Biomechanics and Medicine in Swimming XI

BiomechanicsandmedicineinswimmingXi
Physiological Responses and Performance
Characteristics of 200m Continuous Swimming and
4x50m ‘’Broken Swimming’’ with Different Rest
Intervals
Beidaris, n., Botonis, P. and Platanou, t.
Faculty of Physical Education and Sport Science, University of Athens, Greece
The purpose of the present study was to investigate the physiological responses
and performance characteristics of ‘’broken’’ swimming (4x50m)
with different rest intervals (5, 10 and 20s) compared with those of continuous
swimming (200m) during maximum intensity free-style swimming.
Twelve voluntary swimmers of competitive level (aged: 14-17
years) were tested. Significant differences were observed in performance
time and heart rate between continuous and «broken» swimming with
resting interval of 20s (F=4.27, P=0.009 and F=3.31, P=0.03, respectively).
However, no differences were found in blood lactate and oxygen
consumption. In conclusion, it seems that even if the physiological
responses were similar between conditions, the performance
characteristics were higher in the condition of broken swimming
with 20s resting interval.
Key words: Vo 2 , lactate, heart rate, performance, speed, number of
strokes
IntroductIon
In swimming training, various methods have been employed for the
improvement of swimming endurance and speed. ‘’Broken’’ swimming
is a mode of interval and repeated training for maintaining high rate
and speed of swimming of a distance with maximum intensity (“broken”
swim, Maglischo 1993). According to this method, the total swimming
distance is divided into smaller distances with short rest intervals during
which athletes swim to their limits, maintaining the highest speed
possible. The rest intervals between swims could be either long (20 s) or
short (5 s), during which swimmers maintain the same rate and speed
throughout the total distance. The total time is estimated by subtracting
the rest interval time from the total time of the total distance. Additionally,
the above method is mainly used as a test of performance in a given
distance before competition.
The physiological responses and the performance characteristics are
very important for a coach who needs to analyze the training data and to
gain feedback for the results of a method as a way for achieving the competition
goals. It is known that heart rate is an exercise intensity index as
are blood lactate and maximal oxygen consumption. In particular, during
high intensity exercise, the heart rate and heart muscle contractility are
increased to deliver more blood to exercising muscles. Heart rate is considered
as a main training guide by many researchers (Chen et al. 2002,
Niewiadomski et al. 2007).
Moreover, lactic acid is produced during exercise and it is well established
that during high intensity exercise, the lactate production is
raised. During the first stages of exercise, O 2 deficit is evident, and as
a result lactic acid is increased for energy production. The blood lactate
concentration is another main index of exercise intensity (Billat 1996).
Oxygen consumption is also an index of exercise intensity and can be
used to evaluate the contribution of aerobic energy during exercise (Fernandez
et al., 2003). It shows the cardiovascular and muscle ability of
the body to consume O 2 per unit time. The increment of oxygen consumption
is linear and is related to the exercise intensity.
However it is not known, if the physiological responses and performance
characteristics are similar between interval and continuous
training. The purpose of this study was to investigate: 1) the physiological
responses of ‘’broken’’ swimming (4x50m) with different resting intervals
compared with those of continuous swimming (200m) during
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maximum intensity free-style swimming and 2) which resting interval
in ‘’broken’’ swimming, contributes to the development of higher swimming
speed with similar physiological demands compared to those of
continuous swimming. The hypotheses in this study are that 1) the maximum
lactate concentration and oxygen consumption would be similar
at the end of the 200m swimming, regardless of the resting interval
between the 50m swims. 2) The heart rate during the 200m swimming
would be expected to be different because the intensity of exercise would
be dependent on the previous resting interval and 3) the performance
related characteristics in ‘’broken’’ swimming would be expected to be
different. It is expected that a long resting interval would contribute to a
higher swimming performance.
Methods
Twelve swimmers (aged: 14-17 years) with at least five years of training
age were tested in 4 exercise conditions: in 200m and in 4x50m of
free-style swimming with 5, 10 and 20 s rest intervals between swims. In
all sets, A) Physiological parameters: 1. oxygen consumption (VO2000
Breeze Lite, MedGraphics, USA) 2. blood lactate concentration (Accusport,
Boehringer, Germany) 3. Heart rate (Polar, Vantage NV, Finland)
B) Performance characteristics: recording of performance time,
mean speed and number of strokes. C) Rate of perceived exertion (Borg
scale), were measured.
In the beginning, a VO 2 max test (400m free style swimming) was
conducted in order to estimate the oxygen consumption as a percentage
(%) of VO 2 max by backward extrapolation. The reliability and validity
of backward extrapolation has been previously tested (Leger et al. 1980,
Montpetit 1981). According to that method, the air is collected at the
end of exercise in 4 different times of 20 s and then a linear backward
regression curve is conducted. Afterwards, each participant swam 200m
and on a separate day 4x50m free style swimming of maximum intensity
with 5, 10 and 20 s resting interval between swims in a random order.
At the end of each condition the O 2 deficit was calculated by measuring
the exhaled air for 2-min during recovery. Immediately after the
swimming test, the participants expired directly into a respiratory valve
that was connected to the metabolic card. During each test, heart rate
was recorded every 5 seconds. The rate of perceived exertion which is
considered as a fatigue index was measured at the end of the test by the
Borg scale. Blood samples for lactate concentration measurement were
taken at 3, 5 and 7 minutes of recovery. Moreover, the performance time
was recorded for each 50m swim and for the total distance by a hand
chronometer.
All results are expressed as mean values (±SD). One way ANOVA
for dependent samples was used to define the overall differences in each
variable. Furthermore, one way ANOVA for dependent samples with
repeated measurements was used to define differences in each variable
between 50m swims. A Tukey test was employed to assign specific differences
in the analysis of variance. Statistical significance was set at
P