The experience of suddenly breathing easier shortly after starting a workout is a common and immediate effect of physical exertion. This temporary decongestant action is a direct physiological response to the body preparing for sustained activity. Understanding this effect requires looking into the internal signals that govern the body’s shift from rest to action.
The Role of the Autonomic Nervous System
The primary trigger for the decongestant effect lies in the activation of the autonomic nervous system (ANS), the body’s involuntary control center. Exercise immediately signals the sympathetic branch of the ANS, commonly known as the “fight or flight” response, to take over. This rapid activation prepares the entire body for increased physical demands, including boosting heart rate and diverting blood flow to the working muscles.
A key part of this systemic response is the swift release of hormones called catecholamines into the bloodstream. The adrenal glands pump out epinephrine, also known as adrenaline, which circulates throughout the body. This surge of epinephrine acts as a powerful signal that initiates the clearing of the nasal passages and drives the reduction in congestion.
Reducing Swelling Through Blood Flow Changes
Nasal congestion occurs because the mucous membranes lining the nasal passages are swollen due to engorged blood vessels. These membranes contain specialized, highly responsive blood vessels called venous sinusoids that can quickly dilate or constrict. When a person is congested, these vessels are dilated, increasing the volume of tissue and narrowing the airway.
The epinephrine released during exercise acts directly on these vessels, functioning as a potent vasoconstrictor. Vasoconstriction is the process where the walls of blood vessels tighten and narrow their diameter. The narrowing of these venous sinusoids forces blood out of the nasal lining, which rapidly decreases the swelling within the nasal cavity. This reduction in tissue volume effectively opens the airways, providing the sensation of clearer breathing during the workout.
When Exercise Does Not Clear Sinuses
While exercise often acts as a temporary decongestant, this effect is not universal, and some individuals may experience the opposite reaction. In these cases, the decongestant effect of the sympathetic nervous system is overridden by other factors. A condition known as Exercise-Induced Rhinitis (EIR) can cause symptoms like a runny nose, sneezing, or even congestion during or after physical activity.
EIR is often triggered by environmental irritants or changes in airflow, not a failure of the body’s internal mechanism. Breathing heavily, especially in cold, dry air, can cause the nasal lining to become irritated or dehydrated, leading to inflammation and increased mucus production. Similarly, exercising outdoors can increase exposure to allergens like pollen and dust, which triggers an allergic response that can cause congestion despite the adrenaline-induced vasoconstriction.