RESEARCH ARTICLE
Effect of a Wide Stance on Block Start
Performance in Sprint Running
Mitsuo Otsuka*, Toshiyuki Kurihara, Tadao Isaka
Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga, 525–8577,
Japan
* otsuka-a@st.ritsumei.ac.jp
Abstract
This study aimed to clarify the effect of widened stance width at the set position during the
block start phase in sprint running on kinematics and kinetics at the hip joint and block-
induced power. Fourteen male sprinters volunteered to participate in this study. They per-
formed three block-start trials with a normal stance width (25 ± 1 cm, normal condition) and
a widened stance width (45 ± 2 cm, widened condition) at the set position. The block start
movements were recorded at 250 Hz with high-speed cameras and the ground reaction
forces at 1250 Hz with force plates. During the block phase in the widened condition, the hip
abduction and external rotation angles in both legs were significantly larger and smaller,
respectively, than those in the normal condition. The positive peak value of the hip power in
the rear leg was significantly greater in the widened condition than that in the normal condi-
tion. However, no significant difference was seen in the normalized block-induced power
between the widened and normal conditions. We conclude that a widened stance width at
the set position affects the hip-joint kinematics and rear hip power generation during the
block start phase, but no effect on the block-induced power when considering sprinting per-
formance during the whole block start phase.
Introduction
During the pushing phase on starting blocks, the average value of external power in an anterior
direction to translate the whole-body centre of mass (COM; hereafter, block-induced power) is
important for a great performance in the 100-m dash [1,2]. This is associated with the exten-
sion of front and rear legs. Sprinters are permitted to adjust the anteroposterior position and
inclination of both starting blocks in accordance with the regulations for athletes [3]. Several
previous studies have clarified the effect of different body postures at the set position on the
subsequent sprinting motion during the block start phase [4–8]. For instance, relative to the
elongated start, bunched and medium starts shorten the pushing duration during the pushing
phase on the starting block, thereby shortening the subsequent sprinting time at 5 m and 10 m
[7,8]. This may be due to the optimal position of body segments, which enhances the power
generation of the lower limbs and block-induced power during the block start phase [4,5].
PLOS ONE | DOI:10.1371/journal.pone.0142230
November 6, 2015
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OPEN ACCESS
Citation: Otsuka M, Kurihara T, Isaka T (2015) Effect
of a Wide Stance on Block Start Performance in
Sprint Running. PLoS ONE 10(11): e0142230.
doi:10.1371/journal.pone.0142230
Editor: Miklos S. Kellermayer, Semmelweis
University, HUNGARY
Received: July 6, 2015
Accepted: October 18, 2015
Published: November 6, 2015
Copyright: © 2015 Otsuka et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any
medium, provided the original author and source are
credited.
Data Availability Statement: All relevant data are
within the paper and its Supporting Information files.
Funding: This work was supported by the Kozuki
Foundation 2011-9-1 to MO (http://www.kozuki.or.jp/
jigyou/spresearch/list2011_09_spres.html). The
funder had no role in study design, data collection
and analysis, decision to publish, or preparation of
the manuscript.
Competing Interests: The authors have declared
that no competing interests exist.
Sprinters extend both legs during the block start phase from a bending position [2,9]. Peak
extension angular velocity of the front and rear hips, contributes to the block-induced power
during the block start phase, unlike that of the knee and ankle [2]. This rapid hip extension
might be associated with greater power generation at the hip joint, thereby providing greater
block-induced power during the block start phase. The hip power generation is larger than
those at the knee and ankle of the front and rear legs during the block start phase [5]. These
findings suggest that the hip extensor kinetics is a key contributor to high block-induced
power. This leg extension motion during the block start phase is similar to the double-legged
squat motion [10]. Biomechanical analysis of the squatting motion has revealed that lengthen-
ing the mediolateral distance between feet (140% of shoulder width) contributes to stronger
isometric contractions in lower limb muscles [11]. This widened stance width enhances the
mean electromyography value of the gluteus maximus during a squat [12–14]. The stance
width at the set position of the block start has been reported to be 23 ± 1 cm [15]; this is shorter
than the stance width in previous studies on widened stance width in squatting [11–14]. These
studies may indicate that a widened stance width during the block start phase would enhance
block-induced power during the block start phase attained by a greater hip joint power. Never-
theless, sprinters may not be able to select enough stance width at the set position for greater
block-induced power using the current competition blocks [3]. For instance, the mediolateral
width of starting blocks in overall dimension is 30 cm (RM-150, Seiko, Tokyo, Japan). This
width is narrower than the stance width in squats used to enhance muscle strength [11].
