the prevalence of asthma among finnish competitive swimmers is higher than that in general population which is typical in endurance sports [ 1 , 2 ] .
asthma and especially the nonallergic asthma were more prevalent in women than men [ 3 , 4 ] .
in finnish general population asthma was mostly associated with family history of asthma , allergy , smoking , and obesity .
general population is different than competitive swimmers population , because weight gaining , aging , and smoking - related factors are missing as competitive swimmers are mainly fairly young , with normal bmi and nonsmoking .  
intensity , duration , and type of exercise are known to have an effect on the severity of the respiratory symptoms .
for example , at the same exercise intensity level , asthmatic symptoms are fewer and milder in swimming than in running or cycling [ 6 , 7 ] . that may affect the selection of sport in persons who have sensitivity in lung function . in all endurance sports like swimming as well ,
.   in asthmatics physical exercise in the intensity level of 90% of maximum heart rate for 68 minutes typically causes the asthmatic symptoms . in a previous study by pivinen et al .
to our knowledge the gender differences in asthmatic symptoms in different intensities in swimmers with physician - diagnosed asthma are not studied before .
the aim of the study was to examine gender differences among competitive swimmers and especially swimmers with asthma .
the focus was to concentrate on comparing allergies , family history of asthma and allergies , and the respiratory symptoms in different intensities in physical exercise between female and male swimmers .
as swimming has been suggested to be a suitable physical exercise therapy for persons with asthma , this study examined swimming special features related to asthma and allergy to obtain further knowledge of the differences between female and male swimmers .
three hundred finnish competitive swimmers , 156 females and 144 males , were studied by a questionnaire .
studied swimmers were selected for the study according to the sufficient training history and performance level of qualification for national championships .
swimmers were at mean sd age of ( mean sd ) 18  3 years , females 17  3 and males 19  3 years .
swimming training history was mean 7  2 years in females and 7  3 years in males .
weekly training hours were on the average 16  4 hours in females and 16  3 hours in males .  
gender differences of prevalence of physician - diagnosed asthma , allergy , and respiratory symptoms were studied first .
the differences were studied with the chi - square test and considered significant when p value was < 0.05 .
wilcoxon sum rank test was used to compare the ages of the onset of asthma diagnosis in asthmatic swimmers .
the questionnaire consisted of questions concerning basic information , training history , asthma , allergy , family history of asthma and allergy , and respiratory symptoms ( shortness of breath , wheezing , coughing , and mucous production ) during swimming .
five ( i  v ) different swimming intensities as presented , for example , by keskinen 1993   were recorded .
intensity zone i represented easy endurance swimming , zone ii was moderate endurance exercise between aerobic and anaerobic thresholds , zone iii was a swimming pace between the anaerobic threshold and the minimal velocity to achieve maximal oxygen uptake , zone iv velocity was higher than zone iii , with a competition - specific race pace maximizing muscle lactic acid production , and zone v was all - out sprinting .
the questionnaire has been applied earlier for swimmers .   in asthmatic swimmers , physician - diagnosed allergy , family history of asthma and allergy , and
the analysis describing symptoms in five different training intensities was previously used by leynaert et al .
asthmatic symptoms wheezing , coughing , shortness of breath , and mucous production during swimming at five ( i  v ) different exercise intensities .  
the ethics committee of the hospital district of helsinki and uusimaa approved the study protocol .
no gender differences in prevalence of physician - diagnosed asthma and reported respiratory symptoms were found .
male swimmers reported significantly more physician - diagnosed allergy ( p = 0.007 ) than females .
no gender differences were found when reporting respiratory symptoms in swimming in the whole 300 swimmers population ( figure 1 ) .  
however among swimmers with asthma , gender differences were found in the age of onset of asthma , when reporting respiratory symptoms , and in the family history of asthma ( table 1 ) .
no gender differences were found in allergies in swimmers with physician - diagnosed asthma ( table 2 ) .   in swimmers with asthma ,
gender difference was observed as females reported more symptoms at the intensity ii : moderate endurance training ( figure 2 ) .
female swimmers with asthma reported significantly more coughing and mucous production at moderate swimming intensity .
