Winter Wheeze: Exercise-Induced Bronchoconstriction in Cold Air and Chlorinated Pools

Many triathletes notice something in winter. A hard interval session on a frosty morning leaves you with a hacking cough for an hour afterwards. A threshold set in a warm, chlorine-heavy pool ends with a tight chest. A cold parkrun leaves you wheezing in a way summer racing never did. Plenty of athletes put it down to "a winter cough" or being unfit.

Sometimes it's something more specific: exercise-induced bronchoconstriction, or EIB. This article explains what EIB is, why cold air and indoor pools are classic triggers, how common it is in endurance athletes, and why the answer is testing rather than guesswork. It isn't a guide to diagnosing or treating yourself, and nothing here replaces a medical assessment.

TriForward's "Running in the Cold" covers cold-weather running more broadly, and "Train Through a Cold?" covers infections. This piece is about the airways.

What EIB is

A 2013 clinical practice guideline from the American Thoracic Society, led by Parsons and published in the American Journal of Respiratory and Critical Care Medicine, defined EIB as acute narrowing of the airways caused by exercise. Key points from it:

• It's common in people with asthma, but it also occurs in people without a known asthma diagnosis.
• Symptoms typically include cough, wheeze, chest tightness and breathlessness, usually during or shortly after hard exercise.
• Diagnosis depends on lung function testing, comparing breathing tests before and after exercise or another challenge, rather than symptoms alone.

The usual explanation, set out in the Kippelen review below, is that breathing large volumes of air during hard exercise dries and stresses the airway lining. In susceptible people, that can trigger the airways to narrow, and repeated injury may contribute to longer-term airway hyper-responsiveness. Cold winter air holds very little water, which is one reason cold, dry conditions are such a common trigger. Irritants in the air, such as the chlorine by-products in indoor pools, can add to this.

Why endurance athletes are over-represented

Olympic athletes

A 2012 overview by Fitch in the British Journal of Sports Medicine used data from five Olympic Games, based on athletes who applied to use inhaled asthma medication and had documented asthma or airway hyper-responsiveness.

• About 8% of athletes had asthma or airway hyper-responsiveness, the most common chronic medical condition among Olympic athletes.
• It was markedly more common in endurance athletes, in both Summer and Winter sports.
• Many were diagnosed later in life, which suggests that years of endurance training may contribute.
• Cold or polluted air was considered a significant factor in some sports.

Swimmers and cold-air athletes

The most relevant study for triathletes is a 2009 study by Bougault and colleagues in the European Respiratory Journal, because it compared the two exposures triathletes get in winter. It included 32 elite swimmers and 32 elite cold-air athletes, alongside 32 people with mild asthma and 32 healthy controls.

• Airway hyper-responsiveness was found in 69% of swimmers and 28% of cold-air athletes.
• Airway inflammation, measured as neutrophils in sputum, rose with weekly training hours in both athlete groups.
• Signs of damage to the airway lining were present in most elite athletes and may contribute to hyper-responsiveness.

These were elite athletes training many hours a week, and the abstract doesn't give the sex split. Airway hyper-responsiveness, measured with a chemical challenge, isn't identical to EIB, though the two overlap. But the study shows that both pools and cold air are linked to airway problems in heavily trained athletes.

Triathletes

There's very little research on triathletes. A 2007 study by Knöpfli and colleagues in the British Journal of Sports Medicine followed 7 athletes from the Swiss national triathlon team, none of whom had asthma at the start, for two years. They were tested with an 8-minute outdoor track run at threshold intensity in temperatures from about -9°C to 4°C.

• Bronchial reactivity and EIB increased significantly over the two years.
• Three athletes developed bronchial hyper-reactivity during the study.

Seven elite athletes is a tiny sample, and it tells you nothing directly about age-groupers training eight to 12 hours a week. But it's consistent with the wider evidence: hard endurance training in cold air and pools seems to be associated with developing airway problems over time.

Why winter is a double exposure

Inference from the studies above: winter concentrates the two main triggers for triathletes.

• More indoor pool time. Open-water swimming stops for most people, and pool sessions often go up, sometimes with a deliberate swim focus.
• Hard sessions in cold, dry air. Outdoor runs and rides, especially intervals and races such as winter parkruns, cross-country and duathlons.
• Less recovery for the airways. Some athletes swim in the morning and run in the cold in the evening, with little break from either exposure.
• Winter infections. Colds can make airway symptoms worse and blur the picture.

