Blood lactate responses during water-based lifesaving tests
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JEPonline
Journal of Exercise Physiologyonline
Official Journal of The American
Society of Exercise Physiologists (ASEP)
ISSN 1097-9751
An International Electronic Journal
Volume 5 Number 1 February 2002
Sports Physiology
BLOOD LACTATE LEVELS DURING A COMBINED WATER-BASED EXERCISE
TEST IN ELITE LIFESAVING ATHLETES
V. ALFARO, L. PALACIOS, AND R. TORRAS
Department of Physiology, Faculty of Biology, University of Barcelona, E-08028 Barcelona, Spain.
ABSTRACT
BLOOD LACTATE LEVELS DURING A COMBINED WATER-BASED EXERCISE TEST IN ELITE
LIFESAVING ATHLETES. V. Alfaro, L. Palacios, R. Torras. JEPonline. 2002;5(1):1-4. Blood lactate
(La) levels were analysed during a combined exercise test in elite lifesaving athletes, which included 50 m
freestyle swimming at maximal effort, 15-20 m underwater swimming, and 30 m dragging of a mannequin
simulating a drowned person. Swimming resulted in increased blood La to a level close the onset of blood La
accumulation (3.60.9 and 4.61.4 mmol/L for men and women, respectively). However, after further
underwater swimming blood La did not increase significantly. Finally, after the completion of the combined
test higher blood La values (12.72.5 and 11.62.7 mmol/L for men and women, respectively) were found.
These findings suggest that during the intermediate phase of underwater swimming the duration was short
enough, and the exercise intensity low enough, for the energy required to be obtained from aerobic sources.
Nevertheless, a transient hypercapnia may have occurred, causing the retention of La in the intracellular
compartment. However, increased ventilation in the last part of the test in addition to a strong anaerobic effort
when dragging the mannequin may lead to the higher La values found at the completion of the trial. More
research is required of the metabolic and physiological demands of lifesaving.
Key Words: Performance, Physical Fitness, Hypercapnia, Hypoxia
INTRODUCTION
Several studies have been performed on adaptation to exercise in athletes during the performance of different
aquatic sports, including swimming (1), swimming during triathlon races (2), synchronized swimming (3),
breath-hold diving (4) and water polo (5). However, to our knowledge no information has been provided about
blood lactate levels during the exercise tests usually performed by elite lifesaving athletes. In competitive
lifesaving, the contestants are required to perform different series of exercise trials, but the most characteristic
of this peculiar sport is a combined test that includes consecutive bouts of swimming, underwater swimming
and dragging of a mannequin. Lifesaving is a sport in which increased metabolic demands are required in a
short-term, always less than 2 minutes. Indeed, this combined test is the trial that best reflects the work
involved in emergency lifesaving
Blood lactate responses during water-based lifesaving tests
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The aim of the present study was to examine the changes in blood lactate (La) levels in elite lifesaving athletes
during the combined exercise test. As blood La determination is a tool routinely used in the science of
coaching, the present data may be of help in designing training programs for lifesaving athletes.
METHODS
The subjects who volunteered for this study were five men and five women from the Spanish Lifesaving Team
and the analyses were performed during the 1994 European Lifesaving Championship. The characteristics of
the subjects are presented in Table 1. All tests were performed under close clinical supervision, and the subjects
were fully informed of the purpose of this study and possible risks before signing the informed consent form in
accordance with the recommendations of the Declaration of Helsinki.
Table 1. Subject characteristics.
The trials were performed in a 25 m indoor
swimming pool. The water temperature during
Variable
Men
Women
the experiments was approximately 28°C. The
Age (yrs)
19±2
20±3
combined exercise test for lifesaving athletes
consisted of a 50 m freestyle swimming trial at
Height (cm)
178.8±2.9
169.4±4.6
maximal effort (part 1), plus 20 m underwater
Body weight (kg)
73.0±7.8
73.0±8.4
swimming (15 m for women) to reach a
mannequin. The mannequin is made of PVC,
Maximal work load (W)
333±20
268±26
with a higher density than that of water (1.3
VO2 max (mL/kg/min)
61.2±6.1
54.1±5.9
g/cm3, 60 kg), and is positioned on the bottom
of the swimming pool (2.5 m deep) simulating
AT (% VO2 max)
82.6±7.3
74.7±13.7
the drowned person (part 2). The third and
final stage of the test requires that the
mannequin be held and dragged for 30 m (35 m for women), always keeping the head of the mannequin out of
the water (part 3). These three parts are usually performed without interruption. However, due to the
impossibility of withdrawing blood samples without stopping the exercise, a protocol was designed in which
samples were taken at the end of each part. Thus, athletes performed in different series part 1, part 1 plus part 2,
and finally part 1, 2 and 3. Time records were accounted to check their reproducibility. A resting period of more
than 2 hr occurred between each series.
Baseline La measurements were taken prior to the beginning of each phase to check an adequate recovery (6).
