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Original Research

Incidence of Exercise-Induced Asthma in Adolescent Athletes under Different Training and Environmental Conditions

Sidiropoulou, Maria P.; Kokaridas, Dimitrios G.; Giagazoglou, Paraskevi F.; Karadonas, Michalis I.; Fotiadou, Eleni G.

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Journal of Strength and Conditioning Research: June 2012 - Volume 26 - Issue 6 - p 1644-1650
doi: 10.1519/JSC.0b013e318234eb0c
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Abstract

Introduction

A frequent triggering factor of asthmatic episodes even in the case of individuals who exercise regularly is the stimulus of exercise itself or its sudden interruption (16). In fact, many individuals, especially children, exhibit bronchial reaction to exercise without any history of asthma or other symptoms, with exercise-induced bronchospasm (EIB) as the sole manifestation (23).

Prompt diagnosis of exercise-induced asthma (EIA) is of great importance in the case of children and young adults exercising in school and sport settings, because the occurrence of dyspnea, shortness of breath, and chest tightness symptoms during exercise is usually attributed to poor levels of physical condition instead of the true underlying cause, which in turn results in the lack of treatment and problem maintenance (6,16,19). In fact, studies have shown that certain environmental conditions related to temperature and humidity conditions according to sport can affect EIA occurrence (8,9,11,13,30). On the other hand, although physical activity can generate EIA incidence, it also constitutes one of the most effective ways of confronting such conditions because improvement of physical condition through exercise helps each individual to tolerate stimulus of exercise and increase his or her defense against breathing difficulty symptoms (16,30).

Diagnosis of EIA is achieved by surveying the history and conducting test trials, and this includes either the free running test or treadmill and cycle ergometer use in laboratory settings. In general, the free running test is considered as a reliable and validated test for the diagnosis and evaluation of lung function and all related factors that can generate EIA, such as air humidity and temperature along with the type, intensity, duration, and training method used (16,31). An advantage of the free running test is that when performed at a submaximal intensity equal to 80–90% of the maximum heart rate (MHR) for a duration of 6–8 minutes, it has the ability to induce EIB even if the laboratory results are negative (6,9,20). Furthermore, the free running test constitutes a natural way to exercise that is equally valued as much as running during physical education (PE) activities in school settings; thus, it is more acceptable by parents and children (18,21).

As regards sports, it is known that the competitive nature of team sports such as football, basketball, and water polo that require fast interchanges between offense and defense often leads participants to overloading, resulting in an increased possibility of an asthmatic episode in the case of individuals most likely to display EIA (10,30). Researchers have shown that during a usual 90 minutes of football immense loadings of variable intensity are developed whereas each player according to field position covers great distances causing the heart rate to reach 185–190 pulses per minute (ppm) (2,35). Equal intensity demands were also noticed in basketball although it is usually played indoors and has a shorter overall duration with more breaks between compared with football (34).

Indeed, different types of exercises create different degrees of physical challenge (6) with free running inducing bronchospasm of higher intensity compared with running on a cycle ergometer (1,5). However, numerous studies have shown that a significant number of athletes with EIA in football and other sports still remain undiagnosed, suggesting that different types of exercises carry different EIA risks (7,30).

Previous studies have also suggested that physical activities in water such as swimming carry a lower frequency of EIB occurrence because of the warm and humid climatic conditions of the water environment (1,34). However, on reviewing the literature, it seems that in the case of water polo, a demanding sport of a similar intensity compared with other nonwater team sports (14), no studies examining its relationship with EIB have ever been conducted. Thus, a necessity is created to determine whether EIB is linked not only with exercise intensity but also with the environmental conditions that are present during training.

The purpose of this study was to examine, by using the free running test, whether there were any differences in EIB occurrence between adolescent athletes of 3 different sports (football, basketball, and water polo) exercised under different environmental conditions but at a similar exercise intensity.

