Biomechanics and Medicine in Swimming XI

Relationship between Eggbeater Kick and Support
Scull Skills, and Isokinetic Peak Torque
homma, M. 1
1 University of Tsukuba, Tsukuba, Japan
Eggbeater kick and support scull are essential basic propulsive techniques
in synchronized swimming. The aim of the present study was to
ascertain the relationship between muscle strength, and eggbeater kick
skills and vertical position support skills in elite synchronized swimmers.
The isokinetic peak torque of legs, trunk and shoulders were measured
using the BIODEX System 3. From the findings in this study, to improve
eggbeater kick skills, the importance of strengthening the muscles
associated with hip flexion such as the hamstrings, rectus abdominis,
and psoas major was suggested. To improve the support scull skills, upper
arm abductors such as the infraspinatus and teres minor should be
trained and the muscles around the scapula should be strengthened in
proper balance.
Key words: propulsive techniques, muscle strength, synchronized
swimming
IntroductIon
The eggbeater kick (Figure 1) is a rotational movement of the lower legs
in which a swimmer opens the legs sideways with the hip joint flexed
and bends the knees while swivelling both feet in opposing circles. The
load above the water surface is at least 13 kg when both arms are raised
using this kick (Homma, 2000). Thus, strength to control the body,
hip and leg muscles is needed to elevate the body during synchronized
swimming routines. Support scull is a rotational movement of the forearms
in which a swimmer bends the elbows and sculls the water using
the forearms via internal and external shoulder rotations (Homma and
Homma, 2006). About 14 - 15 kg of load is applied at the maximum
height above the water surface to support a vertical posture (Figure 2),
which is the basic position in synchronized swimming (Homma, 2000).
Thus, the body can only be kept elevated by sculling. Support scull is an
unusual movement in which the forearms are supinated while the shoulders
are externally rotated, and the muscles involved with internal and
external shoulder rotation are thought to be involved. Stress fractures of
the ulna mostly, due to sculling, have been reported in junior synchronized
swimmers (Nagano and Ohata, 1982).
A previous study of the relationship between eggbeater kick skills
and leg muscle strength and between the cross-sectional area of the
thigh and abdominal muscles for elite synchronized swimmers found a
correlation with the isokinetic peak torque, but not the cross-sectional
area of the legs (Homma and Kuno, 2001). The isokinetic peak torque
for knee flexion/extension, internal/external shoulder rotation and hip
abduction/adduction was measured in the study, and a significant correlation
was seen between moderate-speed hip abduction and knee flexion.
This finding suggested that the eggbeater kick can be reinforced
by strengthening the hamstrings, sartorius, gluteus medius and gluteus
minimus by training at moderate speed.
The aim of the present study was to ascertain the relationship between
eggbeater kick skills (technical ability of eggbeater kick) and the
leg and trunk muscle strength, and the relationship between vertical position
support skills (technical ability for supporting vertical position)
and muscle strength of internal and external shoulder rotation.
Methods
Ten female synchronized swimmers (average height, body mass and age,
1.64 ± 0.04 m, 54.5 ± 2.8 kg, 23.8 ± 1.9 yrs, respectively), silver-medallists
at the 2007 World Championships, who were all candidates for the
2008 Beijing Olympic Games, participated in the study.
chaPter2.Biomechanics
Figure 1. Raising the arms out of the water using the eggbeater kick.
Figure 2. Vertical position using support scull.
Eggbeater kick skills and vertical position support skills were assessed
based on their respective test scores obtained during the first qualifying
trial for the 2008 Beijing Olympics in September 2007 (Qualifying
Trial) and the skill evaluation test for Beijing Olympic candidates in
June 2007 (Skill Evaluation Test).
Eggbeater kick skills were assessed based on the two scores: 1) eggbeater
kick (EB) score and 2) height score. International judges and
national coaches determined scores of up to 5 points in half-point increments.
EB score obtained as one of the routine set of tests conducted
during the Qualifying Trial. The routine set comprised five features
that are essential for performing a routine and included propulsive
techniques and figures. During the assessment of eggbeater kick skills,
swimmers were required to raise both arms and move forward while
counting to 12. Swimmers were assessed based on height, stability and
smoothness. Height score obtained as part of the Skill Evaluation Test.
Swimmers moved forward 5 m while sculling in the water without rais-
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