Experiencing shortness of breath when walking or biking is likely caused by one of two things. You may reach your natural threshold for physical exertion, which leads to a shortness of breath. Or you may experience a sense of feeling winded or breathless during physical activities owing to a condition known as exercise-induced asthma. Your doctor can often help you determine the cause of your discomfort.
If you lead a relatively sedentary lifestyle, walking or biking could lead to some respiratory impediments beyond rapid breathing. Physical activity causes an increase in respiration rate—and heart rate—to meet the increased need of your muscles for oxygen. If your body is unaccustomed to physical exertion, your heart and lungs don't work as efficiently, so they may be unable to meet this demand. This inability causes you to feel winded or breathless.
Improving your fitness level is one of the easiest methods of preventing shortness of breath. Instead of avoiding exercise entirely, start off slowly with 10-minute intervals of walking or biking. Continue to increase the duration of workouts as your sense of feeling winded or breathless improves. Eventually, you won't experience shortness of breath during your athletic pursuits.
Asthma is another common culprit for the shortness of breath when walking or biking. When you develop this condition, physical exertion triggers a narrowing or swelling along your airways, causing difficulties getting enough oxygen into your lungs. People with exercise-induced asthma may have no other triggers aside from exercise.
Although no cure exists for asthma, it need not deter you from working out. You can take several medications before or during exercise to prevent shortness of breath and any other associated symptoms. Albuterol, a bronchodilator, can open your airways once shortness of breath begins, but you can also take corticosteroids, leukotriene modifiers, long-acting beta agonists or theophylline to avoid symptoms altogether. Talk to your doctor to determine which medication is best for you.
Although fitness level and exercise-induced asthma are the most common causes of shortness of breath during exercise, you may experience this symptom during exercise if you have a cardiovascular condition. Conditions ranging from cardiomyopathy to atherosclerosis to heart disease can affect the transport of oxygen to your muscles, leading to an abnormal level of breathlessness while exercising. Your doctor can help you determine whether you have a cardiovascular condition.