Exercise-Induced Bronchodilation: Running-Induced ‘Asthma’

This article was written by Hanny Allston, who is a former winner of the Melbourne Marathon and Cadbury Marathons.  In 2006 she also won the world sprint orienteering title.  Since then, Hanny has studied medical research and worked at the AIS.

Standing on the start line.  Its cold and you feel slightly short of breath due to the anxiety of the race ahead.  Once the gun goes and the first few hundred meters have been run, you relax slightly and find your rhythm.  The chest tightness lingers.  You maintain your stride and cross the finish line.  However, as you pull up and begin to walk towards the refreshments you start to cough.  You try to talk to your friends and family but you continue to cough for a long time after the race.  You are probably experiencing Exercise-Induced Bronchodilation.

Asthma is a common chronic inflammatory condition of the lung airways characterized by any of the following symptoms: coughing, chest tightness, wheezing and shortness of breath.  The symptoms can be brought on by either external stimulants or internal physiological changes that cause: limitation to the airflow; airway hyperresponsiveness to a wide range of stimuli; and inflammation of the larger airways called bronchi (Kumar & Clark, 2005).  These effects are usually reversible, either with or without medical treatment (Australian Institute of Health & Welfare, 2011).  The severity of asthma ranges from mild, intermittent symptoms that cause few problems, to severe and persistent wheezing and shortness of breath.  In the most extreme cases, asthma can result in death and any onset of symptoms should be taken seriously.

If the statistics are correct, one in ten of everyday Australians will experience asthmatic symptoms.  In fact, it is one of the most common burdens of disease in our society and in 2004-05 alone, asthma cost Australians $606 million dollars, approximately 1.2% of our health expenditure (Australian Institute of Health & Welfare, 2011).  However, recent research suggests that our running cohort is at even greater risk of asthma.  In a fun run, this could equate to 1/5^th of the race’s starters.

Asthma remains the most common health problem among elite athletes (Arie, 2012).  A study conducted during the Athens Olympics in 2004 found that 21% of the Great Britain Olympic Team were ‘asthmatic’, compared to just 8% of the British population (or 10% of the Australian population) (Arie, 2012).  This study concluded that the athletes’ symptoms appeared to be exercise induced.

For many years, little was understood about why such a healthy cohort would have more respiratory problems than the ordinary population and how exercise could actually induce asthma (Arie, 2012).  Suspicions arose.  Were some athletes declaring themselves asthmatic because inhalers could enhance performances? Thankfully, in 2012 more is understood about this widely experienced condition and our elite athletes no longer require authorized exemption for the use of asthma inhalers at the international level.

Unfortunately all runners, not just the elite, are at risk.  In 2011, Robson-Ansley et. al. studied 208 runners in the 2010 London Marathon.  They concluded that, ‘The prevalence of allergy in recreational marathon runners was similar to that in elite athletes and higher than that in the general population’.  They suggested that the runner’s symptoms were also exercise induced

The problem with exercise: Exercise-Induced Bronchoconstriction

So what triggers the onset of asthma and why do runners have an increased risk? The answer lies in triggers that lurk unseen in the air we breathe in as we run. Exercise-induced bronchoconstriction (EIB) is a transient, reversible bronchoconstriction that develops after strenuous exercise (Randolph, 2006). The term exercise-induced asthma has now become redundant as exercise does not induce asthma but rather the narrowing of the airways, bronchoconstriction, that leads to asthmatic and non-specific symptoms. It is normally associated with at least five to ten minutes of continuous exercise and is particularly prevalent when the inhaled air is dry and/or cold.  Bronchoconstriction can also be triggered by: viral infections; exposure to allergens such as house dust mites, pollen and animal dander; irritants such as tobacco smoke, some food additives, smoke, fumes and dust; cold air and exercise (Australian Institute of Health & Welfare, 2011). 

Endurance athletes often train and race at a ventilation rate greater than 85% of their VO2max.  This results in increased inhalation of aeroallergens, air pollutants and cold/dry air compared to the nonexercising population (Randolph, 2006).  At these high rates, mouth breathing becomes necessary so the inspired air bypasses the normal air-conditioning environment of the nasal passages and cause irritation to the lung airways.  Resulting complaints range from shortness of breath, coughing and potentially longer-term complications, such as an increase in respiratory-like illness (Dickenson et. al., 2005). 

