Available online at www.sciencedirect.com
Journal of Science and Medicine in Sport 14 (2011) 363–368
Original Research
Physiological responses during interval training at relative to critical
velocity intensity in young swimmers
Argyris G. Toubekis a,b,∗ , Anthoula Vasilaki b , Helen Douda b , Vassilios Gourgoulis b ,
Savvas Tokmakidis b
a
Kapodistrian University of Athens, Faculty of Physical Education and Sports Science, Department of Aquatics, Athens, Greece
b Democritus University of Thrace, Department of Physical Education and Sports Science, Komotini, Greece
Received 11 September 2010; received in revised form 27 February 2011; accepted 3 March 2011
Abstract
Objectives: The purpose of this study was to examine the physiological responses on three interval training sets performed at intensities
relative to the critical velocity which was calculated from two different combinations of distances using a 2-parameter linear model. Methods: In
a controlled repeated measures design, ten male well trained swimmers (age: 15.2 ± 1.2 years) swam 5 × 400-m, 10 × 200-m and 20 × 100-m
on separate days with rest to swimming ratio 1:8, aiming to maintain the critical velocity calculated from distances of 50, 100, 200, 400-m (CV4 )
or 200, 400-m (CV200–400 ). Results: The sustained velocity on the 5 × 400-m was lower compared to CV4 and velocity on the 20 × 100-m was
higher compared to CV200–400 . The velocity on the 10 × 200-m was kept similar to both CV4 and CV200–400 (5 × 400-m: 1.27 ± 0.07 vs. CV4 :
1.33 ± 0.09 m s−1 , p < 0.05; 20 × 100-m: 1.32 ± 0.02 vs. CV200–400 : 1.28 ± 0.09 m s−1 , p < 0.05; 10 × 200-m: 1.30 ± 0.10 m s−1 vs. CV4 and
CV200–400 , p > 0.05). The blood lactate concentration increased after 1200 compared to 400-m (4.45 ± 0.23 vs. 5.82 ± 0.24 mmol l−1 , p < 0.05)
and was no different between sets (p > 0.05). Stroke rate and stroke length were not different between and within conditions (p > 0.05). Heart
rate during the recovery periods was lower in the 5 × 400-m compared to 10 × 200-m and 20 × 100-m training set (p < 0.05). Conclusion:
Interval swimming pace can be adjusted in relation to critical velocity calculated from distances of 200 and 400-m or from distance of 50,
100, 200, 400 m. When the distance of repetitions is increased from 100 to 200 and 400-m the velocity should be reduced by 2% to achieve
similar metabolic responses.
© 2011 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
Keywords: Aerobic endurance; Slope of distance–time; Age-group swimmers
1. Introduction
The application of a reliable test is required in order to
evaluate swimming capacities and delimitate the interval
swimming training pace.1 The slope of distance vs. time relationship which is defined as the critical swimming velocity
(CV) is accepted as a valid index for the evaluation of aerobic endurance capacity of swimmers.1–3 Furthermore, it has
been suggested that CV can be used for the design and control
of pace during interval swimming training.3 A prerequisite
for the use of CV pace for training prescription is to locate it
across the exercise intensity domains. Although this question
∗
Corresponding author.
E-mail address: atoubekis@phed.uoa.gr (A.G. Toubekis).
is still under research for swimmers, it seems that swimming
at the CV calculated by distances of 100–800 m is located
within the severe exercise intensity domain (i.e. above the
maximum lactate steady state; MLSS).4 This is because continuous swimming at this velocity causes exhaustion in less
than 25 min, while it progressively increases blood lactate
values and oxygen uptake responses near VO2 max.4 However, intermittent swimming at the velocity corresponding to
CV (10 × 400-m, 4 × 400-m, 5 × 400-m) can be sustained
for a long period with a steady,4–6 or increasing7,8 blood
lactate concentration. In the above mentioned studies the
combination of distances used for the CV determination
was not the same and this may have caused over-estimation
or under-estimation on the prescribed velocity.4,6,7 In addition, a significant change or no difference on the evolution
1440-2440/$ – see front matter © 2011 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.jsams.2011.03.002
364
A.G. Toubekis et al. / Journal of Science and Medicine in Sport 14 (2011) 363–368
of stroke mechanics during a training set of repetitions has
been reported,7,8 whereas repetitions of 400-m distance have
been used to examine the sustainability of the CV velocity
in previous studies.5–7 Using shorter (i.e. 100, 200-m) compared to longer (400-m) distance repetitions an increased
sustained velocity is expected, despite similar metabolic
responses after the training set.9 The sustained velocity may
also increase by extending the resting interval,9 and changes
in the interval duration at the same intensity may alter the
energy system contribution.10,11 It is interesting and of practical value to examine the physiological responses during
interval swims around the CV intensity using repetitions
of distances that have been previously suggested for aerobic endurance improvement of swimmers, such as 200 or
100-m.12 The purpose of this study was to compare the physiological responses, stroke parameters changes and the ability
to sustain a velocity relative to CV calculated from two different combinations of distances during interval training sets
using repetitions of 100, 200 and 400-m.
