Biomechanics and Medicine in Swimming XI

dIscussIon
The results of the present study confirmed a relationship between eggbeater
kick skills and the isokinetic peak torque for 60 or 180˚/s (left)
knee flexion or 60˚/s trunk flexion. Homma and Homma (2005) suggested
that when teaching the eggbeater kick, it is important to elevate
the knees above the greater trochanter and elevate the heels near the
gluteal region. Executing the kick is thought to involve low- and moderate-speed
and low-speed hip and knee flexion, respectively, suggesting
the importance of strengthening the muscles associated with hip
flexion such as the hamstrings, rectus abdominis, and psoas major. This
finding supported the previous study for elite synchronized swimmers
(Homma and Kuno, 2001) that strengthening the hamstrings, sartorius,
gluteus medius and gluteus minimus by training at moderate speed can
reinforce the eggbeater kick. On the other hand, hip abduction was not
measured in the present study due to technical limitation of analyzer.
Therefore, hip abduction could not be compared with previous findings
(Homma and Kuno, 2001), but knee flexion was comparable, suggesting
a close correlation between eggbeater kick skills and left knee flexion.
Furthermore, the present study identified a correlation with low-speed
trunk flexion, suggesting the importance of strengthening the rectus abdominis,
obliquus internus abdominis, psoas major and rectus femoris
that bend the trunk, by training at low speed.
The significant relationship between external shoulder rotation and
vertical position support skills might have been due to the specificity of
support scull movements. The support scull is a rotational movement of
the forearms with bent elbows, and it is an unusual movement where
a swimmer bends the elbows and externally rotates the shoulder while
supinating the forearms with the palms facing the face (Homma and
Homma, 2006). Internal shoulder rotation is occasionally used during
routine activities, whereas external shoulder rotation is rare. Therefore,
rather than individual differences in internal rotation, those in external
rotation are closely related to support scull skills. Therefore, upper arm
abductors such as the infraspinatus and teres minor should be trained.
These muscles are called inner muscles, and since they are in the deep
layers of the shoulder, athletes are not often aware of them. Unlike
outer muscles, training inner muscles is more difficult and should be
performed using rubber bands and light-weight dumbbells, with careful
monitoring of muscle movement. Also, large muscles that connect
the trunk and upper arms such as the pectoralis major and latissimus
dorsi are important when sculling with fixed shoulders. Therefore, to
improve support scull skills, the muscles around the scapula should be
strengthened in proper balance. Although we reached these implications
in the present study, how the muscles contribute to the eggbeater kick
or sculling movements should be analyzed with EMG in future studies.
Since eggbeater kick and sculling movements are symmetry, there were
no significant differences between right and left peak torques. However,
for only one side, some significant correlations between peak torques
and scores were obtained, therefore, dominance assessment is needed
in a future.
The BIODEX was used in the present study to measure the isokinetic
peak torque of single joint movements. As they differ from the
natural output characteristics for synchronized swimming, a method
of quantifying the muscle strength and power required for floating using
the support scull and eggbeater kick is required. However, periodic
checking of the muscle strength of synchronized swimmers using a
muscle function analyzer is useful for training purposes, and continued
use of the system as a control test is warranted.
reFerences
Homma, M. (2000). Load above the water surface during the movements
in synchronized swimming. Bulletin of sports methodology, University
of Tsukuba, 16, 13-22.
Homma, M. & Homma, M. (2005). Coaching points for the technique
of the eggbeater kick in synchronized swimming based on three-
chaPter2.Biomechanics
dimensional motion analysis. Sports Biomechanics, 4(1), 73-88.
Homma, M. & Homma, M. (2006). Support scull techniques of elite
synchronised swimmers. Biomechanics and Medicine in Swimming X,
220-223.
Homma, M. & Kuno, S. (2001). Relationship between eggbeater kick
skills and isokinetic peak torque and muscle cross-sectional area in
elite synchronized swimmers. Japanese Journal of Physical Fitness and
Sports Medicine, 50(6), 929.
Nagano, T. & Ohata, N. (1982). Stress fracture of the ulna in a synchronized
swimmer. East-Japanese Journal of Sports Medicine.
AcKnoWledGeMents
I would like to thank the project research, Institute of Sport and Health
Sciences in University of Tsukuba for a grant that made it possible to
complete this study.
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