If you find yourself travelling from humid to dry, warm to cold, or Autumn to Spring environments, you may be particularly at risk.  During such situations, you may find yourself coughing and wheezing, and no longer able to keep up with your peers.  Symptoms can even include stomachaches or sore throats in younger athletes. EIB with asthma is often the first sign of asthma in up to 90% of patients with that disease and any new symptoms should be discussed with a doctor.

What can you do to avoid EIB?

Poorly managed asthmatic symptoms have the potential to impair an athlete’s performance but not all asthma-like symptoms are necessarily brought on by EIB.  Robson-Ansley (2011) scientifically observed a twofold increase in reported Upper Respiratory Tract symptoms in runners compared to non-runners.  These runners also showed a decrease in performance.  They determined that although some runners’ symptoms were caused by an increase in infection due to acute suppression of the immune system, (a relatively common occurrence after prolonged high intensity exercise, such as a long-distance or multi-day race), at least two-thirds of runners, symptoms could be contributed to EIB. 

Before attributing any symptoms you may have to EIB (asthma), it is important to consult your doctor and take into account any changes in the environment and competition or training workload.  It would seem wise to heed the advice of Sergio Bonini, professor of internal medicine at the Second University of Naples, Italy - “Strenuous and continued exercise and training increase the types of cells that cause illness, allergy and asthma.” (Arie, 2012)

Although there are treatments available for asthma, the worst-case scenario would be an intense attack of shortness of breath during the race that curbed performance.  Evidence has shown that in order to prevent such an exacerbation, runners who know that they can experience symptoms should aim to conduct high-intensity warm-ups that include intervals (Helenius et. al., 1998).  Michleborough et. al. (2007) also found that combining the interval warm-up with salbutamol, a dilator of the smooth muscle surrounding the bronchi, prior to competition resulted in substantial bronchodilation, more effectively protecting against EIB than just a treatment intervention alone.

In summary, any runner concerned about respiratory tract problems that arise during or after exercise should consult a physician and discuss their symptoms.  Further to this, substantial changes in your everyday environment such as travelling to compete in a cooler climate may trigger EIB, even when you have no prior history of asthma.  Once again, consulting a physician and discussing your concerns may provide that extra boost of confidence on race day.

References:

Arie, S. (2012) What can we learn from asthma in elite athletes? British Medical Journal. doi: doi=10.1136/bmj.e2556

Australian Institute of Health and Welfare, Australian Centre for Asthma Monitoring. (2011) Asthma. Retrieved from http://www.aihw.gov.au/asthma/

Dickinson J.W., Whyte G.P., McConnell A.K., & Harries M.G. (2005) Impact of changes in the IOC-MC asthma criteria: a British perspective. Thorax. 60: 629-32.

Helenius, I. J., Tikkanen, H. O., & Haahtela, T. T. (1998). Occurrence of exercise induced bronchospasm in elite runners: dependence on atopy and exposure to cold air and pollen. British Journal Of Sports Medicine, 32(2):125-129

Kumar, P. & Clark, M. (eds.) (2005) Clinical Medicine, 6^th Ed. Elsevier Saunders. 912-914

Michleborough, T. D., Lindley, M. R., & Turner, L. A. (2007). Comparative Effects of a High-Intensity Interval Warm-Up and Salbutamol on the Bronchoconstrictor Response to Exercise in Asthmatic Athletes. International Journal Of Sports Medicine, 28(6), 456-462. Retrieved from http://www.thieme.com.

Randolph, C.C., Dreyfus, D., Rundell, K.W., Bangladore, D., & Fraser, B. (2006). Prevalence of Allergy and Asthmas Symptoms in Recreational Roadrunners. Medicine & Science in Sports & Exercise. 38(12), 2053-2057. doi: 10.1249/01.mss.0000235357.31932.43

Robson-Ansley, P., Howatson, G., Tallent, J., Mitcheson, K., Walshe, I., Toms, C., Du Toit, G., Smith, M., & Ansley, L. (2012). Prevelence of Allergy and Upper Respiratory Tract Symptoms in Runners of the London Marathon. Medicine & Science in Sports & Exercise. 44(6), 999-1004. doi: 00005768-201206000-00003.