Thus, further investigation of squatting to block start is required to elucidate the effect of a
wide stance width on block-induced power. This information would help in reconsidering
block start rules [3], developing new starting block designs, and aiding sprinters in the appro-
priate placement of starting blocks in the future. This study aimed to clarify the effect of wid-
ened stance width at the set position during the block start phase on hip kinematics, hip
kinetics and block-induced power. Our hypotheses were as follows: 1) widened step width dur-
ing the block start phase would lead to sprinters changing their hip position and enhance
block-induced power attained by the high hip power generation, and 2) widened step width
during the block start phase would affect the relationship between changes in block-induced
power and those in the hip power generation.
Materials and Methods
Participants
Fourteen male sprinters (mean ± standard deviation [SD]; age: 21.1 ± 1.2 years, body mass:
64.5 ± 3.9 kg, height: 1.76 ± 0.04 m) volunteered to participate in this study. Three participants
were international-level sprinters, who were finalists in the National Championship. All partic-
ipants were sprint specialists with training experience of 6 years (8.4 ± 2.4 years), and the
average personal best 100-m time was 10.99 ± 0.40 s (range: 10.21–11.65 s).
The experimental protocol was approved by the Research Ethics Committee Involving Liv-
ing Human Subjects at Ritsumeikan University (BKC-human-2011-011). Each participant pro-
vided written informed consent before study participation. The individual in this manuscript
has given written informed consent (as outlined in PLOS consent form) to publish these case
details.
Experimental procedure
The participants were asked to perform a 10-m sprint on an indoor track, exerting maximum
effort from a crouching position, with a widened (45 ± 2 cm, widened condition, Fig 1A, S1
Video) and normal (25 ± 1 cm, normal condition, Fig 1B, S2 Video) stance width (mediolateral
A Wide Stance on Block Start Performance
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distance between midpoints of first and fifth metatarsals of feet). The participants were
instructed to start after a gun signal by a starter [3]. The stance width in the widened condition
corresponded to 140% of shoulder width during a squat at widened stance width [11,13]. Each
participant performed three trials each with normal and widened stance width using their own
spike shoes, and the order of trials in both conditions was randomized. To reduce the effect of
body size and crouching position type on block performance, the anteroposterior distance of
the starting blocks was adjusted to 12% of each participant’s height (21 ± 1 cm) so as to be cor-
responded with the bunched start [7,8,16]. The anteroposterior distance between the feet in a
bunched start is closer to that of a squat motion relative to those of medium and elongated
starts. Throughout the experiment, the block angles of front and rear legs were set at 40° and
42°, respectively [4]. The starting blocks were securely anchored to the synthetic track surface
on two separate force plates (0.40 m × 0.60 m; TF-4060-B; Tech-Gihan, Inc., Kyoto, Japan).
Before the experimental trials, an appropriate 15-min warm-up including jogging and stretch-
ing and at least three sprints in each stance width condition were performed.
Data collection
Data on the participants’ sprinting movement and ground reaction force (GRF) during the
block start phase were captured simultaneously. A total of 36 retro-reflective markers sized 12
mm were attached on the pelvis and lower limbs, and the three-dimensional locations of the
markers were recorded using a 16-camera motion capture system (Raptor-E digital; Motion
Analysis Corporation, Santa Rosa, CA, USA) sampling at 250 Hz. The GRF data from legs
were separately measured by positioning a total of 2 force plates (TF-4060-B; Tech-Gihan, Inc.,
Kyoto, Japan), arranged in two rows of two each, sampling at 1250 Hz. The sprinting time was
measured based on signals from the gun (EP; Molten Inc, Hiroshima, Japan) and photocell
Fig 1. A postero-superior view of the set position during the block start phase. (A) Set position in the widened condition. (B) Set position in normal
condition.
doi:10.1371/journal.pone.0142230.g001
A Wide Stance on Block Start Performance
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(E3G-R13; Omuron Inc., Kyoto, Japan) set at 2.0-m mark, and were synchronized with the
GRF data.
