment of the lower extremity may explain the EMG difference while running on different surfaces.
Keywords: running surfaces, muscular activity, Electromyographic, lower extremity, Biomechanics
Cite This Article: Lin Wang, Youlian Hong, and Jing Xian Li, “Muscular Activity of Lower Extremity
Muscles Running on Treadmill Compared with Different Overground Surfaces.” American Journal of Sports
Science and Medicine, vol. 2, no. 4 (2014): 161-165. doi: 10.12691/ajssm-2-4-8.
1. Introduction
Running is one of the most popular sports activities.
People run on different surfaces. Surfaces for overground
running include concrete, asphalt, sports track made from
synthetic rubber, and natural turf [1,2]. Meanwhile,
treadmills are widely used in laboratory settings for
training and research that require control on speed and
slope [3].
The increasing use of treadmills has forwarded
questions on the difference in biomechanics characteristics
between running on a treadmill and on overground
surfaces. To date, perspectives on whether the treadmill-
based analysis of running mechanics can simulate
overground running mechanics remain contradictory [4,5].
Published studies mainly focused on running kinematics
and kinetics. Contradictory results are likewise shown in
the kinematic analysis. Wank et al. found that compared
with running on overground surfaces, treadmill running
exhibits a shorter flight phase, decreased stride length, and
increased cadence at a moderate speed ranging from 3.3
m/s to 4.8 m/s [6]. Other studies found that some
kinematic variables (e.g., hip adduction angle, hip
internal/external rotation, ankle eversion, and maximal
pelvic rotation) of the treadmill gait are slightly different
from those of the overground gait [5,7]. In the kinematic
analysis of a study, no significant difference was found in
vertical ground reaction force between treadmill and
overground running at a constant running speed [7]. In
addition, several studies observed an in-shod plantar
pressure during treadmill and overground running [8,9].
These studies found that compared with overground
running, treadmill running has a lower magnitude of
maximum plantar pressure at the plantar area. Kinematic
changes in the ankle joint complex during treadmill
running attribute the difference in the plantar pressure
[8,9]. Furthermore, the manifestation of biomechanics
changes in treadmill running in the changes in
neuromuscular activation is still under debate [6,8].
When running on different surfaces, runners adapt their
lower extremity kinematics and stiffness to maintain
similar impact forces [10,11]. In previous studies,
researchers found that kinematic adaptation is associated
with neuromuscular adaptation while running on different
surfaces [8,12]. A few studies attempted to identify the
differences in muscular activity while running on different
surfaces [6,8]. In these studies, electromyography (EMG)
was used to measure muscular activation during running.
In several earlier studies, researchers failed to identify the
differences in amplitudes and coordination of EMG-
related parameters between treadmill and overground
162 American Journal of Sports Science and Medicine
running [13,14]. Wank et al. observed similar EMG
patterns of the leg muscles in comparing overground and
treadmill running at speeds of 4 and 6 m/s [6]. In the same
study, researchers reported that the biceps femoris showed
higher magnitude and longer activity duration at ground
contact and swing phase during treadmill running than
other muscles. The vastus lateralis also showed lower
amplitudes at ground contact. Baur et al. found that during
overground running, EMG exhibited a later onset, a later
maximum, and a shorter total time in the peroneus longus
than that in treadmill running, while the soleus showed
higher amplitude during overground running at the push-
off phase [8].
Despite the difference in muscular activity findings
between treadmill and overground running in previous
studies, the types of overground surfaces were not
described. The hardness of overground surfaces affects the
muscular activity of the runner [12]. To date, no
investigation has been conducted on the differences in
EMG parameters when runners run on different
overground surfaces and on the treadmill. Thus, the
present study aims to examine the differences in muscle
activities when running on different overground surfaces
and on the treadmill. The results of this study will
demonstrate advanced differences in muscular activation
while running on a treadmill and on different overground
surfaces, which will determine if treadmill running can be
used to simulate the muscle activity of overground
running.
2. Methods
2.1. Subjects
Thirteen young male students (aged 22.4 ± 3.9 years,
body mass of 63.6 ± 9.2 kg, and body height of 170.6 ±
6.2 cm) volunteered to participate in the study. All
participants were right-leg dominant, heel strikers in
running, and had a shoe size of 41 (European standard).
