Push-off forces in elite short track speed skating

Abstract

This study performed an analysis of the push-off forces of elite-short-track speed skaters using a new designed instrumented short-track speed skate with the aim to improve short-track skating performance. Four different skating strokes were distinguished for short-track speed skaters at speed. The strokes differed in stroke time, force level in both normal and lateral directions, and the centre of pressure (COP) on the blade. Within the homogeneous group of male elite speed skaters (N = 6), diversity of execution of the force patterns in the four phases of skating was evident, while skating at the same velocities. The male participants (N = 6) with a better personal record (PR) kept the COP more to the rear of their blades while hanging into the curve (r = 0.82, p < 0.05), leaving the curve (r = 0.86, p < 0.05), and entering the straight (r = 0.76, p < 0.10). Furthermore, the male skaters with a better PR showed a trend of a lower lateral peak force while entering the curve (r = 0.74, p < 0.10). Females showed a trend towards applying higher body weight normalised lateral forces than the males, while skating at imposed lower velocities.

Full text

Full Terms & Conditions of access and use can be found at
http://www.tandfonline.com/action/journalInformation?journalCode=rspb20
Sports Biomechanics
ISSN: 1476-3141 (Print) 1752-6116 (Online) Journal homepage: http://www.tandfonline.com/loi/rspb20
Push-off forces in elite short-track speed skating
Eline van der Kruk, Marco M. Reijne, Bjorn de Laat & DirkJan (H) E. J. Veeger
To cite this article: Eline van der Kruk, Marco M. Reijne, Bjorn de Laat & DirkJan (H) E. J.
Veeger (2018): Push-off forces in elite short-track speed skating, Sports Biomechanics, DOI:
10.1080/14763141.2018.1441898
To link to this article: https://doi.org/10.1080/14763141.2018.1441898
© 2018 The Author(s). Published by Informa
UK Limited, trading as Taylor & Francis
Group
Published online: 30 May 2018.
Submit your article to this journal
Article views: 180
View Crossmark data

SPORTS BIOMECHANICS, 2018
https://doi.org/10.1080/14763141.2018.1441898
Push-o forces in elite short-track speed skating
Elinevan der Kruka, Marco M.Reijnea, Bjornde Laatb and DirkJan (H) E. J.Veegera,c
aDepartment of Biomechanical Engineering, Delft University of Technology, Delft, The Netherlands; bDutch
National Speed Skating Federation, Utrecht, The Netherlands; cHuman Movement Sciences, Vrije Universiteit
Amsterdam, Amsterdam, The Netherlands
ABSTRACT
This study performed an analysis of the push-o forces of elite-short-
track speed skaters using a new designed instrumented short-track
speed skate with the aim to improve short-track skating performance.
Four dierent skating strokes were distinguished for short-track speed
skaters at speed. The strokes diered in stroke time, force level in
both normal and lateral directions, and the centre of pressure (COP)
on the blade. Within the homogeneous group of male elite speed
skaters (N=6), diversity of execution of the force patterns in the four
phases of skating was evident, while skating at the same velocities.
The male participants (N=6) with a better personal record (PR) kept
the COP more to the rear of their blades while hanging into the curve
(r=0.82, p<0.05), leaving the curve (r=0.86, p<0.05), and entering
the straight (r=0.76, p<0.10). Furthermore, the male skaters with a
better PR showed a trend of a lower lateral peak force while entering
the curve (r=0.74, p<0.10). Females showed a trend towards applying
higher body weight normalised lateral forces than the males, while
skating at imposed lower velocities.
Introduction
Short-track speed skating is a form of competitive ice speed skating where multiple skaters
compete on a short (111m) oval ice track. Skaters ride the curves of this oval at very high
velocities, challenging the high centrifugal forces. Applying the right skating technique is
crucial to pass these curves and maintain position in the group during a match. However,
little is known on the biomechanical background of the short-track skating technique. It
is therefore unclear what the ideal technique is and therefore also what to correct for in
athlete skaters.
Although biomechanical research on short-track speed skating is limited, there has been
much research done on the technique of long-track speed skating. However, the technique
of long-track speed skating signicantly diers from that in short-track. In the long-track
discipline skaters make six to eight symmetric strokes at the straight part, before entering
KEYWORDS
Engineering; performance;
force measurement;
techniques
ARTICLE HISTORY
Received 11 September 2017
Accepted13 February 2018
© 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License
(http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium,
provided the original work is properly cited, and is not altered, transformed, or built upon in any way.
CONTACT Eline van der Kruk E.vanderkruk@tudelft.nl
OPEN ACCESS

