Unlike exercising in the often dry air of the gym, or contending with seasonal allergies or frigid winter air, swimming provides the chance to work out in moist air, which can help reduce exercise-induced asthma symptoms.
Not only can pool workouts help you avoid asthma attacks if you're prone to them, some studies have shown that swimming can actually improve the condition overall. According to a study published in the scholarly journal, Respirology, when a group of kids completed a six-week swimming program, they saw improvements in symptom severity, snoring, mouth-breathing, and hospitalizations and emergency room visits [source: Science Daily]. What's more, the health benefits were still apparent a year after the swimming program had ended [source: Physorg].
Even those without asthma could benefit from swimming, say the study's authors, as the exercise can increase lung volume and teach proper breathing techniques.