a
b
c
CG
a：Elbow joint angle
b：Shoulder joint angle
c：Hip joint angle
CG：Body center of gravity
Strategies for Improving Japanese Elite Male Cross-country Skiers'
Double Poling Skills to an Internationally Competitive Level
Junichi Igawa
1
, Shintaro Kanno
2
, Tsukasa Suzuki
2
and Fumio Mizuochi
3
1
Graduate School of Literature and Social Sciences, Nihon University, Tokyo, Japan
2
School of Dentistry at Matsudo, Nihon University, Chiba, Japan
3
College of Humanities and Sciences, Nihon University, Tokyo, Japan
1 OBJECTIVES
The strategies of raising the cycle rate of the pole
ground contact phase and of overcoming the trade-
off between cycle rate and cycle length have been
noted as important for improving a cross-country
skier's double poling skills (Yoshimoto and Suzuki,
2013).
The present study investigates the problem of
improving the double poling skills of Japanese elite
male cross-country skiers to an internationally
competitive level by analyzing the trade-off or
absence thereof and the timing skills seen in their
gliding motion.
2 METHODS
2.1 Experimental Participants
Fourteen elite male Japanese skiers participated in
this experiment. They were classified into a high-
rank group of six skiers whose gliding velocity in a
set measurement zone was faster than the mean of
all of the skiers, and a low-rank group of eight skiers
whose gliding velocity was slower than the mean.
Male skier A with the fastest gliding velocity was
extracted, and the high-rank group, low-rank group,
and male A were compared with each other.
2.2 Experimental Task
This was full-power gliding in double poling on a
straight, 8-m ascending (5% incline) course. Two
high-speed cameras (300 f/s) were set up in front of
and beside the subjects, and recorded their double
poling gliding motions.
2.3 Measurement Items
Motion analysis software (Frame-DIAS IV, made by
DKH) was used to find three-dimensional coordinate
values of different parts of the body by direct linear
transformation (DLT) from the resulting video. Part
of one cycle of their gliding motion, from the ground
contact of the poles to take-off from the ground, was
understood to be the poling phase (Phase P), and the
part from take-off from the ground to the next
ground contact was understood to be the gliding
phase (Phase G) (see fig. 1 for measurement items
and definitions of angles).
Figure 1: Different measurement items, and definitions of
angles.
2.4 Analytical Methods
We ran a correlation analysis on the relationships
between cycle rate and cycle length in the Phase P
and Phase G of the high-rank group and the low-
rank group. Means of each of the measurement items
for the two groups were tested by unpaired t-test.
The significance level was set to less than 10%.
Gliding in the Phase P of all skiers was the
subject of a hierarchical cluster analysis by the
nearest-neighbour method, with speed, cycle rate,
and cycle length as variables.
①：Time points for maximum flexion angular velocity of the elbow joint to time point maximum flexion angular velocity of hip joint
②：Time points for extension start point of the elbow joint to time point maximum flexion angular velocity of shoulder joint
③：Time points for maximum extension angular velocity of the elbow joint to time points to maximum extension angular velocity of hip joint
7.5
7.0
6.5
6.0
5.5
800
400
-400
-800
0
0.0 0.2
0.4 0.6
0.8 s
Maximum velocity
Minimum velocity
②
①
③
Maximum
flexion
angular
velocity
of the
hip joint
Maximum flexion angular velocity of the
elbow joint
Maximum flexion angular velocity
of the shoulder joint
Maximum
Extension
angular velocity
of the elbow joint
Maximum
extension
angular
velocity of
the hip joint
Velocity of CG（m/s）
Angular velocity of elbow joint （deg/s）
Angular velocity of hip joint （deg/s）
Angular velocity of Shoulder joint （deg/s）
Phase P
Phase G
Mean velocity
Igawa, J., Kanno, S., Suzuki, T. and Mizuochi, F..
Strategies for Improving Japanese Elite Male Cross-country Skiers’ Double Poling Skills to an Internationally Competitive Level.
Copyright
c
 2015 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved

3 RESULTS
The mean gliding speed was 6.69 m/s for the high-
rank group and 6.20 m/s for the low-rank group. The
difference between the highest speed of gliding seen
in the Phase P and the lowest speed of gliding seen
in the Phase G did not show a significant difference
between the high-rank group and the low-rank group.
Of the experimental participants, male A had the
highest gliding speed (one stroke: 7.12 m/s; Phase P:
7.29 m/s; Phase G: 7.01 m/s).
3.1 Relationship between Cycle Length
and Cycle Rate
Table 1: Correlation between cycle length and cycle rate
in the high-rank group and low-rank group. (Pearson
correlation coefficient).
A significant negative correlation was observed
in the relationship between cycle length and cycle
rate, excluding the Phase P of the high-rank group.
Of all the skiers, male A had the fastest Phase P
cycle rate as well as the longest stride. Results from
the cluster analysis allowed us to aggregate and
classify the other skiers' relationships between cycle
rate and cycle length in the Phase P. There seems to
be a tendency for male A to overcome the trade-off
of cycle length and cycle rate. Other high-rank-
group skiers overcame the Phase G trade-off, and
low-rank-group skiers overcame the Phase P and
Phase G trade-offs, a fact which is regarded as a
challenge for improving their double poling skills to
an internationally competitive level.
3.2 Angular Velocity Changes of the
Upper Limb Joints, and the Time
Relationship between Elbow Joint
Extension and Shoulder Joint
Flexion
Maximum flexion angular velocity of the shoulder
joint relative to the elbow joint extension start point
was high in the high-rank group, but low in the low-
rank group, and the difference between the two
groups showed a significant (p=.069). Both time
points coincided for male A (fig. 2 ➀).
