3 / cet
to establish the
age dynamics of stroke
stroke length (SL)
and swimming speed (V)
aged 11-16 years. The subjects of this study were 225 boy-swimmers from 3
swimming schools and the State College of Olympic Reserves (Moscow). Each
swimmer performed maximal 100m freestyle swim from a dive. The swim was
recorded using a video camera (frequency 50 Hz) and VHS-VCR installed on a
trolley, which accompanied a swimmer along the pool deck throughout the
entire swim. Video records of swimming with electronic time data were
processed and velocity of “pure” swimming at
the 100m race, as well as SR
of “pure” swimming were calculated. No
differences were found
average and lap-by-lap values of SR.
during the race changed insignificantly. The decrease
end of 100m race
in all age cohorts should
be attributed primarily to the decrease of SR.
young swimmers, stroke rate, stroke distance, swimming velocity.
rate (SR) and stroke length
ratio as well as changes
as macro characteristics of
dynamics of these characteristics during
was the subject of numerous
et al., 1984; Lipsky, Abramov, 1988, Wakayoshi
et al., 1992; Wirtz
W., Wilke K.
Pyne & Trewin,
2001 and many others). The subjects of those studies were physically
able to control and
voluntary change the SR
the race in order to reduce
decrease of the swimming speed
to accumulation of fatigue.
swimmers learn to control the structure and efficiency of the movement
while they grow up and mature in
the process of a
5-7- year training
they pass through pre-pubescent
and pubescent stages
rapid physical growth and motor development
motor abilities and fitness
may be reflected in the “macro”
efficiency of sport techniques. Knowledge
age particulars and year-by-year dynamics of technical characteristics may
allow us to
control and correct the process of
technical preparation in young swimmers.
to establish the
age dynamics of SR,
and swimming speed in young swimmers
(boys aged 11-16 years) during
freestyle and thus to establish the formation of special swimming skills
during the growth from 11 to 16 years of age.
subjects of this study were 225 boy-swimmers 11 to 16 years of age from 3
swimming schools and the State College of Olympic Reserves (Moscow). The
experiment was held in the 50m swimming pool of the Russian State Academy
of Physical Education. Each swimmer performed a maximal 100m freestyle
swim from a dive. Only those swims with a time less than PB+2 s (personal
best time + 2 s) were taken into consideration.
the purpose of this study the
entire distance was conditionally
Each swim was recorded using a video camera (recording frequency 50 Hz) and VHS-VCR with TV display installed on a trolley. The trolley, towed by operator-camera men, accompanied each swimmer along the pool deck throughout the entire swim. During recording operator kept swimmer’s image in the middle of TV display. The optical axis of the camera was perpendicular to the swimming direction. The starting sound signal was synchronized with a flashlight to indicate the beginning of the race on videotape. A signal from an electronic timer was recorded on the same videotape as the swimming race throughout the time of video recording.
records of swimming with electronic time data were processed and the
following characteristics were calculated:
of “pure” swimming (V) in
of “pure” swimming.
SR (cycles · min-1) for each lap was determined as:
: tn x 60
arm pulls (each arm pull constitutes a half of freestyle’s swimming
cycle) completed by
“pure” swimming and tn - time of “pure” swimming
of the race.
every lap of “pure” swimming were determined as
length of lap divided by SR.
0.5·AP1 (from 7.5 to 25)
· 60; SL1
Average values of V, SR and SL per distance were calculated based on individuals’ average values. T-statistics (ANOVA, SPSS) was used to establish significance of the differences in V, SR, and SL between age cohorts and lap-by-lap changes of V, SR, and SL within each age cohort (results of analysis are given in Supplementum, tables 4 and 5).
Results and Discussion
data in table 1 contains
values of “pure” swimming
each of the
the average “pure”
V during 100m
11-16 years of age.
age group the same tendency
- swimming speed decreased from
the first lap
of the data for consecutive
speed values at every lap of “pure” swimming and average racing
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
11 to 13 years of age.
A slow increase
13-14 years is
14 to 16 years
(V (m·s-1)) at
A g e
o h o r
of the SR
age dynamics of
the values of SR and SL
during competitive swimming in
represents high interest because swimming speed is the derivative namely
from SR and SL.
SR during 100m swimming for
each age group are
shown in Table 2. It
should be noted that the
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.
A g e
r t s
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.
found consistent decreases
of SR from lap to lap
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).
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
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.
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%!).
of the SL
average value of SL
3) increased from
the 11 to 16 years of
age cohorts with
periods of fast gain between
(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
parameters of pulling actions in young swimmers (Vorontsov,
the age of 11-12 years occurs
increase of pulling power and efficiency
related to improvement of core swimming skills at
stages of multi-year
increase of the SL at
the age of 15-16
as we assumed, may
be connected with a
of fast increase
mass and power (Vorontsov et al, 1999).
e C o h o
the change of SL
from lap to lap we did
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.
highest value of SL
of 13-16 years age was produced
than during the first lap, swimming
than average racing V.
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
and 4th 25-m
of the race,
young swimmers demonsrated a
decrease of SL
which together with a significant reduction of SR caused significant
decrease in swimming speed (p<0.001).
the quality of arm pulls during swimming in
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.
accent on the maintenance of large SL and constant moderate SR will mean
an introduction of reasonable physical difficulty into a process of technical
thus, will facilitate both physical and technical preparedness of young
the process of
growth and multi-years training,
consecutive sections of the
of rapid increase of V and SL in boys (12-13 and 15-16 years of age)
coincide with periods of rapid growth
of maximal strength
anaerobic lactic ability
(Vorontsov et al., 1999).
age-related differences were found
average and lap-by-lap values of SR.
all age cohorts
seems that the individual rhythm of swimming movement is formed in boys
already at the age of 11-12 years.
end of 100-m
distance in all age cohorts
be attributed to the decrease of SR. No temporal
compensatory increase of SR
in order to delay the decrease of V was found.
investigation of V,
SR and SL
in young swimmers of different sexes and ages
have considerable topical significance.
AIS Biomechanics (1999) Swim Competition Analysis: Pan Pacific
Championships, Sydney, August 22-29 1999. (Scientific guidance by
B.Mason), AIS, Sydney.
Barden, J. M.,
& Rorke, S. C. (1999). Stroke parameter relationships in a repeated
swim interval training set. Medicine
and Science in Sports and Exercise,
Haljand R., Tamp T., Kaal P. (1984) Models of technique of the swimming
strokes with methods of their perfection and control. Pedagogical
Institute of E.Vilde, Tallin.
Lipsky E.V., Abramov A.B. (1988). Competitive
performance of sprint-swimmers on the distance 50 m. In: Plavanie,
pp.13-16. FiS, Moscow.
McArdle D., Reilly T. (1992) Consequences of altering stroke parameters
in front crawl swimming and its simulation. In: Biomechanics and Medicine in Swimming. Swimming Science VI,
(Editors: D.MacLaren, T.Reilly and A.Lees), E & FN SPON, Cambridge.
Pyne D., Trewin C. (2001). Analysis of stroke rates in freestyle events
at 2000 Olympics. Swimming in
Australia, January-February 2001, downloaded from http:/www.ascta.com
(ASCTA Online Library).
Vorontsov A.R., Binevsky D.A. (1991) Time and dynamic parameters of
front crawl arm pull in boy-swimmers 11-16 years of age. Annual scientific report of Swimming Department. Central State Institute
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Vorontsov A.R., Dyrco V.V., Binevsky D.A., Solomatin V.R., Sidorov N.N.
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