Blood samples (20 l) were taken from the earlobe 3 and 5 min after each test. The samples were pipetted into
chilled tubes containing 0.6 N perchloric acid solution and centrifuged. Blood samples were analysed as
previously described (7). Statistical significance was assessed using an analysis of variance (ANOVA) with
repeated measures. The Student-Newman-Keuls test was performed for post-hoc analyses. Results were
considered significant at the p<0.05 level, and data are expressed as means±SD.
RESULTS
Time records between series were uniform and reproducible. Mean velocities and time records for the three
parts of the combined test are shown in Table 2. These data reflected that both underwater swimming and
further dragging of the mannequin decelerated the athletes with respect to the first part of the test. Figure 1
shows the blood La levels found during the combined exercise test. Blood La concentration measured after the
first 50 m of swimming (part 1) was not significantly different from that measured after 50 m swimming and
further 15-20 m underwater swimming (part 1 plus part 2). However, the blood La concentration after the inwater mannequin drag was notably higher.
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Blood lactate responses during water-based lifesaving tests
Table 2. Time and velocities of performance for parts of the combined test.
Part 1
Men
Women
Part 2
Part 3
s
v, m/s
s
v, m/s
min’s
v, m/s
29.34±1.57
32.95±2.20
1.704±0.032
1.517±0.046
47.31±0.56
49.00±2.54
1.479±0.025
1.326±0.043
1'16.27 ±1.10
1'30.08 ±1.09
1.311±0.024
1.110±0.027
DISCUSSION
The mean velocities found during the first 50 m of freestyle
swimming in lifesaving athletes were similar to the mean
velocity found in other studies on swimming (1,5). Blood
La values found in this first part of the combined test were
around the onset of blood lactate accumulation (OBLA, 4
mmol/L). Diverse investigators have used the OBLA as a
useful and important index for estimating the swimming
endurance performance. Thus, the exercise intensity
corresponding to OBLA has been used as the optimum
swimming training intensity (8-10). However, an
unexpected finding was that after additional 15-20 m of
underwater swimming blood La levels did not significantly
change. This means that the energy required during the
intermediate phase could be obtained from aerobic sources,
which may be favoured first by the decrease in the exercise
intensity during underwater swimming, and second by
improved O2 release to the tissue on this condition (11)
Nevertheless, lactate retention in the muscular
compartment during this intermediate part of the combined
test should not be disregarded. Indeed, significant
hypercapnia has been found in synchronised swimmers (3)
and rats (12) during short periods of underwater
swimming. Blood La is decreased at high workloads after Figure 1: Blood La concentration in men (n=5) and
inhalation of hypercapnic gas mixtures simulating women (n=5) elite lifesaving athletes during the
respiratory acidosis (13). This La decrease in blood has performance of a combined exercise test which
been attributed both to a direct effect on intracellular pH consisted in 3 parts performed in a continuous way.
Part 1: 50 m freestyle swimming trial at maximal
and the regulation of key glycolytic enzymes and/or the effort; Part 2: 20 m underwater swimming (15 m
influence of extracellular pH on the release of La from for women) to reach a mannequin deposited on the
intra- to extracellular fluid (13). In the present study, bottom of the swimming pool (2.5 m deep)
although not evaluated, the underwater swimming during simulating the drowned person, and Part 3: holding
and dragging of the mannequin to complete 30 m
part 2 was an intermediate phase of exercise with apnoea. isometric swimming. Red circles: La after 3 min
Consequently, the apnoea together with the CO2 generated stopping exercise; blue circles: La after 5 min
by proton buffering from the metabolic acidosis incurred stopping exercise. *=significantly different from
during the initial 50 m swimming may contribute to Part 1 La values (p<0.05)
increase the blood PCO2. However, hypercapnia may be
reduced in the part 3 of the combined test by increased
ventilation. Therefore, a transient respiratory acidosis developed during underwater swimming in the
intermediate part of the combined test may contribute to the retention of La in the intracellular compartment,
but La efflux from intra- to extracellular compartment would increase in the last part of the combined test.
Blood lactate responses during water-based lifesaving tests
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Finally, significant increases in blood La concentration were found at the completion of the third part. Thus, the
dragging of the mannequin simulating the drowned person was an intense task, requiring an increased
dependence on anaerobic metabolism.
In conclusion, the present study provides evidence of the extent to which an important anaerobic component
may be present in these characteristic trials. Thus, we believe that the present data may be of use in the training
of lifesaving athletes.
ACKNOWLEDGEMENTS
This study has been supported by a grant (PB93-0740) from the Spanish National Programme for Scientific
Research and Technological Development. The authors are grateful to Mr. Robin Rycroft for English edition.
We wish also to thank the Spanish Lifesaving Federation for the facilities provided, especially to the team
coach and the national selector.
Address for correspondence: Dr. V. ALFARO, Departamento de Fisiología, Facultad de Biología
Universidad de Barcelona, Avda. Diagonal, 645 E-08028 BARCELONA (SPAIN); Phone: 34-93-4021526
Fax: 34-93-4110358; E-mail: valfaro@bio.ub.es
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