Figure 2: In phase P time relationship of elbow joint and
shoulder joint motion and male A's angular velocity
changes.
In the time from the Nagano Olympics (1998) to
the Turin Olympics (2006), skiers at an
internationally competitive level have had
coinciding time points for maximum flexion angular
velocity of the shoulder joint and elbow joint
(Suzuki et al., 2002). However, currently the time
point for the maximum flexion angular velocity of
the elbow joint has moved forward relative to the
maximum flexion angular velocity of the shoulder
joint, appearing at about the same time as ground
contact of the poles, as is the case with male A (fig.
2 ➁). This means that the timing skill where by the
elbow joint flexes at the greatest speed is now earlier
than before.
3.3 Each Joint Flexion Angular
Velocity Changes, and Time
Relationship between Elbow Joint
Flexion and Hip Joint Flexion
Figure 3: In phase P elbow/hip/shoulder joint maximum
flexion angular velocity.
The maximum flexion angular velocity of the
elbow was significantly higher in the high-rank
group than the low-rank group (p=.007). Male A's
angular velocity was substantially the same as the
mean of the low-rank group. The high-rank group
had a slightly higher maximum flexion angular
Phase P Phase G
High rank group -.784 -.907*
Low rank group -.979** -.989**
**:p <.01 *:p <.05
Cy cle rate
Cycle length
-0.029
0.073
-0.003
-0.22 -0.11 0.00 0.11 0.22
Time (s)
Male A
Low rank group
High rank group
†:p<.10
Time points for extension start point of the elbow joint
Angular velocity of Shoulder joint （deg/s）
Angular velocity of elbow joint （deg/s）
7.5
7.0
6.5
6.0
5.5
800
400
-400
-800
0
0.0 0.2
0.4 0.6
0.8 s
②
①
Velocity of CG（m/s）
Male A
0
100
200
300
400
500
600
700
Elbow joint Hip joint Shoulder joint
Angular velocity (deg/s)
High rank group Low rank group Male A
**:p<.01 †:p<.10
†
**

velocity of the shoulder than the low-rank group,
and a significant was noted (p=.080). Male A was
higher than the mean of the high-rank group.
Figure 4: In phase P time relationship between elbow joint
and hip joint motion and male A's angular velocity
changes.
The time point of maximum flexion angular
velocity of the hip, relative to the time point of
maximum flexion angular velocity of the elbow,
appeared late in the high-rank group but came earlier
in the low-rank group, and a significant difference
was observed between the means of the two groups
(p=.029). Both time points coincided for male A,
and were simultaneous with ground contact of the
poles (fig. 4 ➀).
3.4 Joint Extension Angular Velocity,
and Time Relationship between
Elbow Joint Extension and Hip
Joint Extension
Figure 5: In phase G elbow/hip maximum extension
angular velocity and time relationship between elbow joint
and hip joint motion.
The maximum extension angular velocity of the
elbow and hip joints and the time from maximum
extension angular velocity of the elbow to maximum
extension angular velocity of the hip showed no
difference among the three classifications.
4 DISCUSSION
Male A, whose gliding speed in a one-stroke interval
was the highest of the high-rank group, exhibited the
following characteristics.
Male A's high gliding speed is believed to have
been supported not only by the high muscle power
(maximum angular velocity) exerted in elbow and
hip flexion and extension, but also by the timing
skills observed in elbow and hip flexion and in
shoulder flexion and elbow extension in the Phase P.
Shoulder flexion is reflective of muscle power
for pushing the poles to the rear, and it is the final
phase of the kinetic chain for which each part of the
body is responsible in double poling. The timing
skills involved in this kinetic chain are believed to
contribute to an increase in the muscle power for
continuing to push the poles to the rear in double
poling.
These results suggest that improving the Phase P
timing skills to be similar to male A could enable
skiers with particularly high muscle power to
improve their Phase P cycle rate, overcome the
trade-off between cycle length and cycle rate, and
raise their gliding speed.
However, the present study failed to yield clues
as to overcoming the trade-off between cycle length
and cycle rate in the Phase G. In the future,
investigation will need to include data on skiers of a
high internationally competitive level, as indicators.
REFERENCES
Suzuki, T., et al. 2002. Feedback from a Video Motion
Analysis of Cross-country Skier’s Movement. Bulletin
of Education and Research Nihon University School of
Dentistry at Matsudo 2002, Japan.
Yoshimoto, D., and Suzuki, T., Strategy to Increase The
Double-Poling Skill of Women Cross Country Skiers
to an International Level. 6th
International Congress
on Science and Skiing 2013 Book of Abstracts, 125. St.
Christoph a.
0.025
-0.015
0.00
-0.08 -0.04 0.00 0.04 0.08
Time (s)
Male A
Low rank
group
High rank
group
*:p<.05
Time points for maximum flexion angular velocity of the elbow joint
7.5
7.0
6.5
6.0
5.5
800
400
-400
-800
0
0.0 0.2
0.4 0.6
0.8 s
①
Angular
velocity
of hip joint （deg/s）
Velocity of CG（m/s）
Male A
Angular velocity of elbow joint （deg/s）
0.197
0.202
0.183
-0.40 -0.20 0.00 0.20 0.40
Time (s)
Male A
Low rank
group
High rank
group
Time points for maximum extention angular
velocity of elbow joint