2 E. VAN DER KRUK ET AL.
the curve, whereas short-track speed skating is mainly skating curves. Since the curves in
long-track speed skating are wider, and the skaters wear klapskates instead of xed skates,
also these techniques dier from the short-track discipline.
e motion of a short-tracker at speed can be divided into four phases: entering the
curve (EC), hanging into the curve (C), leaving the curve (LC) and entering the straight
(ES). Apart from which skating technique, it is also not clear which phase is most critical
for performance. ese issues could be addressed by measuring the push-o forces of a
skater. For short-track, there are no data available yet on the force patterns or force levels
applied during skating for these four phases.
In long-track speed skating, an instrumented klapskate has been developed, measuring
the push-o forces in normal and lateral direction and determining the centre of pressure
(COP) on the blade (Houdijk, de Koning, de Groot, Bobbert, & van Ingen Schenau, 2000;
van der Kruk, den Braver, Schwab, van der Helm, & Veeger, 2016; Yuki, Ae, & Fujii, 1996).
Dierent from the hinge-opening klapskate in long-track, in short-track skaters have a xed
blade, where the shoe is placed o-centre from the blade. An instrumented skate should
enable a skater to wear her own shoes and ride her own blade.
e purpose of this paper is to perform an analysis of the push-o forces of elite-short-
track speed skaters, to eventually improve the short-track skating performance. First, we
report on an instrumented short-track speed skate; Secondly, a general description of the
force patterns in short-track speed skating in terms of stroke-time, normal and lateral force
level and COP on the blade is given, based on force data of elite speed skaters. irdly, we
explore within-group dierences in a group of elite speed skaters related to their ranking
based on personal records (PR). We hypothesise that, despite the homogeneity of a group
of elite short-trackers, the instrumented skate can determine dierences in push-o tech-
niques within the group.
Method
Data collection
Data were collected on an indoor ice rink in ialf Heerenveen. Twelve (eight male and four
female) Dutch elite short-track skaters participated in the experiment aer signing a written
informed consent, which had been approved by the Del University of Technology Human
Research Ethics Committee. All riders were within the top 70 of the world ranking (WR).
However, two males were excluded from the test, since one fell and one did not perform
according to exercise, and one female was excluded due to failing equipment. All riders were
equipped with an instrumented skate at their right foot which measured the normal and
lateral forces at the skate and the point of application of the force (COP) (Figure 1). Force
measurements were only performed for one side, due to the available means. In consultation
with the national coach, the right side was chosen, it being the most interesting side during
the curve. e skaters were lmed by ve cameras, one at each end of the straight, one at
the inside of each curve and one panning camera at the nish line. e skaters skated ve
rounds at constant velocity. e participants were asked to skate lap times of 9.2s to 9.3s
for the males, and 9.8–9.9 s for the females. Lap times were measured with a transponder
worn by the skaters, using the MyLaps system (MYLAPS Timing Services, Nijmegen, the
Netherlands).

SPORTS BIOMECHANICS 3
e skaters were ranked based on their PR in an XL (an all-out lap when the skater is at
speed) during practice, which was obtained via the national coach. e average PRs and
measured lap times with the corresponding SDs are given in Table 1.
Instrumented short-track skate
e instrumented short-track skate (ISTS) consists of two self-designed cups (mountable
on high-end blades of the brand EVO) (Figure 1). Each cup consists of a sandwich con-
struction that clasps a piezoelectric three-component force sensor (Kistler 9602, Kistler
Group, Winterthur, Switzerland). e output of the sensor is logged on a SD card and sent
over Bluetooth via a data logger (Shimmer3, Ireland). e force sensors are powered by
rechargeable Li-Ion batteries. A digital start–end pulse can be logged, to enable synchro-
nisation with external measurement devices. e weight of the instrumented cups and
electronics is 400g. e instrumented cups replace the normal cups of the skate, so in total
the added weight is 340g (around 25% of the total skate). e height of the instrumented
cups is 18mm (normal height diers among skaters, on average 12mm).
e calibration of the ISTS was performed using a tensile testing machine (Zwick Z100,
Zwick Roell, Ulm, Germany, principal accuracy 1N). e set-up is the same as the one
used in van der Kruk et al., (2016), with the single dierence that not four, but ve posi-
tions (P1-P5) were tested on the blade (applied force up to 2,500N). Calibration in normal
direction resulted in correlations of R2=0.989, with a root-mean-square error (RMS) of
55N (SEM=1N); the correlation for the lateral direction yielded R2=0.993 with the cor-
responding RMS error of 23N (SEM=0.4N). As the force in longitudinal direction (ice
friction) is likely to be lower than 10N (Lozowski, Szilder, & Maw, 2013), which is lower
than the cross-talk of the sensors, this force component is not used.
Data analysis
Push-o forces (force patterns)
e measured forces were divided into separate strokes over the four phases: entering the
curve (EC), hanging into the curve (C), leaving the curve (LC) and entering the straight
Figure 1.The ISTS consists of two self-designed cups (mountable on EVO blades).
The skate measures the forces in the normal (Fn) and lateral (Fl) direction of the blade. The lean angle of the skate (α) distributes
these local forces into the horizontal push-off force (Fh) and the vertical force (Fv). Due to eversion of the foot (β), there can
be a skewed push-off on the skate.