Data processing
GRF data were not filtered [17]. We used a vertical GRF threshold of 10 N to determine the
instant of take-off from the starting blocks. We then used these readings to divide the block
start phase into the double-stance and single-stance phases (Fig 2).
The marker trajectory data were filtered using a fourth-order, zero-lag, low-pass Butter-
worth filter, and the cut-off frequency was set at 10 Hz [15]. A 7-segment rigid body model
including the pelvis, thighs, shanks, and feet was created. The segmental data were calculated
using mass properties based on cadavers [18]. The locations of the center of mass and inertial
properties were obtained using a mathematical model [19].
For comparison between different sprinters, the dimensionless [20] normalized block-
induced power was considered as the best indicator of sprinting performance during the block
start phase (hereafter, normalized block-induced power) [1,2]. So as to clarify the relationship
between changes in block-induced power and those in the hip power generation, the dimen-
sionless normalized block-induced power (PN) was calculated as follows:
PN ¼ P=ðm g3=2l1=2Þ
ð1Þ
where m is the mass of the sprinter, g is the acceleration due to gravity, and l is the leg length of
the sprinter. Block-induced power (P) was calculated as follows [1,2]:
P ¼ mðv2
f  v2
i Þ=ð2 DtÞ
ð2Þ
Fig 2. Definition of the double-leg and single-leg stance phases during the block start phase. The block start phase was divided into double-leg and
single-leg stance phases based on the instant of rear-leg take-off. The black solid line represents the pelvis and front leg, the black dashed line represents
the rear leg, and the grey line represents the other segments that were not analyzed in this study.
doi:10.1371/journal.pone.0142230.g002
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where vi and vf are the anteroposterior velocities of COM at the start (here the vi = 0 m/s) and
end of the block start phase, respectively, and Δt is the pushing duration during the block start
phase. Here, the vf is equal to the GRF impulse of the anteroposterior component normalized
by body mass during the block start (hereafter, normalized anteroposterior impulse, IN). The
IN was calculated as follows [21]:
IN ¼
Z t2
t1
apGRFSum dt=m
ð3Þ
where t1 and t2 are the times at which force application begins and ends, respectively, and
apGRFSum is the anteroposterior component of the sum of GRFs from the legs during the block
start phase. The normalized front-block-induced power, normalized rear-block-induced
power, and normalized anteroposterior impulses in front and rear legs were calculated, after
adjusting for Eqs (1), (2) and (3) based on the number of force plates. Mean value of anteropos-
terior and mediolateral accelerations of COM during the block start phase (mean anteroposter-
ior acceleration (apCOMacc) and mean mediolateral acceleration (mlCOMacc), respectively)
was calculated as follows:
apCOMacc ¼ apGRFSum=m
ð4Þ
mlCOMacc ¼ mlGRFSum=m
ð5Þ
where apGRFSum and mlGRFSum are anteroposterior and mediolateral components of sum of
GRFs vector from the legs, respectively. Reaction time, pushing durations in front and rear legs
during the block start phase, sprint times up to 2.0 m with the reaction time were calculated.
Hip angle, moment and power data were calculated using an algorithm in Visual 3D
(v4.86.0; C-motion, Inc., Germantown, MD, USA). The locations of the center of rotation of
the hip [22], knee [23], and ankle [24] were estimated from anatomical landmarks using a pre-
dictive approach. In each pelvic [24], thigh [24], shank [23], and foot [24] anatomical coordi-
nate system, the x-axis represented the extension–flexion axis of segment rotation, the z-axis of
the distal frame represented the external–internal rotation axis, and the axis orthogonal to the
previous two at any given instant in time (y-axis) represented the abduction–adduction axis.
