Biomechanics and Medicine in Swimming XI

Ankle
Figure 2. Diagram 0.5 of the robot’s kinematics
chaPter2.Biomechanics
-0.5
0 20 40 60 80 100
results
Kick amplitudes did 0.3not
appeared as a significant parameter (p>0.05). 0.3 0.6
0
However, snorkelling kicks substantially differed in frequency and
depth. Snorkelling frequency was lower than the two others practices
(Table1). This last 0.1 result agrees with measurement made with different
0.1 0.2
0
0
snorkel fins by Zamparo 0 et al. (2006). The kick depth, defined as the
higher position of ankle during a cycle, showed snorkelling depths closer
to the water surface -0.1 than swimming and body-board values.
0
-0.1 -0.2
-0
-0
Table 1. Main ankle kinematic parameters for the three practices: frequency,
amplitude,
-0.3
and depth of swimming kicks.
-0.3 -0.6
-0
Frequency Amplitude Depth
Swimming
-0.5 (Hz)
1.01 0 ± 0.1720 (m)
0.42 40± 0.02
(m)
60 -0.16 80 ± 0.08 100
-0.5-1
0 20 40 60 80 100
-1
Snorkelling
Body-board
0.85 ± 0.19
0.98 ± 0.18
0.36 ± 0.02
0.42 ± Knee 0.02
0.02 ± 0.26
data1
-0.08 ± 0.08
Body-board
Ankle
Swimming data1
Hip
Snork Bod
1
Concerning the inverse dynamics results, torques values gradually in-
0.5 1.5
creased from the ankle to the hip joint. For all joints, the highest amplitude
was found around 0.6 the flexion/extension axis.
0.3
1
0
The robot reproduces seven stock swimming cycles with a standard
deviation lower than 4%. On the ankle joint, amplitude patterns are
lower for body-board. 0.2In
knee and hip torque amplitudes, no difference
0.5
0.1
0
were found between the three activities. Forces and torques patterns
measured on the ankle sensor of the robot showed only one oscillation.
The torque pattern -0.2 computed by the model described a double oscillation
during stroke cycle, both in the knee and the hip (Figure 3). In the
0
-0.1
-0.5
-0
knee joint, during the snorkelling activity, the second upper peak disap-
-0.6
peared, because value of this peak staid negative while the two others
were positive, as well as in the second lower peak for body-board activity
-0.3
-1
-0
80
on knee. In the hip joint, the oscillations were synchronous but snorkel-
-1
ling 100amplitudes were lower 0 than 20 others. 40 60 80 100
-0.5 -1.5
0 20 40 60 80 100
data1 Body-board Swimming
Figure 3. Evolution of tri-dimensional joint torques for body-board,
snorkelling Snorkeling and swimming activities.
data1 Bod
Flexion / Extension
Flexion / Extension
Flexion / Extension
Flexion / Extension
0.5
0.3
0.1
0
-0.1
-0.3
0.51
Ankle
Ankle Knee
51
0
0
-0
-0
data1 Bod
1