4 E. VAN DER KRUK ET AL.
Table 1.(A, B) M±SD of the PRs and Laptimes, and the average and peak measured normal and lateral forces (normalised to body weight), COP at the blade, and Stroke
Time. For stroke EC, C, and LC five strokes (s=5) per participant were included, for stroke ES three (s=3). (B) males and females separately.
[A] [B]
N=9 (males and females) N=3 (females) N=6 (males)
Avg Peak Avg Peak Avg Peak
PR (s) 8.3±0.22 8.50±0.16 8.1±0.08
Laptimes s(s) 9.49±0.37 9.95±0.19 9.26±0.10
Normal force EC 5 (N/BW) 0.96±0.10 1.66±0.15 1.05±0.12 1.78±0.17 0.92±0.06 1.60±0.10
C 5 (N/BW) 1.40±0.17 1.96±0.16 1.30±0.24 2.01±0.21 1.45±0.14 1.94±0.15
LC 5 (N/BW) 1.02±0.09 1.55±0.16 0.99±0.12 1.56±0.14 1.04±0.08 1.55±0.18
ES 3 (N/BW) 0.88±0.06 1.32±0.10 0.88±0.11 1.38±0.14 0.88±0.03 1.29±0.08
Lateral force EC 5 (N/BW) 0.24±0.08 0.77±0.22 0.32±0.03 1.00±0.14 0.19±0.07 0.66±0.16
C 5 (N/BW) 0.41±0.08 0.74±0.23 0.48±0.06 1.02±0.10 0.37±0.06 0.59±0.09
LC 5 (N/BW) 0.31±0.07 0.75±0.19 0.38 ± 0.05 0.97±0.12 0.27±0.04 0.64±0.08
ES 3 (N/BW) 0.28±0.08 0.66±0.24 0.35±0.05 0.91±0.21 0.24±0.07 0.53±0.12
COP EC 5 (–) 0.45±0.03 0.83±0.14 0.46±0.01 0.91±0.10 0.44±0.03 0.79±0.15
C 5 (–) 0.49±0.03 0.88±0.10 0.50±0.02 0.98±0.02 0.49±0.03 0.83±0.08
LC 5 (–) 0.48±0.03 0.79±0.11 0.48±0.01 0.77±0.09 0.48±0.03 0.80±0.13
ES 3 (–) 0.44±0.04 0.55±0.05 0.44±0.03 0.57±0.07 0.44±0.04 0.54±0.04
Stroke time EC 5 (s) 1.12±0.17 1.22±0.17 1.07±0.15
C 5 (s) 0.99±0.14 0.92±0.09 1.02±0.16
LC 5 (s) 0.61±0.08 0.68±0.09 0.57±0.04
ES 3 (s) 0.65±0.08 0.73±0.05 0.61±0.06

