An extensive review of the literature revealed that
the present study was the first to use two markers for
assessment of asthma improvement – BHR measurement
and spirometric parameters – in a group of MPAA patients
subjected to swim training compared with a control group
of asthmatic non-swimmers.
Several authors have shown that aerobic exercise and
training improve physical fitness.3,8-12,24-27 On the other
hand, although swimming is the best choice of physical
activity for people with asthma, few randomized controlled
trials with medium- to long-term follow-up have been
conducted to assess its effects in the various degrees of
asthma severity.
After the treatment period, both groups showed
improvement in spirometric parameters, although the
difference did not reach statistical significance. There was
also significant improvement in BHR, with higher values in
the swimming group.
The mechanisms underlying this significant improvement
in BHR and improvement in lung function upon comparison
of the swimming and control groups probably involve
changes in airway inflammation, mechanical, neurogenic,
and humoral factors, and smooth muscle changes,28 but
this remains to be proved. Recent studies have shown
encouraging results on the effects of physical exercise in
decreasing BHR.17,28 Shaaban et al.17 reported a strong
negative correlation between physical activity and BHR in
adults. If this relationship is indeed a causal one, these
results suggest that a small amount of physical activity
is able to effect a significant reduction in BHR; this could
then be added to the growing list of already-known benefits
of exercise. Using an experimental model of asthma, an
intriguing study by Silva et al.28 showed that physical
training can reverse airway inflammation and remodeling
and improve respiratory mechanics, consequently reducing
BHR.28 If confirmed, these encouraging results could
contribute to the development of programs for the primary
prevention of lung disease.
In our review of the Brazilian literature, we were unable to
find any studies that assessed bronchial hyperresponsiveness
with methacholine challenge test after swimming. This fact
was addressed at length in a Thorax editorial25 commenting
on a study by Matsumoto et al.3, which assessed BHR to
histamine in 16 patients with severe asthma (8 swimmers
and 8 non-swimmer) before intervention and at 6-week
follow-up. There was no difference in BHR between the
two groups before or after swim training. It bears stressing
that the Matsumoto study included only a small number of
severely asthmatic patients who did not follow the same
medication regimen, whereas our study included a greater
number of participants, all of whom received adequate and
standardized treatment.
The increase in PC20, which was significantly greater
in the swimming group, suggests a need for further, longterm
studies of swim training that include assessment of
markers of inflammation, cardiorespiratory function, and
clinical improvement of asthma, as well as quality of life
questionnaires.
While some studies have shown beneficial effects of
swimming on pulmonary function test parameters,11,15
others have failed to show any such effect.3,10,13,29 However,
none of these studies used BHR assessment as a followup
tool. BHR must be assessed, especially in studies that
evaluate response to asthma treatment over time.30
Three issues stand out in most articles on the matter
indexed in major databases: small, uncalculated sample
size; absence of a control group; and very short duration
of swim training. The present study, which was designed
with a group of MPAA patients in mind, had a predefined
and properly calculated sample size, had a control group,
and used standardized pharmacological treatment of asthma
and swimming exercises across all participants. Fitch et al.24
reported great improvement in asthma symptoms after one
year of swim training, even though no improvement in BHR
or pulmonary function tests was observed.
In the present study, we found significant improvement in
FVC and FEV1 in both groups, and confirmed the efficacy of
inhaled corticosteroids as a standard treatment for childhood
asthma. The difference in BHR reduction between groups,
as measured by increased PC20 values, shows the efficacy of
swimming. Improvement in MIP and MEP values shows that
swimming also proved useful for improving the respiratory
mechanics of children and adolescents with asthma. Other
controlled trial may corroborate these findings.
Regarding spirometric parameters, one possible limiting
factor in our study was the fact that children were still in
the early stages of the swimming program. This may have
limited improvement in cardiorespiratory fitness and had an
even greater influence on results. Only four of the children
in our sample had previously engaged in swimming.
Welsh et al.29 suggest that regular physical activity, when
in conjunction with adherence to proper pharmacological
treatment, should be encouraged by physicians and other
health professionals to all children and adolescents with
asthma. Immediate benefits can be derived from engaging
in physical activity, particularly increased expiratory reserve
capacity, which may provide protection against asthma
attacks.In spite of recent evidence suggesting that chlorine
exposure during swimming may be associated with an
increase in the frequency of asthma attacks,31,32 there is
considerable evidence1 that swimming in a heated indoor
pool environment, which provides warm, moist air for
inhalation, is still far less asthmogenic than other types of
exercise, such as running or cycling.2 The harmful effects
of chlorine appear to be dependent on concentration and
length of exposure, and still require further study.2,14
A 2009 study by Bemanian et al.15 showed significant
improvement in peak expiratory flow rates in asthmatics
after swimming, and suggested that indoor swimming is
useful for patients with asthma, regardless of the potentially
toxic effects of chlorine.Research has shown airway irritation and BHR changes in
competitive swimmers, who regularly attend heated indoor
pools with high water and air levels of chlorinated compounds
(particularly NCl3). 29 This was demonstrated in a study by
Thickett et al.33 and warranted an editorial on the matter.34
The pool facility in which our patients trained did not have
completely enclosed walls near the roof; we are unsure
as to whether this may have decreased the concentration
of chloramines in the air. This factor set our study apart
from those conducted in Europe, where indoor swimming
facilities are completely enclosed due to the harsh winter. The
findings of these studies have prompted encouragement of
unchlorinated pools or increased ventilation in pool facilities.
Future studies to measure the concentration of chloramines
in the air of swimming facilities are thus required.
Swimming has been recommended in asthmatics because
it is associated with less exercise-induced bronchospasm
(EIB) than are other types of exercise. This has been
proven by several authors. The mechanisms behind this
protective effect have yet to be fully elucidated. They
probably inclide epithelial, cellular, or sensorineural factors
in a moist environment, as EIB does not appear to be an
issue in asthmatic swimmers. None of the participants in
our sample experienced asthma attacks during swimming
or in the first few hours after swimming.
Our results show that three months of swim training (at
adequately ventilated pools) leads to significant reduction in
bronchial hyperresponsiveness and improves elastic recoil
of the chest wall in children and adolescents with moderate
asthma and atopy. Swimming should therefore be one of the
sporting activities encouraged in children with MPAA.
Other well-designed studies that address the important
issue of physical training programs as a tool for improved
asthma control and must be encouraged.