Hip extension, abduction, and external rotation angles of front and rear legs were calculated
using a hip joint coordinate system based on the x-y-z rotation sequence [24]. Knee and ankle
joint coordinate systems were created using methods of Grood and Suntay [23] and Wu et al.
[24], respectively. The hip extension moments of the front and rear/swing legs were calculated
using a standard inverse dynamics approach [25], and were normalized by body mass (Mhip):
positive value indicates extension moment whereas negative value indicates flexion moment.
The hip extension angular velocity (ωhip) was calculated by Winter’s method: positive value
indicates extension angular velocity whereas negative value indicates flexion angular velocity
[25]. The hip joint power (Phip) for all sprinters was calculated as follows:
Phip ¼ Mhipohip
ð6Þ
Positive power results when the hip joint moment acts in the same direction as the angular
velocity of the hip joint (concentric action). Negative power results when the hip joint moment
acts in the opposite direction as the angular velocity of the hip joint (eccentric action). We used
cubic spline interpolation to normalize these values with respect to time, with 100% represent-
ing the time of the block start phase.
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Changes in normalized block-induced power were calculated (ΔNormalized block-induced
power), and changes in the normalized block-induced power by legs as well as changes in the
mean positive value of hip joint power in the widened condition relative to normal condition
were calculated at each double- and single-stance phases (ΔNormalized block-induced power,
ΔNormalized front-block-induced power, ΔNormalized rear-block-induced power, ΔFront-hip
power generation, and ΔRear-hip power generation, respectively). These changes of variables
in the widened condition relative to those normal condition (Δvar) were calculated as follows:
Dvar ½% ¼ ðvarW=varN  1Þ  100
ð7Þ
where varW and varN are mean values of time-series variables during each phase in the widened
and normal conditions, respectively. Normalized block-induced powers in the two conditions
to calculate ΔNormalized block-induced, ΔNormalized front-block-induced and ΔNormalized
rear-block-induced powers were calculated adjusting Eqs (1), (2) and (3) based on the phase
and number of force plates. For instance, when calculating the block-induced power for ΔNor-
malized front-block-induced power during the double-stance phase in the widened condition,
vi is 0 m/s, vf is the anteroposterior impulse on a force plate exerted by the front foot divided by
body mass during the double-stance phase, and Δt is the duration during the double-stance
phase in the widened condition.
Statistical analysis
For all parameters, the mean value of all three trials in each condition was used for further anal-
ysis [2]. All parameters are shown as mean ± SD. We calculated the intraclass correlation coef-
ficient (ICC(1,3)) for all parameters among three trials. The Lilliefors test was used to assess
normality of variables. In the case of normally distributed samples, paired t-tests were used to
assess the differences in the variables, and in the remaining, the Wilcoxon test was used for
paired samples. Pearson’s correlation coefficient (r) was used to assess the relationships of
changes in variables. Two-way repeated-measure analysis of variance and the post-hoc tests
were used to assess the different effects of two conditions and legs on the variables (condition
[widened and normal] x leg [front and rear]). The level of significance was set at P < 0.05.
Results
Table 1 shows the results of sprinting performance. Of the study participants, no significant
difference in normalized block-induced power was seen between the widened and normal con-
ditions (Fig 3). No significant difference was seen in the anteroposterior impulse, mean antero-
posterior acceleration, reaction time, and duration of the block start phase between the two
conditions. No significant difference was seen in the sprint time up to 2.0 m between the two
conditions. All ICC(1,3) in sprinting performance exceeded 0.700 expect for reaction time
(widened condition: ICC(1,3) = 0.626; normal condition (ICC(1,3) = 0.355).
The hip extension angle in the front leg was not significantly different between widened and
normal conditions during the double- and single-stance phases (Fig 4A). In contrast, the hip
extension angle of the rear leg in the widened condition was significantly larger than that in the
normal condition at the end of double-stance phase and the subsequent maximum extension
angle (Fig 4B). The hip abduction angle in both legs in the widened condition was significantly
larger than that in the normal condition during the block phase (Fig 4C and 4D). The hip
external rotation angle of both legs in the widened condition was significantly lesser than that
in the normal condition during the double-stance phase (Fig 4E and 4F).