2. Methods
Ten male swimmers (age: 15.2 ± 1.2 years, body mass:
67.5 ± 7.3 kg, height: 1.72 ± 0.04 m) participated in the
study. All swimmers were trained for 1 h and 45 min
to 2 h daily participating in six–nine training sessions
per week, covering distances of 4000–5000 m per day
(30,000–42,000 m per week). The swimmers were specialized in various swimming techniques and competitive
distances and their best 200-m freestyle record corresponded
to 81 ± 5% of the present youth world record and 462 ± 76
FINA points for a 50-m pool (Supplemental file 1). The swimmers and their parents were informed in detail about the
experimental risks and procedures and signed an informed
consent document prior to the investigation, which was completed eight to twelve weeks prior to the national age-group
championship. The investigation was approved by the Institutional Review Board for use of Human subjects according
to the Helsinki declaration.
Within four consecutive days all swimmers performed
all-out efforts over distances of 50, 100, 200, 400-m after
a standard warm-up (400-m self-paced swim–200-m leg
kick–200-m arm-pull, 4 × 50-m progressively increasing
intensity, 2 × 10-m sprints, 100-m cool-down). The all-out
efforts were performed in a counterbalanced order and started
from the blocks. The critical velocity was calculated using
all four distances (CV4 ) and using distances of 200 and
400-m (CV200–400 ).2,5 Following the CV4 and CV200–400
calculation, the swimmers completed three different experimental conditions in a controlled repeated measures design.
In each experimental condition one of the following interval training sets (total distance of 2000-m for each set) was
applied: (i) five repetitions of 400-m (5 × 400-m), (ii) ten
repetitions of 200-m (10 × 200-m), (iii) twenty repetitions of
100-m (20 × 100-m). The order of experimental conditions
was counterbalanced for nine swimmers and was randomly
assigned for the tenth swimmer. The interval training sets
were performed a week apart and were completed within a
period of 15–20 days for each swimmer. The interval duration was individually adjusted based on the duration of the
first repetition, applying a rest to swimming ratio 1:8 and was
kept the same during successive repetitions of each set. The
swimmers were instructed for their pace and were encouraged to maintain a velocity corresponding to CV4 keeping
their head at the level of one of the experimenters who was
walking along the side of the swimming pool. The experimenter adjusted the required pace while looking at a digital
chronograph. In case a swimmer was not able to follow the
CV4 pace, he was strongly encouraged to increase the pace
but was not stopped if he was able to keep swimming at least
with the CV200–400 pace. The time to cover each repetition
and the corresponding interval duration were recorded by an
experienced time-keeper using a digital chronograph (Casio,
HS 1000, Japan).
A finger-tip blood sample was taken at rest and every 400m for the determination of lactate concentration (Accutrend
Lactate, Hoffmann-La Roche Ltd., Basel, Switzerland). The
interval duration after the second, fourth, and eighth repetition on the 10 × 200-m and the fourth, eighth, twelfth and
sixteenth repetition on the 20 × 100-m were slightly extended
(20–30 s) for blood sampling. Heart rate was recorded continuously in each trial (Polar S810i). The time to complete
3 stroke cycles (T3) was recorded every second 50-m split
and was used to calculate the stroke rate (SR = 180·T3−1 ).