None of this has been studied as a combination in age-group triathletes. But it's a reasonable explanation for why some triathletes only notice symptoms between November and March.

Why symptoms are a poor guide

This is the most important practical finding. A 2001 study by Rundell and colleagues in Medicine and Science in Sports and Exercise tested 158 elite cold-weather athletes (83 men, 75 women) with breathing tests before and after a sport-specific exercise challenge, and asked them about symptoms.

• 26% had a fall in FEV1 of more than 10% after exercise, a common threshold for a positive test.
• Reporting two or more symptoms was almost as common in athletes with normal tests (41%) as in those with positive tests (39%).
• Cough after a race was the most common symptom and was reported more often by athletes with positive tests.
• Symptoms didn't reliably identify or rule out athletes with positive tests.

The authors concluded that relying on symptoms would produce many false positives and false negatives, and that diagnosis should combine an exercise challenge with breathing tests and the athlete's history. In practice, this cuts both ways:

• Some athletes with symptoms don't have EIB. Their cough or breathlessness has another cause, and an inhaler won't help.
• Some athletes with EIB don't notice much. They may simply feel they underperform in the cold.

Getting assessed

If you have symptoms, the evidence points to a medical assessment rather than self-treatment. The ATS guideline describes diagnosis based on a change in lung function after exercise or a similar challenge. In practice, depending on your doctor and health system, this may involve:

• Breathing tests at rest to look for underlying asthma.
• A challenge test, such as breathing tests before and after an exercise test or another challenge designed to provoke airway narrowing.
• A review of your history, including when symptoms happen, in which environments, and whether you've had allergies or asthma before.

A doctor can also look for other causes of breathlessness, some of which, such as heart problems, are important not to miss.

Treatment and prevention

What the guideline recommends

The ATS guideline graded evidence quality from low to high. Its strong recommendations, for people diagnosed with EIB, were:

• A short-acting reliever inhaler before exercise for everyone with EIB.
• Additional daily or pre-exercise medicines for people who still have symptoms despite the reliever.

These are clinical decisions for your doctor, not something to set up yourself. Medicines have different rules in sport, so anyone racing under anti-doping rules should check their prescription's status.

Reducing exposure

A 2012 critical review by Kippelen and colleagues in the British Journal of Sports Medicine concluded that reducing athletes' exposure to irritants is the most important way to prevent or limit airway problems. It found that non-drug strategies can help, while drug treatments haven't been shown to prevent the development of airway hyper-responsiveness. Practical options that follow from this, as inference:

• Choose better-ventilated pools where you can, and avoid swimming straight after heavy pool use if the air feels thick with chlorine.
• Move the hardest efforts indoors on very cold, dry days, onto the turbo or treadmill.
• Breathe through a buff or scarf on easy cold runs to warm and humidify the air a little. This hasn't been tested in the studies here.
• Avoid hard efforts during a chest infection. TriForward's "Train Through a Cold?" covers when to rest.

Warm-ups

There's one non-drug strategy with trial evidence. A 2012 meta-analysis by Stickland and colleagues in Medicine and Science in Sports and Exercise pooled 7 randomised studies of warm-ups before an exercise challenge in people with EIB.

• High-intensity warm-ups reduced the post-exercise fall in FEV1 by about 10.6 percentage points.
• Variable-intensity warm-ups reduced it by about 10.9 percentage points.
• Continuous low-intensity and continuous high-intensity warm-ups didn't produce a statistically significant reduction.

The authors concluded that a warm-up including some high-intensity efforts may be a useful short-term, non-drug strategy. The included studies were small and the abstract doesn't report total participant numbers. Inference: a race or session warm-up that includes a few short, hard efforts is sensible for athletes with EIB, but it isn't a replacement for prescribed treatment.

Racing with EIB

Triathlon adds its own problems for athletes with diagnosed EIB, because the race moves through different environments and warm-ups are often cut short. The following points are inference from the studies above, not tested race strategies, and they sit alongside whatever plan your doctor sets.

• The swim start. Cold open water can make breathing feel out of control in the first minutes, as TriForward's "Winter Open-Water Swimming" explains. For an athlete with EIB, a calm entry and steady first few hundred metres matter even more.
• Warm-up timing. The Stickland meta-analysis looked at warm-ups shortly before an exercise challenge. Race-day logistics, such as closing transition and waiting in a start pen, can leave a long gap between warm-up and start. A short swim warm-up or a few hard efforts on land close to the start may help.
• Early-season and cold races. Duathlons and cold spring triathlons combine hard efforts with cold, dry air. Planning these with your doctor is more useful than reacting to symptoms mid-race.
• Carrying medicine. If you've been prescribed a reliever, think about where it will be during the race, including on the bike and in transition.

