Biomechanics and Medicine in Swimming XI

y a video mixer. The image taken from above the swimmer was inserted
mixer image using 4 image dividers.
RESULTS and DISCUSSION
Figure 3 shows the composite underwater and overwater image of the swimming
motion obtained by the observation equipment. The picture appears as if the swimmer
chaPter2.Biomechanics
had been observed in a water tank through a window. Figure 3 also shows the threedimensional
accelerations and the angular velocity obtained by the data logger attached
on the forearm synchronized with the motion image. In the case of the breaststroke
Fig. 1 Data logger of motion sensors
Fig.1 Data logger of motion sensors
Figure 1 shows a data logger of motion sensors which has 3
accelerometer components, 3 gyroscopic components, a depth
ws a data sensor logger and a of propeller motion system sensors speedometer which built-in has (PD3G3Gy 3 accelerometer components,
components, made by a Leonard depth Little sensor company). and It has a a propeller cylindrical shape system of speedometer built-in
diameter φ 23mm and length of 235mm and is composed of
ade by Leonard a CPU, 256MB Little memory, company). and 8 A/D converter It has a components. cylindrical shape of diameter φ
ngth of 235mm The data logger and can is measure composed 8 hours continuously of a CPU, in 128Hz. 256MB memory, and 8 A/D
The data logger was set on the backside of the left forearm on a
mponents. three-dimensional The data coordinate logger axis can as shown measure in Fig.2. 8 Data hours were continuously Fig.3-5,6,7 respectively. in 128Hz.
sampled at 128Hzd, that is, almost 500000 datum in one hour.
ger was set on the backside of the left forearm on a three-dimensional
The three-dimensional acceleration and the angular velocity data
is as shown taken in from Fig.2. the data Data logger were and corresponding sampled to at swimming 128Hzd, that is, almost 500000
movements, were extracted with Igor ProVer.6 of the Wavemet-
e hour. The three-dimensional acceleration and the angular velocity data
ric Co. Ltd. These wave data were synchronized with the swim-
151
e data logger Biomechanics ming motion and images corresponding and Medicine by Pixel Runner XI to of Tellus Chapter swimming Image 2 Biomechanics
Co. Ltd. movements, were extracted
by matching the motion image with the arm entering the water
oVer.6 of and the the peak Wavemetric point of the data Co. waves. Ltd. These wave data style. were synchronized
imming motion images by Pixel Runner of Tellus Image Co. Ltd. by
Time A
motion image with the arm entering the water and the peak point of the
y direction
[m/s 2 ]] 1. Arm Side Slide
[m/s 2 ]] 2. Arm Extension
[m/s 2 ]] 3. Arm Pull
[m]] 4. Depth
[deg/s] 5. Arm Pitch
[deg/s] 6. Arm Roll
[deg/s] 7. Arm Yaw
152
Fig.3 Biomechanics Chronological and Medicine 3D XI acceleration, Chapter 2 Biomechanics 3D gyro and depth data of arm
stroke synchronized with whole body image of under and over water
shown in Fig. 3, a sequence of opening and closing motion of the arms appeared in Arm
Slide in Fig. 3-1. Concerning the acceleration of Arm Extension in Fig.3-2, two peaks
were seen in each stroke, although the motion of the arm itself was carried out
smoothly. Since the accelerometer has also gathered gravitational acceleration, the
Extension negative peak in was Fig.3-2, obtained two when peaks the arm were was seen moving in each downward. stroke, The although effect of the
motion gravitational of the acceleration arm itself was was seen as carried well in out the acceleration smoothly. of Since Arm Pull the in accelerom-
Fig.3-3.
The complex 3 component angular velocity of arm Pitch, Roll, and Yaw is shown in
eter has also gathered gravitational acceleration, the negative peak was
In order to understand these data better, synchronizing this motion image and the
obtained when the arm was moving downward. The effect of gravita-
data waves was a very effective mean to grasp the differences in details of an individual
tional swimmer's acceleration strokes even was in the seen same swimming as well in style. the acceleration of Arm Pull in
The graph at the top of Fig. 4 shows the transition of flexion/extension motion of
Fig.3-3. the forearm The described complex with 3 angular component velocity. angular The graph velocity in the middle of arm indicates Pitch, the Roll,
and wavelet Yaw transformation is shown in for Fig.3-5,6,7 the same data respectively.
and the graph at the bottom shows the
transition of depth. Each of them was acquired with the sensor attached on the forearm
In in order the freestyle to understand stroke. Comparing these the data graphs better, at the synchronizing top and the bottom, this the motion angular image
velocity and the in the data stroke waves phase was is a almost very constant, effective while mean that to in grasp the recovery the differences phase
decreased rapidly. The Fourier transformation converts a spectrum space of a certain
in period details into of a frequency an individual space. On swimmer’s the other hand, strokes the wavelet even transformation in the same is swimming
the time
series data of the momentary frequency conversion in the same time space. In other
recovery phase
acceleration:
Arm extention
i i ll x direction
acceleration:
SliceSectionC\
Arm side slide
stroke/pull phase
i i
z direction
Fig. 4. Gyro sensor data of x-direction, wavelet transform for the
acceleration:
Arm pull
i i
Fig. 2 Definition of 3-coomponents on data logger
Fig.2 Definition of 3-components on data logger
Regarding the logger signal processing, the wavelet transformation was
analyzed by using free macro software of Ethographer (Sakamoto et al.,
same wave and transition of depth acquired with the sensor attached
on the forearm in the freestyle stroke.
2009) on Igor Pro. Wavelet transformation is one of the techniques of
Regarding the chronological the frequency logger signal analysis. The processing, Morlet function the of wavelet 15 cycles
Biomechanics Fig. 5(a) and Section Medicine of TimeA XI Fig. 5(b) Chapter Section of 2 Time Biomechanics
B
transformation Figs. 5. was Time sliced analyzed section data by of wavelet transform output, Fig.4 at
using was employed free macro as the software mother wavelet of Ethographer in this study. A (Sakamoto key advantage
time A and B shown in Fig.4. The sliced section shows momentary
et al., 2009) cycle on (=1/frequency) Igor Pro. analysis. Wavelet
over Fourier transformation is temporal resolution. In addition, wavelet
transformation is one of the techniques of the chronological frequency analysis. The
transformation captures both frequency and location information.
Morlet function of 15 cycles was employed as the mother wavelet in this study. A key
advantage results and over dIscussIon Fourier transformation is temporal resolution. In addition, wavelet
transformation Figure 3 shows the captures composite both underwater frequency and overwater and location image of the information.
swimming motion obtained by the observation equipment. The picture
RESULTS appears as if the and swimmer DISCUSSION had been observed in a water tank through
a window. Figure 3 also shows the three-dimensional accelerations and
Figure 3 shows the composite underwater and overwater image of the swimming
the angular velocity obtained by the data logger attached on the forearm
motion synchronized obtained with the by motion the observation image. In the case equipment. of the breaststroke The picture appears as if the swimmer
had shown been in Fig. observed 3, a sequence in of a opening water and tank closing through motion a of window. the arms Figure 3 also shows the threedimensional
appeared in Arm accelerations Slide in Fig. 3-1. and Concerning the angular the acceleration velocity of Arm obtained by the data logger attached
on the forearm synchronized with the motion image. In the Fig. case 6. Cycle of the sliced breaststroke section data of wavelet transform output, Fig.4
at sliced section, Cycle 2.2 sec. This is a stroke cycle of freestroke
in this case. The bottom peak shows the turn phase.
103
Time B