Biomechanics and Medicine in Swimming XI

BiomechanicsandmedicineinswimmingXi
Figure 1. Specifically designed structure to support the electronic
ALGE touchpad (TPI), to be placed at any distance from the wall on
either side of the 25 m or 50 m pool.
results
The change in start times did not display significant differences between
groups. However, data showed that both groups reduced their starting
times, even the group that did not receive feedback after the effort (Average
improvements: EG: 0.30 s vs CG 0.11 s). The fact that the CG
group improved due to practice without feedback may explain the lack
of significant differences between the improvements in the EG and CG.
However, the improvements were greater within the EG (5.2%) than
control (2.2%), where the swimmers received TKR after the practice. In
order to check the significance of the improvement within each group, a
related samples t-Test was performed. Results showed significant differences
in both groups, with a greater significance level in the EG, at the
four distances analyzed (Table 2).
At the previous video recording, most swimmers emerged to the
surface before 10 m. For that reason, the decision was made to focus
the training on 10 m rather than 15m, in order to avoid an erroneous
start measurement related to the swim phase after surfacing. Taking into
account the total number of repetitions, the performance improvement
was greater at the more practiced distances (start followed by freestyle
swimming up to 10m and start followed by underwater dolphin kicking
up to 10m) (Table 2).
Table 2. Differences between pre-test and post-test in both groups (Experimental
– EG and control group CG). Results from related samples
t-Test.
Pre-test Post-Test
Mean (s) SD Mean (s) SD t-test
15 m free
EG
1 8.02 0.78 7.87 0.79 **
10 m DK2 10 m free
5.68
4.84
0.75
0.53
5.38
4.58
0.73
0.49
***
***
10 m glide 3 7.18 1.11 7.04 1.09 **
15 m free 8.17 0.81 8.07 0.81 *
CG
10 m DK1 10 m free
5.84
4.95
0.81
0.57
5.73
4.84
0.81
0.58
**
**
10 m glide 7.41 1.11 7.31 1.10 *
1. Free. Start followed by freestyle swim until 15m 2. DK: Underwater
dolphin kicking. 3. Start + Gliding until hands contact (TPI) at 10m.
To represent the effectiveness of the experimental training, the start improvement
as a percentage between the times achieved before and after
the training sessions was calculated. As a result, the improvement percentage
was 3% greater in the experimental group, with greater differences
on the more practiced distances (Figure 2). This seems to indicate
250
that giving accurate feedback related to the start duration produces more
significant effects than just systematic repetition.
Figure 2. Percentage improvement in start times before and after training
in the experimental and control groups.
As a consequence of the statistical results, the data for individual swimmers
were analysed. The starting times as a function of the number of
training sessions for two subjects; the one with greatest improvement
and the one with the least improvement for both groups were examined
(Figure 3). Comparing times, (Figure 4) it was seen that performance
tended to be more consistent within the EG (lower differences between
the best time and the average time among the sessions). Similar times
Biomechanics and Medicine in Swimming XI / Chapter 4 Training Page 25
seem to indicate a more constant and uniform performance at the end
of the training period.
10m Free Swim (s)
5,2
5
4,8
4,6
4,4
4,2
6,8
6,6
6,4
6,2
6
Experimental Group (Subject 39)
Best
Average
1 2 3 4 5 6 7 8 9 10
S E S S I ON S
Control Group (Subject 21)
Best
Avera
5 8
Figure 3. Individual performance evolution (10m Free) along the sessions.
Dif. Before Dif. After
Figure 0,4 3. Individual performance evolution (10m Free) along the ses-
sions.
Dif. between Best & Average (s)
0,35
0,3
0,25
0,2
0,15
0,1
0,05
0
S21 S16 S09 S73 S39 S15 S75 S25
Control Group Experimental Group