Methods

Experimental Approach to the Problem

The study was conducted either in club settings relative to each sport or in the Developmental Medicine and Special Education facilities. The main concern of the research was to ascertain in which of the 3 sports a bigger rate of forced expiratory volume in 1 second (FEV1) fall during a free running test would occur for a group of 90 adolescents recruited from football, basketball, and water polo academies (clubs) in northern Greece.

Subjects

The sample consisted of 90 male adolescents (3 groups of 30 individuals) aged 14–18 years. Each group comprised 30 athletes of football (mean age 15.73 ± 1.33 years), basketball (mean age 15.43 ± 0.72 years), and water polo (mean age 15.86 ± 0.97 years), respectively, all with a training background of at least 2 years according to sport. The athletes of all the groups fulfilled the same criteria, that is, (a) same age (p = 0.263), height (p = 0.097), and weight (p = 0.282) with no statistically significant differences present (Table 1), (b) normal development and sexual maturation by means of chronological age (33), (c) a minimum of 2 years training according to sport, (d) absence of any known organic disease, (e) absence of bronchial asthma or pulmonary infection symptoms for the last 12 months before the study, (f) no history of asthma medication or other medication taken during the last 12 months, and (g) no asthma medication intake before, during, or after testing procedures.

Table 1
Table 1:
Anthropometric features of each group.*

All the participants and their parents or legal guardians were informed of the purpose of the study and its procedures and signed a consent document before investigation, which was approved by an Institutional Review Board for the use of Human subjects. The medical history of the participants was obtained using a questionnaire (Table 2) (7, 29) answered with the help and supervision of athletes' guardians. Questions regarding the presence of fatigue or other clinical symptoms during training were answered by the athletes and their coaches.

Table 2
Table 2:
Questionnaire used in the study.

Testing Protocol

All the participants were initially subjected to a clinical examination and cardiorespiratory assessment by a physician and a free running test of a 6-minute duration. The FEV1 was assessed with the help of a microspirometer (Micro Plus Spirometer, Micromedica, Hamburg, Germany).

One week before the measurements, the use of the microspirometer was demonstrated to the participants. According to the test instructions, no warm-up or antiasthmatic drug administration preceded testing procedures (7,9,20). All the measurements were conducted in May, at the same time every day with matching environmental conditions of humidity (mean 40–45%) and temperature (19–21°C) for all the participants.

Initially, the FEV1 rest value for each individual was recorded before the free running test with none of those examined showing any deviation from the expected physiologic FEV1 values. Next, all the participants underwent a running test of a 6-minute duration, at an intensity equal to 80–90% of their MHR. To record submaximal intensity achievement and its control maintenance (170–180 ppm), the heart rate was recorded by means of a portable wireless device (Polar Vantage NV HRM, Polar Electro Oy Co., Kempele, Finland). During the test, the athletes run within a predetermined running pace. Their coach was present and ran together with the athletes with the purpose of monitoring and encouraging the athletes during the running test.

After the free running test, the FEV1 value was measured and recorded for each individual according to the protocol at t = 2, 5, 10, 15, and 30 minutes. Next, a comparison was made between FEV1 rest (initial) value with each one of FEV1 values measured after exercise with the highest FEV1 drop recorded for each athlete according to the following type:

An FEV1 fall ≥10% at least in 1 measurement was considered as abnormal (16). The presence of fatigue or dyspnea, shortness of breath, and chest tightness symptoms was also monitored.

Only the athletes exhibiting a ≥10% drop of FEV1 were reevaluated using the micro spirometer during a training session to record FEV1 values (5,6,15). Intensity of exercise throughout training was scrutinized by using a portable wireless device equipped with an audible alarm each time the heart rate reached 170–180 pulses. In this case, the FEV1 measurement took place with the use of a microspirometer record FEV1 values during exercise and compare them with FEV1 rest values before training. The values were recorded for each participant in a standing position taking a deep breath and exhaling with all force in the microspirometer in 3 separate efforts. The highest value achieved was recognized as the best effort used for comparison.