No significant differences were seen in the hip extension moments in both legs during the
double-stance phase (Fig 5A and 5B), while the hip extension moment in the widened
A Wide Stance on Block Start Performance
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condition was less than that in normal condition at the end of the single-stance phase. While
no significant differences were seen in the hip extension angular velocity in the front leg during
the block start phase (Fig 5C), the peak values of the hip extension and flexion angular velocity
was significantly greater in the widened condition than that in the normal condition (Fig 5D).
While no significant differences were seen in the hip power of the front leg between two condi-
tions (Fig 5E), the positive peak value of the hip power of the rear leg in widened condition was
significantly larger than that in the normal condition during double–stance phase (Fig 5F).
ΔNormalized block-induced power during the block start phase significantly related to that
during the double-stance phase (r = 0.668; P < 0.01), but did not significantly relate to that
during the single-stance phase (r = −0.021; n.s.). During the double-stance phase, this ΔNor-
malized block-induced power significantly related to the ΔNormalized rear-block-induced
power (r = 0.793; P < 0.01), but did not significantly relate to the ΔNormalized front-block-
induced power (r = 0.390; n.s.). During the double-stance phase, ΔNormalized rear-block-
induced power significantly related to the ΔRear-hip power generation (r = 0.947; P < 0.01).
Discussion
This study aimed to clarify the effect of widened stance width at the set position during the
block start phase in sprint running on kinematics and kinetics at the hip joint, and block-
induced power. During the block phase, the hip abduction and external rotation angles in both
legs and peak hip power generation in rear leg in the widened condition were significantly
changed compared to those in the normal condition. However, in the widened condition, no
significant changes in normalized block-induced power were seen compared to that in the
Table 1. Mean ± SD, range and reliability of sprinting performance during the block start phase and the subsequent sprinting time in widened and
normal conditions.
Parameter
Generator
Widened condition
Normal condition
Δ%
Mean ± SD
Range
ICC
Mean ± SD
Range
ICC
Mean ± SD
Range
Normalized block-induced
power
Both legs
0.543 ± 0.051
0.461–0.663
0.886
0.539 ± 0.053
0.461–0.668
0.891
0.9 ± 5.3
−8.5–10.8
Front leg
0.219 ± 0.023†
0.187–0.259
0.826
0.241 ± 0.042†
0.183–0.344
0.864
−7.5 ± 13.7†
−24.8–27.9
Rear leg
0.130 ± 0.030*
0.091–0.191
0.954
0.113 ± 0.034
0.042–0.161
0.875
22.6 ± 37.0
−9.7–126.7
Anteroposterior impulse
(Ns/kg)
Both legs
3.20 ± 0.20
2.94−3.57
0.961
3.20 ± 0.18
2.98–3.53
0.938
−0.1 ± 2.3
−5.8–3.4
Front leg
2.03 ± 0.11*†
1.89–2.25
0.924
2.14 ± 0.14†
1.95–2.41
0.929
−4.6 ± 5.9†
−14.1–5.5
Rear leg
1.15 ± 0.16*
0.89–1.40
0.910
1.05 ± 0.22
0.55–1.30
0.705
12.1 ± 18.7
−13.1–60.2
Pushing duration during the
block start phase (s)
Both legs
0.330 ± 0.025
0.292–0.368
0.952
0.334 ± 0.031
0.298–0.420
0.946
−0.9 ± 4.5
−12.4–4.1
Front leg
0.330 ± 0.025†
0.292–0.368
0.952
0.334 ± 0.031†
0.298–0.420
0.946
−0.9 ± 4.5
−12.4–4.1
Rear leg
0.180 ± 0.023
0.144–0.224
0.896
0.175 ± 0.034
0.132–0.276
0.932
3.7 ± 8.7
−18.8–13.6
Mean anteroposterior
acceleration (m/s2)
―
9.73 ± 0.59
8.73–10.82
0.843
9.65 ± 0.72
8.10–11.03
0.923
1.0 ± 4.6
−6.2–12.8
Mean mediolateral
acceleration (m/s2)
―
−0.70 ± 0.47*
−1.56–−0.14
0.927
−0.57 ± 0.41
−1.52–−0.05
0.924
50.0 ± 65.1
−43.5–202.0
Reaction time (s)
―
0.180 ± 0.023
0.144–0.224
0.626
0.179 ± 0.016
0.154–0.206
0.355
0.6 ± 9.0
−16.7–18.6
Sprint time up to 2 m (s)
―
0.810 ± 0.043
0.738–0.906
0.836
0.797 ± 0.046
0.734–0.900
0.883
1.7 ± 5.1
−4.8–15.7
*Signiﬁcant difference from normal condition (P < 0.05).