SPORTS BIOMECHANICS 5
(ES). All measured force data were normalised to body weight. e M and SD of the peak
(peak) and average (avg) normal (FN) and lateral forces (FL), the COP on the blade, and
the stroke-time (ST) of nine participants (six males, three females) were determined. Of
each participant ve strokes (s=5) were included for EC, C and LC and three strokes of
ES (s=3), because fewer strokes were available since sometimes a short, corrective stroke
was performed instead of ES. We will refer to this corrective stroke as a transition stroke
(T). Since this stroke is only performed sporadically, we did not include the stroke in the
statistical analysis.
A repeated measures ANOVA (N=9) was performed to compare phases (EC, C, LC,
ES) for the within-participants variables: FN-peak, FN-avg, FL-peak, FL-avg, COPpeak, COPavg, ST;
sex was added as a between-participant factor. Only for the average normal force (FN-avg)
an interaction eect between sex and stroke phases was found, however since the eects
for average normal force within men and women were similar, it is justiable to still take
the groups together and look at the main eect. Pairwise comparison was done with a
Bonferroni post hoc analysis when a main eect was found. Only for stroke time (ST)
sphericity was not met, for which a Greenhouse–Geisser correction was performed. A
signicance level of p<0.05 was employed.
Within-group dierences and PR
To determine the correlation between PR and the average, and peak forces in normal, and
lateral direction, a Pearson test was performed resulting in a pairwise linear correlation
coecient (r). Additionally, the correlation between PR and the average COP on the blade
was tested. ese analyses were performed on the males only (N=6), due to the small sample
size of the female group. From each participant, the peak and average push-o forces were
determined for each measured stroke; the average was taken over the measured strokes to
enter as number in the Pearson test. A signicance level of p<0.05 was employed, p<0.10
was used for comparisons which are close to be signicant.
Results
Instrumented skate
e instrumented skate functioned well during the testing and the signals of the skate were
stable throughout the experiment. Installing and de-installing the instrumented pots on
the skater’s shoe and blade was done on the ice in less than ve minutes by the equipment
manager of the team. In spite of the increased height and weight of the skate, the skaters
felt comfortable riding the skate at high velocities.
Push-o forces
A main eect was found between the dierent phases for the variables FN-peak, FN-avg, FL-avg,
COPpeak, COPavg, and ST (Table 1). Based on the pairwise comparison (Table 2), the four
dierent phases (EC, C, LC, ES) could be distinguished based on the normal and lateral
force level of the push-o forces of the skaters). Figure 2 and Figure 3 show the skating
motion together with the measured normal and lateral forces and COP (averaged over
nine participants).

6 E. VAN DER KRUK ET AL.
Table 2.Repeated measures one-way Anova of the phases EC, C, LC and ES for the nine participants.
Notes: Pairwise comparison of the different motion phases (EC, C, LC, ES) is performed using a Bonferroni post hoc analysis;
x indicates a significant difference (p<0.05).
*sphericity is not met, a Greenhouse–Geisser correction was performed.
N=9
Avg F-test
Mauchly’s
sphericity Bonferroni
EC-C EC-LC EC-ES C-LC C-ES LC-ES
Normal force F(3,21)=81.92,
p < 0.001
χ2(5)=7.66,
p=0.180
x x x x
x
Lateral force F(3,21)=34.47,
p < 0.001
χ2(5)=9.024,
p=0.100
x x x x
COP F(3,21)=16.62,
p < 0.001
χ2(5)=4.002,
p=0.550
x x x
x
Stroke time F(1.35,9.43)=32.77,
p=0.0001
χ2(5)=16.01,
p = 0.010*
x x x x
Peak
Normal Force F(3,21) =68.10,
p < 0.001
χ2(5)=8.099,
p=0.110
x x x x
x
Lateral Force F(3,21)=2.31,
p=0.105
χ2(5)=6.093,
p=0.230
COP F(3,21)=29.60,
p < 0.001
χ2(5)=8.020,
p=0.150
x x x x
Figure 2.Overview of the short-track speed skating motion, measured at constant velocity.
Four strokes were distinguished, which are described in the results. The numbers indicated in the pictures correspond to
the numbers in the graphs. Plotted are the mean measured normal and lateral forces of the six males and three females, the
bandwidth indicates the SD. The strokes are normalised to time. The numbers at the blades indicate the COP at the blade
in that instant of the stroke.

