You're feeling pretty good about your fitness. You lift regularly. Hit the treadmill as much as you can manage. Stretch. Then, one day, you're working out, and you feel your chest constrict, your breaths shorten, and coughs cascade out of you—just 10 minutes into an exercise. What gives? You may have experienced a form of asthma, even if you don't have the underlying condition.
Exercise-induced bronchoconstriction (EIB) is a variety of asthma that typically appears after several minutes of strenuous exercise. The vast majority of people with underlying asthma see their symptoms triggered by intense physical activity, but around 20 percent of people without asthma experience EIB. Curiously, the condition appears even higher among serious athletes, with between 30 and 70 percent encountering EIB.
Widespread as EIB may be, some of its particulars continue to elude experts. For example, cold air has long drawn suspicion as the root cause for the condition, as it appears more frequently in brisk conditions and disproportionately plagues athletes in winter sports. Only recently did researchers determine that the more likely cause was dry air. Cold air is usually drier than warm air, which explains the misconception.
But what does that dry air trigger in the lungs of a cross-country skier drawing deep breaths while gliding across a course?
Lining your lungs—and almost every part of you—are mast cells. For the most part, mast cells are a significant immune system component. When your body is under attack, mast cells react by spurring inflammation, a defensive immune response. However, dry air rapidly circulating through your lungs can dry them out and leave airway tissue with unusually high salt content. That alerts the mast cells, which spring into inflammatory action—and shut your airways. Oops.
Tests for EIB are a patchwork, but each one seeks to provoke an episode. On the simple end of the spectrum, a physician may have their patient do strenuous exercise—say, running on a treadmill—and then see how much air they can expel in one second. The results reveal how much the exercise has undercut lung capacity.
But other evaluations won't break a sweat. Another common way to scan for EIB is to administer an Eucapnic Voluntary Hyperpnea (EVH) test. By inhaling a drug called mannitol in powder form through an inhaler, patients can artificially constrict the muscles in their lungs—mimicking the effects of asthma. A physician can surmise whether someone is vulnerable to EIB by testing lung capacity similarly to the exercise test.
Triggering EIB may be a straightforward process—running that way for five minutes—diagnosing it is deceptively inexact. One 2016 Sports Medicine paper found that identifying EIB using EVH and exercise offered inconsistent enough results that it was impossible to name a gold standard for testing.
That can be frustrating. Who doesn't feel winded after a jog? Paradoxically, one signal that you may be more susceptible to the condition is simply getting into shape. If you've kicked off the year by jogging every day and eventually find that strained breathing and coughs increase with your mileage—it might be time to find a physician.
Originally Appeared on GQ