Stroke length (SL) was calculated from swimming velocity (V) and stroke rate (SL = V·SR−1 ). The mean SR and
SL of each 400-m in each set were used for comparison. The rate of whole body perceived exertion (RPE) was
recorded every 400-m using a 10-point scale.13 All tests
were performed in a 50-m outdoor swimming pool with a
water temperature of 26–27 ◦ C and 5 min after a warm-up
typically used before a training session (800 m easy selfpaced swimming at intensity below 150 b min−1 , 4 × 50 m
progressively increasing intensity). Two days before each
experimental condition the same low intensity and volume
of training was applied. The swimmers recorded their nutrition two days before the first experimental condition and
followed the same diet before each subsequent condition.
All tests were conducted during the same time of the day
(±1 h).
The average velocity, SR and SL of each 400-m repetition
were used in the statistical analysis. Normal distribution of
the data was tested using the Kolmogorov–Smirnov test and
sphericity was verified by the Mauchly’s test. A Two-way
analysis of variance for repeated measures on both factors (3
training sets × repetitions) was used for the statistical analysis of blood lactate, heart rate and stroke parameters (SR
and SL). One-way analysis of variance for repeated measures was used for the comparison of the average velocity
in each training set with CV4 and CV200–400 . The Tukey
post hoc test was used to locate possible differences between
A.G. Toubekis et al. / Journal of Science and Medicine in Sport 14 (2011) 363–368
365
Fig. 1. The mean velocity of each training set compared with the CV4 and CV200–400 velocities. The brackets over the bars indicate significant differences
(A). The velocity of each 400-m during the three training sets (5 × 400-m, 10 × 200-m, 20 × 100-m) compared with the CV4 and CV200–400 (B). The CV4
and CV200–400 velocities are indicated by the thick discontinuous lines. * p < 0.05, 5 × 400-m compared with CV4 and 5 × 400 compared with 20 × 100-m.
# p < 0.05, 20 × 100-m compared with the CV
200–400. The vertical lines 1, 2, 3 indicate the standard deviation of the 5 × 400, 10 × 200, 20 × 100 training sets
and lines 4, 5 the standard deviation of CV4 and CV200–400. All values are mean ± SD.
means. Effect size (ES) for differences between conditions
was calculated as described by Rhea14 and statistical Power
(P) of analysis was computed using the SPSS statistical
package. The Pearson correlation coefficient was used for
the correlation between variables and the level of significance was set at p < 0.05. The results are presented as
mean ± SD.
3. Results
The duration of swimming was longer during the
5 × 400-m compared to the 10 × 200-m and 20 × 100-m
(26.3 ± 1.3 vs. 25.8 ± 2.0 and 25.3 ± 1.7 min, p < 0.05)
and the total interval time was different between conditions (5 × 400-m: 2.6 ± 0.1 vs. 10 × 200-m: 2.9 ± 0.2
vs. 20 × 100-m: 3.0 ± 0.2 min, p < 0.05). However, the
summary of swimming time plus the interval, including
the additional time to complete the five blood samplings,
was similar between conditions (5 × 400-m: 29.6 ± 1.6,
10 × 200-m: 29.3 ± 2.2, 20 × 100-m: 29.5 ± 1.9 min,
p > 0.05).
The mean swimming velocity of the 5 × 400-m was lower
compared to CV4 (96 ± 2% of the CV4 ; ES = 0.64, P = 1,
p < 0.05). Velocities during the 10 × 200-m and 20 × 100-m
were similar and no different compared to CV4 (98 ± 2% and
100 ± 3% of CV4 ; ES = 0.29, p > 0.05). CV200–400 was lower
compared to CV4 and 20 × 100-m but no different compared
to 5 × 400-m and 10 × 200-m training sets (ES = 0.54, P = 1,
p < 0.05; Fig. 1A, p < 0.05). The mean velocity during the
5 × 400-m, 10 × 200-m, and 20 × 100-m training sets corresponded to 99 ± 3%, 102 ± 3, 103 ± 4% of the CV200–400 .
Swimming velocity was maintained constant within each
set of repetitions (p > 0.05) but was slower in each 400m repetition of the 5 × 400-m compared to CV4 and to
20 × 100-m (Fig. 1B, p < 0.05). The velocity of the repetitions five to twelve in the 20 × 100-m set was faster compared
to CV200–400 (Fig. 1B, p < 0.05). The CV4 , CV200–400 and the
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A.G. Toubekis et al. / Journal of Science and Medicine in Sport 14 (2011) 363–368
Fig. 2. Blood lactate concentration during the training sets of 5 × 400-m,
10 × 200-m and 20 × 100-m repetitions. * p < 0.05 compared to the first 400m. All values are mean ± SD.