SPORTS BIOMECHANICS 7
e strokes at the start of the curve (EC and C) are signicantly longer than the other
two strokes (ST=1.12s and ST=0.99s respectively). EC, the stroke in which the skater
enters the curve, distinguished itself by the dip in normal force aer the double stance phase
(20–50% of the stroke) (Figure 2). Additionally, stroke EC was characterised by the highest
peak normal forces (1.66N/BW) (together with stroke LC (1.55N/BW)), and the lowest
average lateral force, (0.24N/BW) (together with stroke ES (0.28N/BW), with a mean peak
lateral force of 0.77N/BW.
Stroke C, the stroke where the skater hangs into the curve (see Figure 2) could be sepa-
rated from the other three based on force proles based on the high normal forces (average
1.40N/BW, peak 1.96N/BW) combined with the plateau-like lateral forces (average 0.41N/
BW, peak 0.74N/BW).
e strokes where the skater exits the curve, stroke LC and ES, were signicantly shorter
than the other two (on average 0.61s and 0.65s, respectively). e rst stroke leaving the
curve (stroke LC) was characterised by signicantly higher average and peak normal forces
(1.02N/BW and 1.55N/BW, respectively) than the consecutive stroke, entering the straight
(stroke ES) (0.88N/BW and 1.32N/BW, respectively). e COP of ES diered signicantly
from the other strokes: it shied to the rear of the blade at the end of the motion —resulting
in a peak COP of 0.55—, while in the other strokes, the skater moved to the front of the
blade—resulting in a peak COP of 0.79–0.88.
Figure 3.Plotted are the mean average positions of the COP throughout a stroke of the six males and
three females; of each participant 5 strokes were included in the data.
The bandwidth is the SD. The strokes are normalised to time. The COP at the skate is indicated as a ratio, where 0 is at the
rear of the blade and 1 is at the front of the blade. Remarkable is that in the stroke in which the skater enters the straight
(ES), the COP shifts to the rear of the skate at the end of the stroke.

8 E. VAN DER KRUK ET AL.
e males were able to skate the specied lap time, while the females had a larger var-
iation in maintaining their specied lap time. In Table 1(B), the measured data for males
and females are given separately. e lap times of the females were higher than lap times
of the males, as instructed. Note however that, although there is a large dierence in lap
times between the males and females, there is no dierence in normal forces. e lateral
forces per body weight of the females, however, show a clear trend to be higher compared
to the males. Ranking the lateral forces for all participants shows that the females have the
highest FL-peak for EC, C, and LC, and the highest FL-avg for LC. For the other phases, the
females were in the fourth highest FL-peak and FL-avg.
Correlation between measured force data and PR
e Pearson correlation—performed on the group of males to determine the correlation
between PR and lateral force, normal force, and COP at constant speed—showed signicant
correlations between the COP and PR (Table 3, Figure 4). e average COP in LC and the
peak COP in stroke C have a signicant positive correlation (r=0.86, p=0.030 and r=0.82,
p=0.048, respectively) with PR, indicating that skaters with a better PR keep their COP
more to the rear of their blade when riding and exiting the curve. Also, the average COP in
the curve and while entering the straight appears to show a positive relationship with PR
(r=0.81, p=0.052 and r=0.76, p=0.077 respectively). Additionally, we found a positive
trend (r=0.74, p=0.096) between PR and the peak lateral force in stroke EC, indicating
that skaters with a better PR tend to apply lower lateral forces.
Although skating at similar speeds, the applied normal force levels (FN) diered between
the skaters. Figure 5 shows the most distinct force patterns between male individual speed
skaters. e graphs show diversity between the elite male speed skaters in the executions of
the four strokes, but this diversity could, in this study, not be related to PR with the chosen
measures.
Discussion and implications
e practical usability of the developed ISTS was demonstrated in this experiment. e
four phases (EC, C, LC, ES) in the short-track round could be well distinguished based on
the measured push-o forces. Within the elite speed skaters, we determined dierences in
skating technique and related these to the ranking of the skaters based on PR, which led to
signicant correlations with COP and the lateral forces. is makes the instrumented skate
Table 3.Pearson correlation coefficient between PR and the forces, COP, and ST, of the males (N=6).
*indicates a correlation where p<0.05; **indicates a correlation where p<0.10.
EC C LC ES
Fn Avg 0.72 0.57 −0.01 −0.01
Peak 0.66 0.40 −0.14 0.18
Fl Avg 0.63 0.69 0.73 0.62
Peak 0.74** 0.55 0.48 0.48
COP Avg 0.60 0.81** 0.86* 0.76**
Peak 0.43 0.82* 0.52 0.45
ST Avg −0.62 0.52 0.34 −0.40

