4.
Results and Discussion
1.
Dynamics
of the
“pure”
swimming speed
during
100-m
swimming.
The
data in table 1 contains
the
values of “pure” swimming
speed (V)
in
each of the
4
sections and
the average “pure”
V during 100m
freestyle
race
in boy-swimmers
11-16 years of age.
Within
each
age group the same tendency
was revealed
- swimming speed decreased from
the first lap
to the
last
(p<0.01-0.001).
Comparison
of the data for consecutive
ages shows
that swimming
speed values at every lap of “pure” swimming and average racing
speed in
the 100m freestyle
event increased with the age of the swimmer.
On the basis of year-by-year differences we assume that the
most rapid growth of the
V
occurs
from
11 to 13 years of age.
A slow increase
of
V at
13-14 years is
followed
by a
second
acceleration from
14 to 16 years
of age.
Table
1.
Swimming
speed
(V (m·s-1)) at
consecutive
laps
during
maximal
100-m
freestyle
swim
in
boy-swimmers
11-16 years
of age.
Values are mean
+ SD.
___________________________________________________________________________
A g e
C
o h o r
t s
Lap
|
11 (n=39)
|
12 (n=30)
|
13 (n=36)
|
14 (n=47)
|
15 (n=37)
|
16 (n=36)
|
1-st 25
m
|
1.19+0.09
|
1.33+0.12
|
1.53+0.08
|
1.60+0.09
|
1.68+0.08
|
1.70+0.09
|
2-nd 25 m
|
1.09+0.19
|
1.19+0.12
|
1.43+0.08
|
1.54+0.09
|
1.56+0.08
|
1.65+0.06
|
3-d
25 m
|
1.06+0.09
|
1.13+0.16
|
1.40+0.10
|
1.40+0.07
|
1.44+0.09
|
1.55+0.06
|
4-th
25 m
|
1.01+0.18
|
1.11+0.21
|
1.28+0.08
|
1.40+0.06
|
1.40+0.10
|
1.54+0.07
|
Average
|
1.09+0.10
|
1.19+0.13
|
1.41+0.16
|
1.48+0.11
|
1.52+0.07
|
1.61+0.06
|
___________________________________________________________________________
2.
Dynamics
of the SR
during
100-m
swimming.
The
age dynamics of
the values of SR and SL
during competitive swimming in
100m
freestyle
represents high interest because swimming speed is the derivative namely
from SR and SL.
The values
of
SR during 100m swimming for
each age group are
shown in Table 2. It
should be noted that the
mean
values
of swimming tempo are almost identical in all age cohorts.
The values of SR found in boys 11-16 years of age were much higher than
those reported by Pyne and Trewin (2001) for the finalists of the Sydney
Olympic Games competing in the 100m freestyle, but very close to the
values of SR demonstrated by Olympians in the 50m freestyle. As we
assumed before these studies, SR in young swimmers should decrease with
the age due to somatic growth and the increase of strength and
endurance. Nevertheless, we did not establish any consistent and
significant decrease of average SR with age (see Supplementum, table 4).
In every age cohort we found young swimmers with high as well as low SR.
Table
2.
Stroke
Rate (cycles
· min-1)
at
consecutive
laps
during
maximal
100-m
freestyle
swim
in
boy-swimmers
11-16 years
of age.
Values are mean
+ SD.
___________________________________________________________________________
A g e
C o
h o
r t s
Lap
|
11 (n=39)
|
12 (n=30)
|
13 (n=36)
|
14 (n=47)
|
15 (n=37)
|
16 (n=36)
|
1-st 25 m
|
63.4+
9.3
|
61.4+
5.8
|
64.1+
6.4
|
65.9+
5.6
|
65.6+
8.7
|
62.2+
5.6
|
2-nd
25 m
|
60.4+
5.2
|
56.9+
4.5
|
58.4+ 6.0
|
59.6+
3.9
|
58.9+
4.2
|
58.4+
5.1
|
3-d 25 m
|
56.4+
4.7
|
52.7+
4.5
|
55.1+
6.1
|
58.3+
5.2
|
56.5+
6.6
|
56.4+
4.8
|
4-th 25 m
|
52.6+
4.7
|
51.4+
4.0
|
53.9+
6.7
|
56.7+
4.0
|
55.2+
6.5
|
56.6+
4.6
|
Average
|
58.2+
6.1
|
55.6+
3.8
|
57.9+
5.7
|
60.1+ 3.9
|
59.0+ 7.3
|
58.4+
4.6
|
___________________________________________________________________________
It
looks like swimmers choose their own most “comfortable” stroke rate
at earlier ages (at the age of 11-12 years). Hence it should become a
prime concern for coaches to help age groupers to produce a more
economical stroke rate and to teach them to concentrate more on
increasing the stroking distance to an optimal level.