in addition female swimmers with asthma reported significantly more coughing in every intensity level than male swimmers with asthma ( table 4 ) .
among the studied 300 swimmers , no gender difference in prevalence of asthma was found , unlike in the previous studies in finnish general population .
athletes with asthma may choose swimming because it is a low asthmogenic sport [ 6 , 7 ] , and in spite of asthma many athletes may achieve international top level .
the studied competitive swimmers had normal weight and were nonsmoking young adults , so the reasons mostly related to gender differences in general population in females were excluded : obesity and hormonal changes in the age of 4060 .  
that may be linked to the fact that swimming is a low - symptom - causing sport and therefore especially chosen by males with allergy . in swimmers with asthma no gender differences in reported physician - diagnosed allergy were found . that was inconsistent with previous studies on general population where nonallergic asthma was found more in females . among swimmers with asthma gender difference was significant in the age of the onset of asthma ( table 1 ) as male swimmers had asthma in younger age than females .
results show that male swimmers mainly had asthma before swimming training had started and females later during swimming career , almost in puberty .
therefore , fewer cases having family history of asthma and later onset of asthma may be related to higher amount of reported respiratory symptoms during swimming in asthmatic female swimmers . in previous studies [ 2 , 9 ] family history of asthma and allergies
also in this study only two of 57 swimmers with asthma ( 0.07% of 300 studied swimmers ) reported asthma without any allergy or family history of asthma .  
gender differences in swimmers with physician - diagnosed asthma were found in reported respiratory symptoms during swimming .
interestingly , coughing , which in previous studies has been reported to be the most common respiratory symptom in athletes [ 5 , 13 ] , was frequently reported in asthmatic female swimmers but not in males . in a study by heir ( 1994 )   all but coughing was more frequent in athletes with asthma , which is consistent with the result in this study on asthmatic male swimmers .
the results showed , surprisingly , that female swimmers with asthma reported significantly more often symptoms in moderate intensity than males ( figure 2 and table 4 ) .
this observation may have been linked to the asthma background as the females had their asthma diagnosis mainly during swimming career .
it may also be influenced by smaller lungs related to body size in females than males .
this may also cause gender difference in the ventilation dynamics during swimming and the efficiency in body - size - related work load in physical exercise on land . with different ventilation dynamics in females and males ,
according to asthma allergy and respiratory symptoms gender differences in competitive swimmers vary from general population . in swimmers with physician - diagnosed asthma gender differences
 
 background and aim . 
 asthma is common in endurance athletes including swimmers . our aim was to study gender differences in asthma , allergy , and asthmatic symptoms in swimmers and investigate the effects of varying intensities of physical exercise on competitive swimmers with asthma . 
 methods . 
 three hundred highly trained swimmers ( 156 females and 144 males ) were studied by a questionnaire . 
 their mean ( sd ) ages were 17  3 and 19  3 years , and they had training history of 7  2 and 7  3 years in females and males , respectively . 
 gender differences in asthma , allergy , and respiratory symptoms were examined . 
 special attention was focused on asthmatic swimmers , their allergies and respiratory symptoms during swimming at different intensities . 
 results . 
 the prevalence of physician - diagnosed asthma was 19% for females and males . 
 no gender differences in asthma or respiratory symptoms were found . 
 males reported allergies significantly more often than females ( p = 0.007 ) . 
 gender difference was found in respiratory symptoms among swimmers with physician - diagnosed asthma because females reported symptoms significantly more often ( p = 0.017 ) than males . 
 asthmatic females also reported symptoms significantly more often at moderate intensity swimming ( p = 0.003 ) than males especially for coughing . 
 discussion . 
 gender difference in prevalence of asthma was not found in swimmers . 
 however , allergy was reported significantly more by male swimmers . 
 male swimmers with asthma reported significantly more cases having family history of asthma , which may be a sign of selection of asthma - friendly sport . 
 moderate intensity swimming seemed to induce significantly more symptoms especially coughing in asthmatic females . 
1. Introduction
2. Methods
3. Results
4. Discussion
5. Conclusions