SPORTS BIOMECHANICS 9
a useful tool for skaters and coaches during short-track practices. Despite the homogeneity
of the group of elite short-trackers, the instrumented skate was able to determine dierences
in push-o techniques within the group.
Force patterns
e four phases in short-track speed skating can be distinguished with the instrumented
skate based on force level, stroke time and the COP measured with the instrumented skate
for the right side. e phase entering the curve, EC, distinguished itself by the dip in normal
force aer the double stance phase (20–50% of the stroke) (Figure 2). is is caused by the
so-called shue, a motion where the skater changes from the medial (inside) to the lateral
(outside) side of the blade and back. In this motion, skaters move their upper body up and
down, which shis the centre of mass of the skater, hence the dip in the normal force. Due
to this shue, there is also a negative lateral force at the start of the stroke and the COP at
the blade shis from front to rear and back again. Stroke EC is also the only stroke where
the skaters do not perform a cross-over with the le leg.
e force data of stroke C, where the skater leans into the curve, are most distinguishable
from the other three by the high normal forces. e level of the normal force is here directly
related to the centrifugal forces acting on the skater in the curve; these increase with an
increased velocity. e decrease in normal force—just before the peak at the end of the
stroke—is caused by the le (repositioning) leg in the air; this le leg is pulled to the front,
Figure 4.Scatterplot for the trends and correlations between PR and the normalised lateral forces, and
COP position on the blade for the male participants (N=6).

10 E. VAN DER KRUK ET AL.
thereby drawing it underneath the right leg, shiing the COM (Figure 2). is shiing in
COM is what induces the decrease in the measured forces.
e COP of ES diers signicantly from the other strokes: it shis to the rear of the
blade at the end of the motion, while in the other strokes, the skater moves to the front of
the blade. is is caused by the fact that ES is a transitional stroke from the curve to the
straight. e skater comes back upright, so most correction and steering is done here, which
is linked to the COP on the blade.
In this study, only the forces on the right skate were measured. e comparison of average
normal forces between skaters should therefore be interpreted with care, since the force
on the le skate—during double stance, when both skates are on the ice—inuences this
force level. For a complete picture, it would therefore be benecial to measure the push-o
forces of both skates synchronously, also because, based on the knowledge of long-track
speed skating, dierent force patterns are expected between le and right, especially for
the forces in the curve (van der Kruk et al., 2016).
COP and lateral forces on the blade
Results show that the male skaters with a better PR kept the COP more to the rear of their
blades while leaning into (C) and leaving (LC) the curve, and entering the straight (ES).
Additionally, we found that skaters with a better PR, showed lower lateral peak forces while
Figure 5.Most distinctive patterns between individual male skaters based on their normal force patterns.
The shaded areas reflect one SD. The ranking of the skaters is indicating with R# (ranking 1–6, based on PR). The differences
in normal force levels (FN-avg, FN-peak) between the skaters were not related to PR ranking. They probably have their origin in
the efficiency of the skating motion.

SPORTS BIOMECHANICS 11
entering the straight. Although these results are based on a small sample size of elite speed
skaters (n=6), and may therefore not be as robust, it does seem to indicate that the handling
of the skate is an important factor for short-track performance. We refer to handling as the
actions to steer the skate. We expect that the skaters use the shiing of COP on the blade to
steer, but also the lateral forces on the skate can be an intended action to induce a moment
on the cups and thereby bending the blade, which will cause the skate to steer as well. e
length and the stiness of the blade then determine the necessary absolute lateral force level
to bend it. Since the men and women skate on the same blade, and therefore likely need to
apply the same absolute lateral forces, this might explain the fact that we found signicant
higher lateral forces when we corrected for body weight for the women.
Although not investigated yet, we hypothesise that this lateral force is, apart from the
active steering control action of the skater, partly a result of an involuntary skewed push-
o, due to a lack of active control to stabilise the knee and ankle. Felser et al. (2016) already
found that the right ankle eversion’s isometric and concentric maximum voluntary torque
were signicantly correlated to performance in short-track speed skating. A previous study
in long-track speed skating already argued that a lateral force—in the frame of the skate—
does not directly contribute to the forward velocity (performance) of the skater (van der
Kruk, van der Helm, Schwab, & Veeger, 2016). erefore, from a mechanical point of view,
the lateral force should be minimised if it does not serve the purpose of steering the skate.
Hence, the relation between active control to stabilise the knee and ankle and lateral force
on the ice is a topic well worth looking into. Especially, since the female short-track skaters
showed a trend of applying higher lateral forces per body weight than their male colleagues,
while they skated on a—imposed—lower velocity.
Force level and performance
Although all male participants skated at the same velocities, and the four general stroke
patterns could be distinguished, we do see diversity between elite male speed skaters in the
executions of the four strokes. e normal force levels (FN) diered between skaters at the
same speed (Figure 5), but were not related to their ranking in PR. Since the skaters skated
at the same velocities, dierences in normal force levels seem to point at a dierence in e-
ciency. Also, the fact that the female participants skated at lower velocities than the men, but
did not apply lower normal forces (corrected to body weight), hangs towards an eciency
measure. To gain insight into this eect, data of individual skaters at dierent velocities
and preferably some full-out exercises would be necessary. Also, measuring the velocity of
separate strokes would be helpful. Expanding the number of participants would not only
be hard—because the study is focused on top-level athletes—, but also doubtful whether
it would benet the results. It would certainly increase the robustness, but also decrease
the sensitivity of an already homogeneous data-set with small margins. In the future, the
instrumented skate and push-o force proles can be used to determine the eciency of
elite short-track skaters and help to give training advice whether the skater should focus
on improving strength or technique.