5 × 400-m, 10 × 200-m, 20 × 100-m velocities corresponded
to 97 ± 1, 93 ± 2, 93 ± 2, 95 ± 2, 97 ± 2% of the 400-m
velocity respectively (1.37 ± 0.09 m s−1 ).
The blood lactate concentration was not different
between conditions (p > 0.05). Pooled data from all three
conditions showed that blood lactate concentration was
increased after 1200-m compared to 400-m (4.45 ± 1.1 vs.
5.82 ± 1.3 mmol l−1 , ES = 1.02, p < 0.05, Fig. 2). Blood sampling at 800-m was completed at approximately the 12th
min during the training sets and was no different with
blood lactate values measured at the 30th min of the training set (pooled data, 5.25 ± 1.13 vs. 6.24 ± 1.13 mmol l−1 ,
ES = 0.87, p > 0.05). Inspection of the individual blood lactate responses showed that six swimmers in the 5 × 400-m
(ES = 1.25), three swimmers in the 10 × 200-m (ES = 0.39)
and five swimmers in the 20 × 100-m (ES = 0.85) increased
the lactate concentration more than one mmol l−1 between
800 and 2000-m (between 12th and 30th min). Heart
rate during swimming was similar between conditions
(188–192 b min−1 , p > 0.05) but lower in the 5 × 400-m compared to 10 × 200-m and 20 × 100-m conditions during the
recovery periods (p < 0.05, Table 1). No differences were
observed on SR and SL across conditions and repetitions
(p > 0.05, Table 1). The RPE was no different between conditions but was increased significantly after 1200-m compared
to 400-m (p < 0.05, Table 1). The 400-m time was related to
CV4 and CV200–400 (r = 0.99, r = 0.96, p < 0.05).
4. Discussion
The findings of the present study show that during a
training set of 5 × 400-m repetitions the swimmers cannot
maintain the velocity corresponding to critical velocity calculated by the distances of 50, 100, 200, 400 m (CV4 ). In
contrast, the critical velocity calculated from distances of 200
and 400-m (CV200–400 ) can be sustained during the same set
of repetitions. The CV4 can be sustained when using 100 or
200-m repetitions and applying a rest to swimming ratio of
1:8. Half of the swimmers showed increases on blood lactate concentration more than 1 mmol l−1 between min 12
and 30 in the 5 × 400-m and 20 × 100-m conditions while
maintaining SR and SL.
The ability to sustain a prescribed velocity is probably
attributed to the internal perception of the intensity of the
exercise. It has been reported that experienced swimmers may
freely choose a pace similar to the maximum lactate steady
state during a long duration effort (i.e. 2000-m).15 Swimmers
in the present study probably perceived the CV4 intensity as
non-sustainable for the 5 × 400-m repetitions selecting a pace
by 4% lower. This indirectly may imply that CV4 intensity
does not correspond to a metabolically steady state. In support to the present findings, the swimmers in previous studies
were able to sustain velocity 5% below CV for 49 min with
steady oxygen uptake and lactate responses (3–5 mmol l−1 )
during continuous and interval swimming.4,8 The duration
of each 400-m repetition was about 5–6 min. Exercise duration of 4–6 min compared to 1 min (6 × 4 and 4 × 6-min vs.
24 × 1-min), resulted in a higher VO2 and heart rate during interval running forcing the runners to adjust their pace
to a lower intensity.16 Similarly, swimmers increased their
velocity in the shorter distances of 24 × 100 vs. 6 × 400-m,
and even more with a longer rest interval when they were
asked to maintain a pace corresponding to a blood lactate
concentration of 4 mmol l−1 .9
In contrast to 5 × 400-m the velocity corresponding to
CV4 was sustained during the 20 × 100-m and 10 × 200-m
repetitions. It is likely that the 2% and 4% higher intensity
during 10 × 200-m and 20 × 100-m resulted in a faster but
similar increase in oxygen uptake in each repetition compared to 5 × 400-m17 which was perceived as sustainable
because of the shorter duration of each effort. It should not
be overlooked that the total swimming time was longer in
the 5 × 400-m and the total rest interval duration was longer
in the 10 × 200-m and 20 × 100-m conditions. Although the
rest interval duration does not seem to affect the sustained
velocity and physiological responses during 4-min running
bouts,18 the duration of exercise may affect the time required
to maintain a high percentage of VO2 max, increasing the
perception of effort in swimmers19 and runners during high
intensity intermittent exercise.16 It is interesting that swimmers in the present study adopted the pace from the first
repetition of each set. They are probably adapted in adjusting to steady physiological stress because they follow similar
interval sets during daily training. This is probably the result
of a progressively increasing but non-maximal perception
of effort (end-RPE values 7–8) at all training sets which
is in agreement with previous studies using similar interval
protocols.4,16,18 Therefore, the duration of each exercise bout
and the number of repetitions may dictate the pace selection.