The participants were experienced treadmill or overground
surface runners and ran at least 20 km per week. Only
male participants were recruited to eliminate gender
differences in the running biomechanics. The participants
had no history of diseases associated with the
neuromuscular system and suffered no sports injuries in
the last six months prior to the study. Prior to the
experiments, the participants were provided an informed
consent. The study was approved by the Ethics Committee
of the local university.
2.2. Running Surfaces and Running Shoes
Concrete and asphalt are the most commonly used
surfaces for recreational and marathon runs. Natural grass
surfaces had been previously examined in the study of
plantar loads while running and performing specific sports
movements. In the present study, three overground
surfaces, namely, concrete (C), synthetic rubber (R), and
natural grass (G) were studied. Natural grass and rubber
surfaces comprise the standard natural grass soccer field
and the standard synthetic rubber running track,
respectively. Treadmill running tests were conducted on a
treadmill (T) (6300HR, SportsArt Fitness, USA).
A pair of new running shoes with European size of 41
(TN600-neutral, ASICS, Japan) was assigned to each
participant. The running tests were performed on each
surface using the said footwear.
2.3. Testing Protocol
During the running trials, the EMG signals were
acquired and transmitted by the Noraxon TeleMyo
(Noraxon USA Inc., Scottsdale, USA) telemetered EMG
system (bandwidth from10 Hz to 350 Hz). The frequency
of the EMG data acquisition was set at 1000 Hz. The
EMG collection was synchronized with the video data
recording using the Ariel Performance Analysis System
(Ariel Dynamics Inc., Trabuco Canyon, USA). The EMG
data were collected from four lower extremity muscles,
namely, rectus femoris, tibialis anterior, biceps femoris,
and gastrocnemius [12]. Before the electrode placement,
the participant’s skin was shaved and cleansed with
alcohol. Bipolar surface electrodes (Noraxon Dual #272,
US) were attached to the participant’s skin at the midline
of the muscle belly [15]. To reduce inconsistency and
inter-subject variability in normalizing the EMG signal
[16], the EMG signal was normalized to a reference
activity rather than to a maximum voluntary contraction.
Four controlled reference postures, namely, squatting,
lower leg raised to 90°, dorsiflexion, and plantar flexion
were implemented to normalize the muscles under study
[17]. The EMG signals in the selected postures were
recorded under submaximal isometric contraction.
The treadmill running test was conducted in an indoor
laboratory. Each participant ran six minutes on a treadmill
at 3.3 m/s for warm-up [18]. Subsequently, they were
instructed to run on the treadmill at a velocity of 3.8 m/s
for 2 min for data collection. Five successful steps of the
right-foot stance phase during the last minute were
measured for data analysis.
The overground running test was conducted on a 30 m
straight runway. The first 15 m of the runway was the
acceleration zone, followed by 5 m (15 m to 20 m) of the
measurement zone where participants ran at a velocity of
3.8 m/s. This velocity was consistent with that employed
in previous studies [1,19]. The velocity was timed using
an infrared timing system (Brower Timing System, USA).
The timers were placed at the start and end points of the
measurement zone. Each participant ran for 6 min on a
standard running track at his preferred velocity to warm
up. After warm up and prior to data collection, each
participant was allowed as many practice trials as
necessary to achieve a smooth running pattern, with
controlled velocity of 3.8 m/s. The trial was accepted
when the running velocity was within 5% of the controlled
velocity on the 5 m measurement zone. On each running
surface, participants completed five successful trials. In
each successful trial, plantar load data of at least one
complete right-foot stance were collected. The right-foot
stance indicated the phase from heel strike to toe push off
of the right foot during running. Five steps on each surface
were used in the data reduction. The order of running
surfaces was randomly assigned to each participant. The
same protocol was used in our previous study [9].
2.4. Data Reduction and Analysis
All EMG raw data were processed by the Noraxon
EMG system. The raw EMG signal was filtered using the
band-pass filter with bandwidth ranging from 20 Hz to
American Journal of Sports Science and Medicine 163
500 Hz, and then the signal was full wave-rectified. By
selecting a complete stride, the magnitude of the signal
recorded from each of the channels was normalized to the
maximum magnitude obtained from the submaximal
isometric contraction tests. The time normalization of the
stance and the swing phases was separately performed for
each of the running trials. Each cycle was divided into
four phases (Montgomery III, Pink, and Perry, 1994). By
definition, one stride or cycle is the period from the initial
contact of one foot to the initial contact of the same foot.