A triathlon scenario

The following example is illustrative, not drawn from a study. A 34-year-old triathlete increases her pool sessions to four a week in December and keeps a Saturday parkrun. By January she coughs for an hour after every parkrun and feels tight after hard swim sets. A friend offers her a spare inhaler.

A better approach, based on the evidence above:

• She sees her GP and describes when symptoms happen. She's referred for breathing tests, including a challenge test.
• If she's diagnosed with EIB, she follows the treatment her doctor prescribes and asks about sports rules for her medicine.
• She adds a warm-up with a few short, hard efforts before parkrun and hard swim sets.
• She moves some hard sessions indoors on the coldest, driest days and swims at a better-ventilated pool when possible.
• If tests are normal, her doctor looks for other causes rather than her assuming it's asthma.

Common mistakes

• Assuming a winter cough is just being unfit. Persistent symptoms with exercise deserve assessment.
• Diagnosing yourself from symptoms. The Rundell study shows symptoms alone often point the wrong way.
• Borrowing an inhaler. It may mask symptoms of something else and isn't safe without assessment.
• Skipping the warm-up on cold days. A warm-up with some hard efforts reduced the airway response in trials.
• Pushing through chest pain or fainting. These need urgent medical help, not a harder warm-up.
• Stopping prescribed treatment when you feel well. Discuss changes with your doctor.

Who's most likely to be affected

From the studies above, the athletes most likely to develop airway problems are those training many hours a week, especially in pools and cold air, and those with allergies or a history of asthma. Fitch's finding that many Olympic athletes were diagnosed later in life suggests it can appear in adulthood, so a lack of childhood asthma doesn't rule it out. Most of the evidence comes from elite athletes, and the Rundell study is one of the few to report a near-even split of men and women. Whether age-group triathletes training fewer hours share the same risk isn't known.

What we don't know

• How common EIB is in age-group triathletes. Almost all the data come from elite athletes.
• Whether the swim-plus-cold combination adds up. It hasn't been studied in triathletes.
• Whether airway changes reverse when training volume drops.
• The value of buffs, masks and pool choice. These are plausible but largely untested in this population.
• Sex and age differences in risk and response to treatment.

References

• Parsons JP, Hallstrand TS, Mastronarde JG, Kaminsky DA, Rundell KW, Hull JH, et al. An official American Thoracic Society clinical practice guideline: exercise-induced bronchoconstriction. American Journal of Respiratory and Critical Care Medicine, 2013;187(9):1016–1027. doi:10.1164/rccm.201303-0437ST
• Fitch KD. An overview of asthma and airway hyper-responsiveness in Olympic athletes. British Journal of Sports Medicine, 2012;46(6):413–416. doi:10.1136/bjsports-2011-090814
• Bougault V, Turmel J, St-Laurent J, Bertrand M, Boulet LP. Asthma, airway inflammation and epithelial damage in swimmers and cold-air athletes. European Respiratory Journal, 2009;33(4):740–746. doi:10.1183/09031936.00117708
• Knöpfli BH, Luke-Zeitoun M, von Duvillard SP, Burki A, Bachlechner C, Keller H. High incidence of exercise-induced bronchoconstriction in triathletes of the Swiss national team. British Journal of Sports Medicine, 2007;41(8):486–491. doi:10.1136/bjsm.2006.030569
• Rundell KW, Im J, Mayers LB, Wilber RL, Szmedra L, Schmitz HR. Self-reported symptoms and exercise-induced asthma in the elite athlete. Medicine and Science in Sports and Exercise, 2001;33(2):208–213. doi:10.1097/00005768-200102000-00006
• Kippelen P, Fitch KD, Anderson SD, Bougault V, Boulet LP, Rundell KW, et al. Respiratory health of elite athletes: preventing airway injury: a critical review. British Journal of Sports Medicine, 2012;46(7):471–476. doi:10.1136/bjsports-2012-091056
• Stickland MK, Rowe BH, Spooner CH, Vandermeer B, Dryden DM. Effect of warm-up exercise on exercise-induced bronchoconstriction. Medicine and Science in Sports and Exercise, 2012;44(3):383–391. doi:10.1249/MSS.0b013e31822fb73a