Biomechanics and Medicine in Swimming XI

BiomechanicsandmedicineinswimmingXi
Swimming and Respiratory Muscle Endurance
Training: A Case Study
lemaître, F., chavallard, F., chollet, d.
Centre d’Etudes des Transformations des Activités Physiques et Sportives
(CETAPS, EA3832), France
The aim of this case study was to investigate whether respiratory
muscle endurance training (RMET) would increase performance
in a long-distance swimmer. An expert long-distance
swimmer trained for 10 weeks in a RMET program (30 minutes
a day, 5 days a week) plus his usual swim training. Maximal swim
time trials, ventilatory function tests, maximal inspiratory and
expiratory pressure (MIP and MEP), and respiratory endurance
tests (RET) were done. Ventilatory function parameters were not
improved post-training, but MIP, MEP, RET and swimming
performance were increased (+19%, +33%, +7 minutes; 50 m:
-5.4%; 200 m: -7.2% respectively). RMET may be thus a useful
technique to improve performance in long-distance swimmers.
Key words: endurance, respiratory muscle, performance
IntroductIon
The aim of this case study was to investigate whether respiratory muscle
endurance training (RMET) would increase performance in a longdistance
swimmer. Immersion in water increases the pressure around the
thorax, raising ventilatory constraints both at rest and during physical effort.
Until lately, ventilation was not considered to be a limiting factor for
sub-maximal or maximal effort. However, it was shown that this ventilatory
limitation decreases maximal performance in healthy subjects and
athletes (Verges et al. 2007). It was thus suggested that training might
delay respiratory muscle fatigue and permit better distribution of blood
flow to the working muscles. It has often been observed that swimmers
have pulmonary volumes that are greater than both predicted values and
those of controls (Doherty et al., 1997). The improved pulmonary volumes
in swimmers could be due to swim training per se (Clanton et al.,
1987), stronger respiratory muscles (Doherty et al., 1997), alveolar hyperplasia
(Armour et al., 1993), or accelerated pulmonary growth (Courteix
et al., 1993). Clanton et al. (1987) showed that pulmonary function,
endurance and respiratory muscle force were improved after swim training,
whereas supplementary RMET did not lead to additional change.
Similarly, Wells et al. (2005) showed that swim training alone improved
pulmonary function and respiratory muscle force to the same extent as
RMT associated with swim training. These findings seemed to be confirmed
in a more recent study in high-level swimmers (Mickleborough et
al., 2008). Moreover, it was recently reported that the impact on swimming
performance seems to be limited (Kilding et al., 2009).
Methods
An expert long-distance swimmer (21 years, 183 cm, 71 kg) trained for
10 weeks in a RMET program plus his usual swim training. The athlete’s
speciality was the 1,500-m event and he was a finalist in the French
national championships. His best performance time on this distance
was thus expressed as a percentage of the current world record, and was
93.4%. He was not asthmatic and consented to the study requirements
in writing. The experimental procedures were conducted in accordance
with the Declaration of Helsinki and were approved by the local ethics
committee. He was evaluated on two occasions: before (1 week) and just
after the RMET program.
Measurements of body mass and skin folds were generally made between
8.00 and 10.00 A.M.; the swimmer presented after training in
a fasted state and all anthropometric parameters were measured by the
same investigator. Height was measured to the nearest 0.5 cm (Tanita,
206
Tanita Corp., Arlington Heights, IL, USA). Body composition (fat mass:
FM) was estimated with the skinfold method of Durnin and Womersley
(1974) using a calibrated skinfold calliper (Model HSK-BI, Baty International,
West Sussex, UK). Chest expansion was measured at the level
of the xiphoid process using a tape measure. The subject was instructed
to perform a maximal exhalation [to residual volume (RV)] and then
an inhalation to maximum inspiratory capacity (MIC). Chest expansion
was calculated as the difference between circumferences at RV and MIC.
The CV of test-retest measurements (within the day) at the level of the
xiphoid process was 0.7%. Buoyancy was evaluated by measuring the hydrostatic
lift (HL), which is the force that enables swimmers to float
when they are immersed in forced inspiration. It was measured at the end
of a maximal inspiration when the subject was floating. The subject was
in the fetal position, facing downward. A lead mass (0.1-1 kg) was placed
on the swimmer’s back between the shoulder blades. The load needed to
keep the subject just under the water was taken as the HL. For the glide
distance measurement, the subject was asked to adopt a prone position
with the arms completely extended at the elbows and wrists, to position
the upper arms in contact with the sides of the head (one hand on top of
the other), to maintain the feet together with the ankles plantar flexed,
to hold onto the wire, and to hold his breath after a maximal inspiration.
For the passive torque time (Tt), which can be defined as the time it
takes for the body to pass from horizontal to vertical position, the same
researcher maintained the swimmer in the horizontal position until a
signal was given by another researcher, who then noted the time it took
for the swimmer to get into vertical position. The subject was asked to
hold his breath after a maximal inspiration until the test ended. Each
time (before and after RMET), three glide and three Tt measures are
made in order to calculate and average the glide distance.
Several parameters were measured for the pulmonary function tests:
forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1),
and peak expiratory flow (PEF). For each parameter, the best value was
chosen from at least three consecutive maneuvers differing by no more
than 5% (Quanjer et al. 1993). All parameters were measured with a Microquark
spirometer (Cosmed, Rome, Italy) in the same conditions, with
the subject in a sitting position and breathing through the mouthpiece
with a nose-clip. The spirometer volume was calibrated twice daily with
a 3-L calibrated syringe. The results were corrected to BTPS conditions
and compared with predicted values (Quanjer et al. 1993). The maximal
inspiratory and expiratory pressures (MIP and MEP) were measured
in the sitting position at the end of a normal expiration and inspiration
(MEPFRC, MIPFRC) using a small portable mouth pressure meter
(ZAN 100 USB, ZAN Messgeräte GmbH, Germany). The subject was
verbally encouraged to achieve maximal strength. All maneuvers were
repeated at least twice.
The respiratory endurance test (RET) was performed with the
SpiroTiger® device. The subject was asked to sustain a given minute
ventilation (VE) with a predetermined tidal volume (VT) and respiratory
frequency (fR) for as long as possible; that is, until he could no
longer sustain either VT or fR despite three consecutive “warnings” by
the experimenter. The RMET was performed 30 minutes a day, 5 days
a week, with the same specific device (SpiroTiger®) allowing partial rebreathing
of CO2 and thus assuring normocapnic hyperpnea. RMET
consisted of voluntary normocapnic hyperpnea at a given VT and fR
with a duty cycle of 0.5. The Spirotiger® provided breath-by-breath
feedback of fR and VT. The size of the re-breathing bag was set at 50-
60% of vital capacity, and VE of the first training session was set at 60%
of the maximal voluntary ventilation. The swimmer was instructed to
increase fR after 25 min of training, if he felt he would not be exhausted
by 30 min. If he felt he could not sustain the target for 30 min, he was
to decrease the fR. The swimmer was instructed to increase fR from
one session to the next by 1-2 breaths/min and was monitored by the
experimenter at least once a week to verify compliance.
The swimming performance was evaluated from the 50-m and 200m
time trials (TT50m and TT200m) swum at maximal velocity and in