A complete running stride is considered as two steps. Each
step is defined as the initial contact of one foot and then
the initial contact of the contralateral foot. The foot
experiences the support and the swing phases [20]: the
stance (from the right-heel touchdown to the right toe off),
the early swing (from the right toe off to the left-heel
touchdown), the middle swing (from the left-heel
touchdown to the left toe off), and the late swing (from the
left toe off to the right-heel touchdown).
All data are presented as mean (standard deviation, SD).
The comparison of surfaces was performed using
ANOVA for repeated measurement analysis on selected
EMG variables. Significance was at alpha < 0.05, and
Bonferroni adjustment was used to correct multiple
measurements. The 95% confidence intervals (CI) for the
mean difference in each variable among the four surfaces
were calculated to determine the range of differences.
3. Results
Table 1. Mean (SD) of muscle activity parameters (magnitude normalized in ratio)
Muscle & running phase
T
R
G
C
Rectus Femoris Phase 1
0.037 (0.023)
0.213 (0.076)
0.154 (0.045)
0.247 (0.130)
*,#,§,†
Rectus Femoris Phase 2
0.038 (0.022)
0.070 (0.021)
0.042 (0.016)
0.091 (0.039)
Rectus Femoris Phase 3
0.037 (0.019)
0.037 (0.020)
0.030 (0.021)
0.051 (0.052)
Rectus Femoris Phase 4
0.024 (0.005)
0.017 (0.008)
0.030 (0.006)
0.050 (0.009)
Tibialis Anterior Phase 1
0.083 (0.031)
0.105 (0.042)
0.114 (0.061)
0.144 (0.060)
Tibialis Anterior Phase 2
0.066 (0.011)
0.079 (0.024)
0.093 (0.006)
0.140 (0.004)
Tibialis Anterior Phase 3
0.092 (0.022)
0.102 (0.035)
0.100 (0.032)
0.129 (0.022)
Tibialis Anterior Phase 4
0.122 (0.095)
0.113 (0.042)
0.164 (0.140)
0.139 (0.105)
Biceps Femoris Phase 1
0.048 (0.028)
0.133 (0.072)
0.099 (0.062)
0.128 (0.126)
*,#,§,†
Biceps Femoris Phase 2
0.024 (0.012)
0.045 (0.011)
0.057 (0.011)
0.083 (0.025)
Biceps Femoris Phase 3
0.064 (0.053)
0.098 (0.070)
0.102 (0.070)
0.133 (0.086)
Biceps Femoris Phase 4
0.124 (0.107)
0.160 (0.138)
0.102 (0.068)
0.128 (0.080)
Gastrocnemius Phase 1
0.474 (0.311)
0.622 (0.230)
0.609 (0.399)
0.600 (0.405)
Gastrocnemius Phase 2
0.144 (0.031)
0.236 (0.057)
0.174 (0.073)
0.179 (0.045)
Gastrocnemius Phase 3
0.070 (0.043)
0.090 (0.078)
0.052 (0.050)
0.074 (0.054)
Gastrocnemius Phase 4
0.066 (0.018)
0.078 (0.004)
0.128 (0.007)
0.179 (0.008)
Note: T,Treadmill; R, Synthetic rubber; G,Grass; C,Concrete
Phase 1,Stance phase; Phase 2,Early swing; Phase 3,Middle swing; Phase 4,Late swing
*,P < 0.05, T vs. Ta; #, P < 0.05, T vs. G; §, P < 0.05, T vs.C; †, P < 0.05, G vs.C;
Figure 1. The EMG profile of four muscle groups of one stride
164 American Journal of Sports Science and Medicine
In the study, different EMG patterns between treadmill
and overground running were found (Figure 1).
Significant differences were observed in the stance phase
in the rectus femoris and the biceps femoris. Throughout
the stance phase, the EMG values in the rectus femoris
(P<0.01, 95% CI for mean difference, R: T = 0.273 to
0.079, G: T = 0.183 to 0.050, C: T = 0.360 to 0.060) and
the biceps femoris (P<0.05, 95% CI for mean difference,
R: T = 0.183 to 0.010, G: T = 0.139 to 0.030, C: T = 0.231
to 0.070) were higher on overground surfaces than those
on the treadmill. Furthermore, the EMG values in the
rectus femoris (P<0.05, 95% CI for mean difference =
0.179 to 0.007) and the biceps femoris (P<0.05, 95% CI
for mean difference = 0.121 to 0.006) were higher on
concrete than those on grass. No significant differences
were found for all muscles in the swing phases (Table 1).