We
found consistent decreases
of SR from lap to lap
for
boy-swimmers
of all
age cohorts.
Decrease
of SR from lap 1 to lap 2, lap 2 to lap 4, lap 1 to laps 3 and 4 was
significant (p<0.01-0.001, see Supplementum, table 5).
It
follows from the results of our studies that the decrease of swimming
velocity is related to the reduction of SR due to fatigue. This supports
the data of Barden
and Rorke
(1999),
who found that changes
in swimming velocity only affected stroke rate, not stroke length
and a decreased
stroke rate might serve as a useful indicator of loss of anaerobic power.
Earlier MacArdle and Reilly (1992) suggested that a fall in SR during
competitive racing is a consequence of the decrease in pulling velocity.
During
a 100m race young swimmers did not demonstrate any compensatory
increase of SR
in order to prevent slowing down of swimming speed. It is interesting
that similar lap-by-lap
decrease of SR was found for the male finalists at the Pan Pacific
Swimming Championships (1999) reported by a research group from the
Australian Institute of Sport (the winner had stroke rate respectively
57.3-53.3-52.9-51.3. Total decrease of SR was 10.5%!).
3.
Dynamics
of the SL
during
100-m
swimming.
The
average value of SL
(Table
3) increased from
the 11 to 16 years of
age cohorts with
periods of fast gain between
11-13
(p<0.001)
and
15-16
years
(p<0.05). Minor slow down in the growth rate of SL took place between
13 and 14 years of age. These
results are in agreement with our previous research related to the
growth of the
dynamic
parameters of pulling actions in young swimmers (Vorontsov,
Binevsky, 1991).
In
accordance with
that
data
at
the age of 11-12 years occurs
a
significant
increase of pulling power and efficiency
related to improvement of core swimming skills at
the early
stages of multi-year
training.
Following
increase of the SL at
the age of 15-16
years,
as we assumed, may
be connected with a
period
of fast increase
of
muscle
mass and power (Vorontsov et al, 1999).
Table
3.
Stroke
length
at
consecutive
laps
during
maximal
100-m
freestyle
swim
in
boy-swimmers
11-16 years
of age.
Values are mean
+ SD.
___________________________________________________________________________
A g
e C o h o
r t
s
Lap
|
11 (n=39)
|
12 (n=30)
|
13 (n=36)
|
14 (n=47)
|
15 (n=37)
|
16 (n=36)
|
1-st 25
m
|
1.13+0.05
|
1.30+0.16
|
1.43+0.16
|
1.46+0.11
|
1.54+0.20
|
1.64+0.17
|
2-nd
25 m
|
1.08+0.06
|
1.26+0.14
|
1.47+0.15
|
1.55+0.12
|
1.59+0.09
|
1.70+0.17
|
3-d 25 m
|
1.03+0.12
|
1.29+0.12
|
1.52+0.13
|
1.44+0.12
|
1.53+0.09
|
1.65+0.16
|
4-th 25 m
|
1.15+0.06
|
1.30+0.11
|
1.42+0.15
|
1.48+0.15
|
1.52+0.19
|
1.63+0.16
|
Average
|
1.12+0.06
|
1.28+0.13
|
1.46+0.15
|
1.48+0.13
|
1.55+0.19
|
1.65+0.17
|
___________________________________________________________________________
With
regards
to
the change of SL
from lap to lap we did
not
find any
significant
fall in
that parameter during
the race in
all age cohorts.
An increase of SL at the last 25-m section in 11-12 year old boys may
reflect the contribution of leg kick with the onset of fatigue, but the
role of the leg kick was beyond our attention
in this study.
The
highest value of SL
for
boy-swimmers
of 13-16 years age was produced
in
the
2nd
25m section,
where despite
a
much lower
SR
than during the first lap, swimming
speed was
still higher
than average racing V.
Exactly
the same tendency was found in finalists of the 1999 Pan Pacific
Championships (AIS Biomechanics, 1999) - 7 of the 8 elite swimmers had
the largest StD in the 2nd 25m section. During
swimming at
the
3rd
and 4th 25-m
sections
of the race,
young swimmers demonsrated a
non-significant
decrease of SL
which together with a significant reduction of SR caused significant
decrease in swimming speed (p<0.001).
We
suggest
than
the quality of arm pulls during swimming in
the
second 25m section
is the best
and the SR/SL ratio is optimal (moderate SR, maximal SL while swimming
speed is above average distance speed).
It may be used as a model in the process of technical preparation
of age group swimmers.
The
accent on the maintenance of large SL and constant moderate SR will mean
an introduction of reasonable physical difficulty into a process of technical
preparation
and,
thus, will facilitate both physical and technical preparedness of young
swimmers.
|