A.G. Toubekis et al. / Journal of Science and Medicine in Sport 14 (2011) 363–368
367
Table 1
The rate of perceived exertion (RPE), stroke rate (SR), stroke length (SL) and heart rate at the start (start-HR) and the end (end-HR) of each 400-m segment
during the three experimental conditions. Mean values for each 400-m distance (mean ± SD).
Distance of the training set (m)
RPE
SR (cycles min−1 )
SL (m cycle−1 )
Start-HR (b min−1 )
End-HR (b min−1 )
a
b
c
d
Training set
400
5 × 400-m
10 × 200-m
20 × 100-m
5 × 400-m
10 × 200-m
20 × 100-m
5 × 400-m
10 × 200-m
20 × 100-m
5 × 400-m
10 × 200-m
20 × 100-m
5 × 400-m
10 × 200-m
20 × 100-m
3.2
3.5
3.2
38.6
39.3
39.8
1.98
1.96
1.99
87
101
91
180
188
182
800
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
0.6
0.5
0.8
3.7
2.3
2.2
0.21
0.18
0.13
16
12
13
9
10
10
4.3
5.4
4.1
39.9
40.5
40.3
1.92
1.94
1.99
105
144
143
187
191
190
1200
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
0.5
0.7
0.9
2.4
2.8
2.1
0.15
0.18
0.15
22a
11a,d
25a,d
13
11
9
5.6
6.0
5.6
39.8
40.5
40.5
1.92
1.93
1.97
131
141
155
190
189
189
1600
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
1.2a
0.9a
1.6a
2.4
2.8
2.8
0.16
0.18
0.14
30a
14a
13a
15
9
10
7.0
6.8
6.2
39.8
40.3
40.5
1.92
1.94
1.96
137
144
163
192
197
190
2000
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
1.8 a,b
1.4 a,b
1.5 a,b
2.6
2.8
2.7
0.16
0.17
0.14
16 a
25 a
33 a
15
10
15
8.0
8.1
7.6
40.2
40.5
40.4
1.90
1.93
1.97
135
152
164
189
196
190
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
1.7 a,b,c
1.9 a,b,c
1.6 a,b,c
2.4
2.5
2.7
0.16
0.17
0.15
28 a
13 a
16 a
16
8
9
p < 0.05 compared to 400-m.
p < 0.05 compared to 800-m.
p < 0.05 compared to 1200-m.
p < 0.05 compared to the corresponding distance on 5 × 400-m.
Knowledge concerning the location of the CV across
the exercise intensity domains would have helped us to
explain our findings. Despite recent efforts,4 this has not been
resolved while a main concern is the selection of appropriate
swimming distances for the calculation of CV. Several combinations of distances and number of all-out efforts ranged
from 50 to 2000 m have been used.2,4,6 Using CV for the
evaluation of the aerobic endurance, scientists should assure
the balance of several assumptions20 with a practical, time
saving and easily applicable in populous groups procedure.
Longer duration all-out efforts such as those used in previous
studies (i.e. 800, 2000 m; ∼10–30 min)4,6 may not adequately
motivate the young swimmers. In this case shorter distances
(50–400-m) may be used2,7,8 although the resulted CV4 may
correspond to a different intensity domain. Based on the
present results CV200–400 may be more appropriately used
for longer repetitions (i.e. n × 400-m), while the CV4 may
be more appropriately used for short distance repetitions (i.e.
n × 100-m) during interval swimming training. To extend this
observation it seems that CV4 and CV200–400 may not represent the same intensity, although they may be located within
the same intensity domain. It is likely that CV4 may be located
close to the upper limit, while CV200–400 may be located in
the lower limit of the severe domain. This information has
practical importance for coaches helping them in the interval
training planning for the improvement of aerobic endurance.
