Fitness nuts beware: Exercise can actually cause asthma. Well, sort of. Alongside asthma, a respiratory condition where the lungs’ airways tighten and breathing becomes labored, sits exercise-induced bronchoconstriction (EIB). More commonly, it’s called exercise-induced asthma. Unlike asthma, which stems from all sorts of factors—think family history, air pollution and obesity—EIB rises in response to strenuous exercise. The most common theory is that the increase of breathing during a workout causes your airways to dehydrate and the muscles to contract. Crucially, that phenomenon isn’t restricted to those with the more conventional form of asthma. Even those without it might experience EIB.
Also important to note: Because of the conditions that cause EIB to arise, it can be tough to spot. Maybe you get back from a job and feel a tighter chest and shorter breath than normal. That could be EIB, but easy to chalk up to a particularly tough workout. Delineating the difference between and between a visceral reaction to intrepid miles paces and a diagnosable condition can become blurry when both lead to heavy panting.
But there are subtle differences. Individuals experiencing EIB might notice that a shortness of breath lasts longer than it takes your breath to return to normal post-workout. In the case of an exercise-related asthmatic reaction, breathing problems might persist for up to an hour after the workout is over. In some cases, nausea surfaces too. But that isn’t much to go on.
In 2018, a study in the medical journal npj Primary Care Respiratory Medicine described the prevalence of EIB as “likely to be underestimated.” Acknowledging that the condition’s prevalence is guesswork, the same study suggests that up to 20 percent of the general population experiences EIB—and that among Olympic athletes the number may be 70 percent. For patients with a conventional asthma diagnosis, the number is more like 90 percent.
Beyond resembling some conventional reactions to exercise, the various means testing for EIB further muddles how widespread the condition is. Depending on where you are, you may be asked to run on a treadmill, ride a stationary bike, or simply run a given distance to spur EIB for testing. A handful of different tests are used to determine whether someone has EIB, and none have become the gold standard. All of this continues to warp the picture of how widespread EIB is, and why many people who have it might not know.
To be clear, none of those are reasons to avoid consulting a physician. Even without strict standardization in place, EIB is still diagnosable, opening the door to a suite of possible treatments. Some athletes induce something called a “refractory period,” which temporarily reduces susceptibility to EIB, through pre-exercise. Others breathe through a mask or scarf for a period before working out to humidify their airways, too. In more serious cases, an inhaler might enter the picture.
Despite the obscurity of a condition potentially so widespread, the treatments to EIB seem to work. But nipping it in the bud requires a little investigatory legwork with your physician. It could lead to your fastest mile yet.