12 E. VAN DER KRUK ET AL.
Conclusion
A wireless force measuring instrumented short-track speed skate was constructed and cal-
ibrated on a tensile testing machine (accurate up to 2.2% in normal direction and 1.4% in
lateral direction), which could be used in routine training. Within the homogeneous group
of male elite speed skaters, diversity of execution of the force patterns in the four phases of
skating is evident, while skating at the same velocities. Higher ranked male skaters show
a trend to have a COP more to the rear of the blade, and lower lateral forces for several
phases. Females showed a trend towards applying higher body weight normalised lateral
forces than the males, while skating at imposed lower velocities.
Acknowledgments
e authors gratefully acknowledge ir. Jorine Koopman of the Hague University and the students
of the Hague University and Del University of Technology that contributed to the design of the
instrumented skate. We acknowledge Sjinkie Knegt for the manual fabrication of the custom cups.
We thank dr. ir. J.C.F. de Winter for his advice on statistics. Furthermore, we want to acknowledge the
national coach Jeroen Otter and assistant coach Kip Carpenter for their endless ideas and curiosity.
And nally, the national Dutch speed skating selection for participating in this research.
Disclosure statement
No potential conict of interest was reported by the authors.
Funding
is work was supported by NWO-STW [grant number 12870].
ORCID
DirkJan (H) E. J. Veeger http://orcid.org/0000-0003-0292-6520
References
Felser, S., Behrens, M., Fischer, S., Heise, S., Bäumler, M., Salomon, R., & Bruhn, S. (2016).
Relationship between strength qualities and short track speed skating performance in young
athletes. Scandinavian Journal of Medicine and Science in Sports, 26, 165–171. doi:10.1111/
sms.2016.26.issue-2.
Houdijk, H., de Koning, J. J., de Groot, G., Bobbert, M. F., & van Ingen Schenau, G. J. (2000). Push-
o mechanics in speed skating with conventional skates and klapskates. Medicine and Science in
Sports and Exercise, 32, 635–641. doi:10.1097/00005768-200003000-00013.
Lozowski, E., Szilder, K., & Maw, S. (2013). A model of ice friction for a speed skate blade. Sports
Engineering, 16, 239–253. doi:10.1007/s12283-013-0141-z.
van der Kruk, E., den Braver, O., Schwab, A. L., van der Helm, F. C. T., & Veeger, H. E. J. (2016).
Wireless instrumented klapskates for long-track speed skating. Sports Engineering, 19, 273–281.
doi:10.1007/s12283-016-0208-8.
van der Kruk, E., van der Helm, F. C. T., Schwab, A. L., & Veeger, H. E. J. (2016, July). Giving the
force direction: Analaysis of speed skater push-o forces with respect to an inertial coordinate
system. Proceedings of the 34rd International Conference of Biomechanics in Sports (pp. 112–115).
Tsukuba, Japan: ISBS
Yuki, M., Ae, M., & Fujii, N. (1996). ド ケ ト の ド反 [Blade reaction forces in speed skating]. Society of
Biomechanisms Japan (SOBIM), 13, 41–51.