The blood lactate concentration was increased after 1200
compared to 400-m in all conditions without any further
changes. Despite no statistical differences in blood lactate
response after 800 compared to 2000-m the magnitude of the
effect size of the pooled values was notable (ES = 0.87) and
half of the swimmers showed increased blood lactate by more
than one mmol l−1 during the 5 × 400-m and the 20 × 100-
m conditions. A lower increase (ES = 0.39, 0.6 mmol l−1 )
was observed in the 10 × 200-m condition (Fig. 2). In a
previous study the average lactate response on 24 × 100-m,
12 × 200-m or 6 × 400-m training sets was similar despite the
differences in the rest interval duration (10 vs. 30 s) and the
sustained velocity by 1–3%.9 Despite similar blood lactate
values, the kinetics of other physiological parameters should
be examined during the exercise and these may be useful in
characterising the metabolic stress of the interval training.
Although such data are not available for swimmers, there is
evidence that running16,18 and cycling21 with exercise interval duration of 1–5 min and intensities ranging from 82 to
93% of the peak aerobic velocity or power, maintain steady
O2 uptake, blood pH and blood HCO3 .16,18,21 The intensity in the three experimental conditions in the present study
ranged from 93 to 97% of the 400-m velocity corresponding
to 96–100% of the CV4 and 99–103% of the CV200–400. The
running and cycling interval training protocols may not simulate those of swimming but it is likely that the young well
trained swimmers were able to adjust their pace at a given
distance or rest interval in order to avoid a severe metabolic
response, thus swimming in the sustainable heavy intensity
domain.
It is interesting to note the maintenance of stable SR and
SL in all conditions in the present study (Table 1). Maintenance of technical characteristics is important for young
swimmers and this was succeeded despite the high intensity of these sets. The present observation is in agreement
with previous findings during interval swimming.8 However,
a decrease of SL at a velocity corresponding to 87% of the
maximum aerobic speed,22 as well as in SR during intermittent swimming have been reported.7 It was possibly not
necessary for the swimmers in the present study to change
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A.G. Toubekis et al. / Journal of Science and Medicine in Sport 14 (2011) 363–368
their SR and SL since they were keeping the pace they felt
able to sustain. A substantial increase in SR and a reduction
of SL have been reported at velocities above the CV.22,23
Whatever the case, the maintenance of a stable SR and SL
indicate that no significant deterioration in technical parameters occurred during all three conditions. This implies that the
interval swims investigated in the present study are appropriate for the establishment of efficient swimming technique in
young swimmers and this should be considered by coaches.
5. Conclusion
Critical velocity can be effectively used for the design of
interval swimming training sets. The metabolic and stroke
mechanics responses during these sets indicate that they
can be used for the improvement of aerobic endurance.
Despite non-steady metabolic responses, repetitions of
distances of 100, 200 and 400-m can be used during interval
training with an exercise to rest ratio of 1:8. However,
appropriate adjustment of the swimming pace should be
applied according to the set distance and the distances used
for the calculation of CV.
Practical implications
• The findings of the present study suggest that the selection of distances to establish the distance–time relationship
and calculate the CV is important for the prescription of
swimming velocity during interval training.
• Selection of longer distances for the CV calculation (i.e.
200–400-m) may be more appropriate for the prescription
of pace in long distance repetitions (i.e. n × 400-m).
• The use of short combined with long distances for the CV
calculation (i.e. 50, 100, 200, 400-m) may help to define a
pace for interval training including repetitions of 100 and
200-m.
• The above highlights the practical importance of using CV
as a means to prescribe aerobic endurance training sets.
During interval aerobic endurance training when the distance of the repetitions is doubled, the velocity should be
reduced by 2% targeting to comparable heart rate and lactate responses. This means that the velocity of n × 400-m
repetitions should be 2% slower compared to the velocity of the n × 200-m repetitions, while a set of n × 100-m
repetitions should be 2% faster compared to the 200-m.
Acknowledgment
No external financial support was received for this work.
Appendix A. Supplementary data
Supplementary data associated with this article can
be found, in the online version, at doi:10.1016/j.jsams.
2011.03.002.
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