Statistical Analyses

The statistical package SPSS for Windows, version 12.0, was used for all data analyses (Chicago, IL, USA). One-way analysis of variance (ANOVA) was used to examine the effect of the type of sport (football, basketball, and water polo) on FEV1 levels during the free running test and during training. In the case of significant differences, the LSD post hoc test was also applied. The alpha level was set to p ≤ 0.05.

Results

Examination of all the participants during the free running test showed that 22 athletes, that is, 9, 8, and 5 football, basketball and water polo athletes, respectively, demonstrated a >10% FEV1 drop (Table 3), whereas the ANOVA of FEV1 respiratory indicator showed no statistically significant differences between groups (F(2, 19) = 3.77, p = 0.323, η2 = 0.112, p = 0.231) (Table 4). The severity of asthma of 21 participants varied between 10 and 20% (95.4% of the athletes exhibiting mild asthma), whereas one football athlete (4.5%) displayed moderate asthma with a 20–40% FEV1 fall range. Overall, the percentage of athletes showing a >10% of FEV1 drop according to sport was 15.02% for football, 13.65% for basketball, and 13.02% for water polo.

Table 3
Table 3:
Medical history and decrease in FEV1 ≥ 10% during the free running test among the athletes of the different sports.*
Table 4
Table 4:
Mean ±SD of the decrease of FEV1 of athletes with EIA during the free running test and the sports training.*

Previous researchers have regarded the free running test as a reliable and valid procedure to diagnose and evaluate EIA (5,7,20,21); hence, only the participants demonstrating a >10% FEV1 drop during the running test were reevaluated during training. Reevaluation of the 22 participants during training showed that water polo athletes did not present a >10% FEV1 drop in training conditions, whereas in 5 out 9 (55%) football athletes and 4 out of 8 of basketball athletes, a ≥10% FEV1 drop was evident (Table 4). Thus, an ANOVA was conducted only for the other 2 teams, and this revealed no statistically significant differences existing between the 2 groups (F(2,19) = 3.77, p = 0.351, η2 = 0.125, p = 0.140). Despite the absence of significant statistical differences, the η2 value suggests that the differences were meaningful.

In relation to medical history, from all the participants showing a ≥10% FEV1 drop in training conditions, 4 adolescents had a clear medical record, 6 had a history of allergies, and 3 had a history of asthma (Table 5).

Table 5
Table 5:
Medical history and decrease in FEV1 > 10% among the athletes during the training in each sport.*

Discussion

In this study, the results showed that 22 out of the 90 (24.4%) participants who were subjected to the free running test responded with a ≥10% FEV1 decrease, whereas during training conditions, respiratory measurements of the 22 participants showed that only 9 of them presented an FEV1 decrease of ≥10%. Furthermore, the 6-minute duration free running test at an intensity equal to 80–90% of the MHR did not produce statistically significant differences between the 3 types of sport, even though the water polo athletes demonstrated a lower EIA percentage.

It seems that the small sample of this study influenced the power of statistical analysis, in agreement with the notion of Sultive and Ulrich (32) who concluded that for conditions that are infrequent in the general population, studies with a small number of participants do not always reveal significant statistical differences among groups. However, Sultive and Ulrich (32) also noted that to a certain extent in cases similar to those of our study a trend of differences between groups should also be considered indicative. Indeed, despite the absence of any significant statistical differences between the 3 groups of this study, the η2 analysis does show a trend of lower incidence of EIA of water polo athletes.

Thus, the results agree with those of other research studies concluding that a higher incidence of EIA is evident among athletes in certain outdoor sports such as alpine skiing (8) and long distance running events (13) compared with those of swimmers (11,12), verifying the hypothesis that certain environmental conditions related to environment temperature and humidity conditions according to sport can affect EIA occurrence. The fact that during the free running test held outdoors water polo athletes exhibited EIA as compared with respiratory measurements obtained during the water polo training held indoors in which athletes did not have EIA further strengthens the notion concerning the influence of environmental conditions in sport settings.