†,§ Signiﬁcant difference from rear leg (P < 0.05).
doi:10.1371/journal.pone.0142230.t001
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normal condition. This suggests that the response to widened stance width on the normalized
block-induced power was not remarkable.
Previous studies have reported a significant effect of body posture in the sagittal plane on
block performance [5,7,8]. A lower block angle (40°) leads sprinters to a 3.6% higher block-
induced impulse than a higher block angle (65°) [5]. Other previous study has reported that
the duration during the block start phase of the elongated start was 9.8% and 11.6% longer
than that of medium and bunched starts, respectively [7]. In this study, the hip abduction and
internal rotation angles of the front and rear legs during the double-stance phase were larger
with a widened stance width than with a normal stance width; therefore, there was a change in
the body position. However, no significant difference was seen in the sprinting performance,
including the normalized block-induced power during the block start (−0.9 ± 5.2%), between
the widened and normal conditions. These suggest that the changes in the set position that are
related to the stance width have a lesser effect on the block performance relative to those related
to the anteroposterior position and block angles.
We focused specifically on the hip power generation, which is considered as the key power
for enhancing normalized block-induced power in lower limbs, rather than the power at the
knee and ankle [2,5]. During the double-stance phase, the hip joint in the front and rear legs
were generated power to induce hip extension, and during the single-stance phase, the hip in
the rear leg was generated power to induce hip flexion. This was corresponding with the find-
ings of the previous studies [5,9]. When the stance width is increased from narrow to wide dur-
ing the squatting motion, the hip extensor muscle activity [12–14,26] and the maximum
strength in lower limbs [11] increase. Demura et al. [11] compared the leg muscle strength
Fig 3. Normalized block-induced power in widened and normal conditions. The bold solid line indicates
the mean value of normalized block-induced power in all participants, and the thin dashed lines indicate the
normalized block-induced power in each participant (n = 14).
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Fig 4. Changes in the hip angles during the block start phase normalized with respect to time. (A) Hip extension angles in front leg. (B) Hip extension
angle in rear leg. (C) Hip abduction angle in front leg. (D) Hip abduction angle in rear leg. (E) Hip external rotation angle in front leg. (F) Hip external rotation
angle in rear leg. The black and grey lines indicate the mean (bold) ± SD (thin) of the time-series data of the front and rear/swing legs in widened and normal
A Wide Stance on Block Start Performance
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between narrow (5 cm) and wide (140% width of the shoulders) stance widths in a squat. They
found that the exerted maximum lower limb force in wide stance width was greater than that
in narrow stance width. Similarly, in this study, the peak power generation at the hip in the
rear leg was greater during the double-stance phase in the widened condition than that in the
normal condition. This was due to enhancing the hip extension angular velocity in the rear leg.
During the double-stance phase in the widened condition, hip in the rear leg was abducted and
internally rotated, which was not the case in the normal condition. Perhaps this changed a
property of the muscle contraction in hip extensor muscles during the double-stance phase
and enhanced the muscle’s contraction velocity, which associates with the hip extension angu-
lar velocity, in the widened condition. In addition, the ΔRear-hip power generation was signifi-
cantly associated with the ΔRear-block-induced normalized block-induced power, indicating
that our second hypothesis was accepted in the rear leg. This suggests that those who preferred
a widened stance width at the set position could increase the hip power generation in the rear
leg by the optimal hip position and could enhance the normalized block-induced power during
the double-stance phase. These findings supported the previous study demonstrating the
importance of the rear leg [2].
