Biomechanics and Medicine in Swimming XI

BiomechanicsandmedicineinswimmingXi
swimmers, very long training intervals (repetitions of 500 m) swum at
lactate threshold would lead to greater oxygen uptake, higher stroke rate,
and shorter stroke length than those observed during intervals of shorter
distance (repetitions of 100 m).
Methods
Seven long-distance male swimmers competing at the national and international
level participated in this study.
Table 1. Individual anthropometric characteristics and training content.
S
260
Age
(Y)
Weight
(kg)
Height
(cm)
v LT-
(km)
v LT+
(km)
1 23 61 176 2100 380
2 22 74 188 1900 290
3 20 75 185 2050 370
4 21 69 175 2200 303
5 20 76 182 2200 320
6 29 69 174 2350 352
7 20 76 182 2200 330
M 22 71 180 2143 335
SE 3.2 5.5 5.4 143 34
v LT-, annual training volume at low intensity below the lactate threshold.
v LT+, annual training volume at high intensity above the lactate
threshold .
All participants completed three experimental sessions in a 50-m open
pool (26°C) during one week of standardized training. The first training
test consisted in a progressive incremental test to exhaustion. The
other tests were two randomized interval sessions – 6 x 500 m (IT6x500 )
or 30x100 m (IT30x100 ) – performed at the velocity corresponding to
lactate threshold (vLT). During each IT session, the time spent at 90%
above 2 O V� max and 90% above maximal heart rate (HRpeak ) were determined
retrospectively. The incremental test included five consecutive
300-m swims separated by 30s of rest. The speed of each increment was
determined from the best performance of each swimmer in the 400m
freestyle event measured during the month preceding the test. The
speed for the first 300-m was 30-s slower than the average 300-m pace
over the 400-m best performance and this time was then reduced by
increments of 5 s for each consecutive 300-m until the final 300-m at
the swimmer’s fastest speed. Swimming speeds were monitored with
Aquapacer ‘Solo’ (Challenge and Response, Inverurie, UK) so that each
swimmer could match auditory signals with visual markers positioned
every 12.5 m along the border of the pool. Blood lactate level (expressed
in mM/L) was determined from a fingertip blood sample which was
analyzed immediately using a portable lactate analyzer (Lactate Pro,
Arkray, Japan). Breath-by-breath respiratory data were collected with
a portable gas analyzer (Cosmed K4b2, Rome, Italy) connected to an
Aquatrainer snorkel (Cosmed, Rome, Italy). Heart rate (HR) was recorded
using a belt system (Polar Electro, Finland). The lactate threshold
(LT) was determined by two independent observers using the first
inflexion method applied to the linear relationship between lactate level
and velocity associated with a 1mmol·l-1 increase in serum lactate above
the baseline level. HRpeak (expressed in beats·min-1 ) was defined as the
mean highest HR measured over 15s during the test.
During the interval training (IT), the swimmers were kept informed
of their velocity using the protocol described above. Swimmers were
encouraged orally to sustain their velocity despite increasing exhaustion
throughout the set. Swim times (s) were systematically recorded for
each 500 and 100-m repetition. Because the swimmers were wearing a
snorkel, they used open turns. During a pilot run, the time needed to execute
a turn with the snorkel was estimated individually with an average
time of 1±0.37 s compared with a conventional tumble turn. The velocity
(m·s-1 ) was calculated by dividing the length of each repetition (100-m
or 500-m) by the time with individual correction for number of turns.
The actual velocity for each 5x100m workout was averaged for a comparison
with IT6x500 . Mean stroke rate (SR) (cycle·min-1 ) was measured
in a 25-m central zone using a base 3 chronometer (Seiko, base 3, Japan).
Stroke length (SL) was calculated for each 50 m by dividing the mean
velocity by SR. Expired gases collected breath-by-breath were monitored
continuously and recorded every 5 s. VO2 �
mean for the two IT6x500 and IT30*100 sessions were calculated as was the time of swimming above
90% of VO2 � max (T>90%). Breath samples were then averaged over 30
s and 2 O V� peak and HR peak were measured and expressed in % of VO2 �
max. Serum lactate level was measured at the end of eat IT session.
results
Stroke length was longer during IT 30x100 than IT 6*500 (2.45 ± 0.16 vs.
2.30 ± 0.16 m, P < 0.05) (Figure 1) and stroke rate tended to be lower
(35.4 ± 3.3 vs. 37.8 ± 3.2, s·mn -1 , P = 0.08).
SL (m)
2,8
2,7
2,6
2,5
2,4
2,3
2,2
2,1
2
1 2 3 4 5 6
Figure 1. Mean ± SE Stroke length (SL) (m·stroke -1 ) during each
stage of the 30 x 100-m (IT 30x100 ) (Broken line with white diamonds
shaped) and 6 x 500-m (IT 6x500 ) IT sessions (Continuous line with
black squares). Stroke length was higher (P < 0.05) for (IT 30x100 ) than
for (IT 6x500 ).
There was no significant difference in swimming velocity between
IT6*500 and IT30*100 for each 500 m. Expressed in % v VO2 �
max and %
vLT, swimming velocities were 96.4 ± 3.4 and 99.2 ± 3.6% for IT6*500 and 96.7 ± 3.4 and 99.4 ± 4.4% for IT30*100 respectively. Although the
swimming velocity was similar during IT6*500 and IT30*100, VO2 �
mean ,
VE �
mean , BL and RPE were greater for IT6*500 than IT30*100 (63.8±3.9 vs.
57.3±3.1 mL.kg-1 ·min-1 ; 79.6±18.8 vs. 73.2±10.5 mL·kg-1 ·min-1 ; 4.1±1.2
vs. 3.2±1.4 mmol·L-1 ; 17.3±2.4 vs. 14.7±3.1 a.u. P < 0.05). T>90% was
greater for IT6*500 (1357 ± 288 vs. 562 ± 326 s, P < 0.05) (Table 2).
dIscussIon
The major finding of this study is that the long interval training set
(IT6*500m ) which was performed at vLT displayed higher physiological
responses and longer time sustained above 90% VO2 �
max compared with
the shorter interval training (IT30*100m ). This is in agreement with the
pioneer work on physiological response to interval training conducted
by Astrand et al., (1960) who demonstrated that for exercise performed
at 98% of the workload corresponding to VO 2
�
max , long interval exercise
allowed athletes to attain VO 2
�
max whereas short-interval training
led to sub-maximal response (63% VO 2
�
max ). Conversely, our results are
not in agreement with those reported by Bentley et al. (2005) who compared,
in eight elite swimmers, two interval training sessions comprising
4 repetitions of 400m or 16 repetitions of 100m completed at a velocity
representing 25% of the difference between ventilatory threshold and
VO2 �
max (Δ25%). They were unable to find any significant difference
in the physiological responses. The apparent discordance with our data
might be attributed to the shorter intervals (400 vs. 500 m), the smaller
exercise volume (1600 vs. 3000 m).
For elite long-distance swimmers, training at vLT over long intervals
would probably be particularly useful as has already been reported