4. Discussion
In this study, the primary finding was that the muscle
activity of the rectus femoris and the biceps femoris has a
lower magnitude of EMG values in treadmill running than
that in overground running during the stance phase. The
EMG values in treadmill and overground running showed
similar activity patterns during the swing phase.
The result on the rectus femoris was consistent with
that by Wank et al. [6]. Wank et al. found a higher EMG
magnitude of the biceps femoris during the last part of the
ground contact in treadmill running than that in
overground running [6]. This result is in contrast to the
findings in the present study in which a lower EMG
magnitude of the muscle during the stance phase on the
treadmill was found than that on overground surfaces. The
difference in running speed (4 and 6 m/s in Wank et al.’s
study vs. 3.8 m/s in this study) and the division of running
gait phases (three phases in Wank et al.’s study vs. four
phases in this study) may also contribute to the varied
results between the two studies. In treadmill running, the
body is not necessarily pushed forward continuously.
Thus, not much energy is needed to provide the forward
movement of the body’s center of gravity (CG) compared
with that in overground running during the heel
touchdown to the toe-off period. This explanation can be
supported by the kinematic findings [21]. In the stance
phase, significant differences were observed on the
parameters of the trunk angle between treadmill and
overground running. Treadmill running showed less
forward lean of the trunk. As mentioned earlier, this
difference is because, compared with overground running,
no forward movement of the trunk was necessary in
treadmill running and the running speed was maintained
by the treadmill belt. Novacheck proposed that CG can be
moved in front of the support foot in the stance phase by a
greater forward trunk lean, while a greater horizontal GRF
can be exerted on the contact surface [22]. Therefore, in
treadmill running, CG of the runner does not move
forward and less horizontal GRF is needed. This
kinematic characteristic can be reflected by the
observation in the muscle activity. The less horizontal
GRF necessary in treadmill running, the lower is the
magnitude of muscle activity of the rectus femoris and the
biceps femoris in treadmill running than that in
overground running during the stance phase.
Moreover, in the stance phase, the muscle activity of
the rectus femoris and the biceps femoris showed lower
magnitude in grass running than that in concrete running.
The differences in muscle activity levels may be
associated with the stiffness of the running surfaces.
Previous studies showed that the hard surface with high
stiffness level led to the increase in the touchdown impact
force [18,23]. Consequently, a higher force was
transmitted to the leg, and a greater contraction was
required to provide the support. In a recent study, similar
maximal plantar forces were found while running on
different overground surfaces at total foot and different
plantar areas [24]. Several studies found that increased
surface hardness induces kinematic changes in the lower
extremity on the sagittal plane [10,18]. Lower extremity
kinematics and stiffness adaptations to different
overground running surfaces have been interpreted as a
form of active adaptation in maintaining similar impact
forces [10,11,18]. These adaptations included larger ankle
and knee flexion [10] and larger knee and hip flexion at
heel strike on more rigid surfaces [11]. The runner can
adapt kinematic characteristics by adjusting the
musculoskeletal system while running on different
surfaces to maintain similar impact force [10,11,18]. The
findings in the present study may provide advanced
evidence on the muscular adjustment of the lower
extremity when a runner runs on different overground
surfaces.
Overall, significant differences were found in muscular
activities between treadmill and overground running.
Therefore, treadmill running may be considered as a
different movement task that requires a specific muscle
action. Treadmill running may also be proposed as an
effective method for athletic training or physiological
testing in laboratories because of its EMG characteristics
in specific muscles. However, researchers should be
cautious in applying the results from the treadmill test.
The results obtained from the current trend of shoe testing
on the treadmill may not accurately reveal the real
functional response of the shoes when used in overground
running. Moreover, the test results showed that substantial
changes in the lower extremity muscle activity occur in
response to the altered surface during running. Changing
the hardness of the surface can alter the activity of the
lower extremity muscle. By selecting different surfaces for
training purposes, different training effects can be
achieved.
5. Conclusion
The results showed that muscle activity is significantly
different in treadmill running than that in overground
running. Moreover, a difference in muscle activity while
running on different surfaces was found. The kinematic
adjustment of the lower extremity may explain the EMG
difference when running on different surfaces.
Competing Interests
The authors declare that they have no competing
interests.
American Journal of Sports Science and Medicine 165
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