However, when considering sprinting performance during the whole block start phase, no sig-
nificant difference was seen in all sprinting performances between the two conditions. The block
start phase involves the single-stance phase in which sprinters have to generate power with sin-
gle-leg stance, in contrast to the squat motion. Therefore, it can be considered that during the sin-
gle-stance phase in the widened condition, sprinters must push the block to a different direction
relative to the normal condition. Indeed, mean mediolateral acceleration was less in the widened
condition than in the normal condition, suggesting that the sprinter’s COM leaned toward the
first step (rear leg) side during the single-stance phase. Thus, our first hypothesis in this study
was rejected and did not correspond with the findings for the squatting position [11].
There are two limitations in this study. First, the number of combinations among stance
width, block angles, and anteroposterior distance were limited for the starting blocks. The stan-
dardized set up was prepared with block angles and anteroposterior distance between the
blocks. Therefore, each sprinter probably was not allowed to create their individual optimal set
up for the starting blocks and probably could not perform their best block start in the normal
condition. Moreover, the stance width in block start was not normalized by each participant’s
body characteristics in the normal or widened conditions. We did not perform normalizations
by body characteristics because the same stance width is conventionally used for all sprinters in
competitive races, which is corresponded with that in normal condition. These might affect
sprinting performance during the block start phase, changes in variables in the widened condi-
tion relative to the normal condition, and reliability of the results. However, the number of exper-
imental trials should be small because the participant cannot repeatedly perform the sprint starts
with maximal effort (no more than six trials) [27]. We could prepared only two conditions at the
set position during the block start phase, and participant performed a total of six block-start tri-
als. This was because of the unavoidable number of conditions as the block start experiment. Sec-
ond, this study was conducted without the familiarization with the widened stance width in the
block start. All participants were sprint specialists with enough training experience, suggesting
that they were familiar with the set position in the normal condition relative to the widened
conditions. These angles at the initial and end instants of double- and single-leg phases and at the instant when the peak value occurs were compared
between the two conditions. Significant differences between the two conditions are shown as * (P < 0.05). Significant difference between the front and rear
legs in widened condition are shown as † (P < 0.05) and that in normal condition are shown as § (P < 0.05). The vertical dashed line indicates the instant of
rear leg take-off during the block start phase.
doi:10.1371/journal.pone.0142230.g004
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Fig 5. Changes in the hip moment, angular velocity, and joint power normalized with respect to time. (A) Hip extension moment in front leg. (B) Hip
extension moment in rear leg. (C) Hip extension angular velocity in front leg. (D) Hip extension angular velocity in rear leg. (E) Hip joint power in front leg. (F)
Hip joint power in rear leg. The black and grey lines indicate the mean (bold) ± SD (thin) of the time-series data of the front and rear/swing legs in widened and
A Wide Stance on Block Start Performance
PLOS ONE | DOI:10.1371/journal.pone.0142230
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condition. Even with extensive training in the widened condition before the experimental trial,
the normal condition would be optimal to enhance the block-induced power relative to the wid-
ened condition. Despite these limitations, we have reported some new information that can serve
as baseline data for future studies on developing the newly designed starting block.
In conclusion, a widened stance width at set position which we prepared in this study
affected the hip-joint kinematics in both legs and hip power generation in the rear leg during
the block start phase. However, when considering sprinting performance during the whole
block start phase, there were no significant effect of the widened stance width on block-induced
power and the subsequent sprint time.
Supporting Information
S1 Video. Trial in the widened condition.
(WMV)
S2 Video. Trial in the normal condition.
(WMV)
Author Contributions
Conceived and designed the experiments: MO. Performed the experiments: MO. Analyzed the
data: MO. Contributed reagents/materials/analysis tools: MO TI. Wrote the paper: MO TK TI.
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Effect of a Wide Stance on Block Start Performance in Sprint Running.
Otsuka, Mitsuo,Kurihara, Toshiyuki,Isaka, Tadao