The results agree with those of studies investigating the value of swimming and other water sports because of the humid and warm environment provided for children with asthma (5,12,22,36). Especially water polo is an activity of low breathing demands per minute; thus, it is considered as a sport of low probability to induce EIA. Most important is that children with asthma respond psychologically in favor of water sports because they can perform all activities without any respiratory episodes (25). In our study, however, no questionnaire was administered to the athletes to ascertain whether they had chosen to participate in different sports because of past experiences associated with difficulty in breathing, because criteria selection of the participants included absence of bronchial asthma or pulmonary infection symptoms and no history of asthma medication or other medications taken for the past 12 months before study.

Prevalence of EIA among football athletes was higher during the free running test because continuous running induces a more severe bronchospasm compared with many interruptions occurred during football training, which leads to a nonincrease of intensity for long periods of time (7,29,31). Both football and basketball are sports that are characterized by high-intensity aerobic demands but low-duration activity bursts alternate rhythm that do not cause severe asthma attacks and induce EIA at a lower frequency compared with the free running test in which a continue submaximal intensity produces EIA more easily.

Water polo requires more frequent maximal efforts than do the other 2 outdoor sports because of the high water resistance during exercise; however, it is considered a safer sport for children with a medical history of asthma or allergies because of the environmental conditions and the quality of the air causing a lower incidence of EIA (1,3,17,27). According to Cypcar and Horton (4), water and electrolyte loss increases osmolarity of bronchial mucous, which in turn can cause EIA, which is less likely to happen in water sports. Thus, bronchial hyperactivity seems to be directly correlated to the environmental conditions and the intensity of the exercise undertaken.

Furthermore, the results of this study showed that young athletes with no clinical history of asthma or allergy hypersensitivity can manifest EIA during the free running test in agreement with the findings of other epidemiological studies, suggesting that undiagnosed EIA is a frequent problem for young athletes and their trainers (23,26,27,28). In case this respiratory problem remains undiagnosed when combined with dry, cold, and full of antigens, air conditions can further deteriorate the health and performance of young athletes (26,27).

Practical Applications

Football and basketball are by far the most popular sports that Greek adolescents choose to participate for athletic and social reasons. Unfortunately, most schools in Greece do not have a water-based sport option for young athletes. Furthermore, neither the educational policy takes into account the importance of water sports to protect emotionally youngsters who choose football and basketball and get disappointed or forced to stop relative sport participation because of asthma attacks that occur during training.

First, the study points out that establishing a routine checking of the respiratory status for possible EIA in young athletes playing different sports is of great importance, because EIA can be held responsible for negative behavioral changes in youngsters who are willing to participate in sports but are unable to do so because of asthma attacks during exercise (24). Respiratory checking through simple testing and easily applicable procedures such as the free running test used in this study should be formally included in educational policies for all young athletes. In some cases, what is more important is not the preference toward a specific sport but the redirection of young individuals by PE teachers to participate in water activities held indoors for health reasons. Because EIA occurrence is lower even in the case of water polo, which requires great effort demands similar to that of football or basketball, redirecting youngsters with an asthma tendency toward water sports is most important.

An alternate option applicable for children with EIA in Greece and in similar coastal countries with good weather conditions is always the organization of swimming and water polo activities in the sea. Another option is the adaptation of training in football and basketball by incorporating relaxation exercises, respiratory activities, and interval training to make a further increase of training load more bearable (29,31) in these sports. Further studies need to be conducted to evaluate the response of young athletes to different treatments and alternative training programs that can prevent EIA occurrence.

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Keywords:

free running test; sports; activity; bronchospasm; exercise intensity

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