Why Do I Struggle To Breathe When Running? 4 Potential Causes

Lots of new runners ask questions such as, “Why do I run out of breath so easily?” or “Why do I struggle to breathe when running?”

Feeling like you’re huffing and puffing or totally out of breath while running is certainly not uncommon.

There are quite a number of potential causes of shortness of breath while running or difficulty breathing during exercise.

In this article, we will answer your question, “why do I struggle to breathe when running,” discuss common causes of shortness of breath during running, and how to not run out of breath while running.

We will cover the following: 

  • Why Do I Struggle to Breathe When Running?
  • Why Do I Run Out of Breath So Easily While Running?

Let’s jump in!

A runner out of breath, with eyes closed, resting her hands on her back.

Why Do I Struggle to Breathe When Running?

There are a number of reasons why you might feel out of breath while running, some of which are a matter of poor conditioning (which should resolve as you become fitter).

However, shortness of breath during exercise can also be due to underlying medical issues.

For this reason, it’s important not to ignore difficulty breathing when running, particularly if it’s frequent and seems to happen under a variety of conditions, and especially in cases where you have been training for a long time and have good cardiovascular and cardiorespiratory fitness.

For example, if you have an underlying condition, such as asthma, that is undiagnosed or is not being well managed, additional treatment or adjustments to your medication may resolve the issue and will reduce the risk of more dangerous sequela, such as an asthma attack. 

Why Do I Run Out of Breath So Easily While Running?

Difficulty breathing while running or during exercise is termed dyspnea. 

A runner out of breath, hands on knees.

Dyspnea can not only reduce athletic performance and increase fatigue, but it can also dissuade you from wanting to work out or run. After all, it can be quite unmotivating to exercise if every time you try to go running, you’re out of breath or feel shortness of breath.

There are four primary reasons why you might feel short of breath during running: you’re a beginner, and your fitness isn’t good yet, you’re running too fast for your ability level, or you have asthma or another underlying respiratory condition.

Let’s get into each of these potential causes in detail:

#1: Your Fitness Is Poor

The most likely reason that you feel out of breath while running is simply due to the fact that you’re not yet in “good shape” and your body has not yet adapted to the rigors of running.

Consistent aerobic exercise improves the efficiency and health of the cardiovascular system, and your lungs and breathing muscles will become stronger and more accustomed to breathing deeply and rapidly.

A runner out of breath supporting herself against a wall.

#2: You Are Running Too Fast

Another common reason why you might feel out of breath while running is that you are running too fast for your current fitness level. 

Remember running is a total-body workout. Your heart and muscles need much more oxygen and nutrients above resting levels, requiring your lungs to work harder and faster to take in oxygen and exhale carbon dioxide, the metabolic waste product.

The faster you run, the higher the energy cost of the activity per minute. This means that as exercise intensity increases, so does the rate at which your muscles and heart need oxygen.

As a result, your body tries to breathe faster and deeper, aiming to gulp in as much oxygen per minute as possible.

Once you cross over the anaerobic threshold, your body is no longer able to produce energy (ATP) fast enough through aerobic metabolic pathways (Krebs cycle and electron transport chain).

Thus, the reliance on anaerobic glycolysis increases significantly.

Anaerobic glycolysis does not require oxygen to produce energy, and it’s not as efficient of an energy-generating pathway. Additionally, anaerobic glycolysis produces end products that, in turn, cause rapid fatigue and a further increase in respiration.

A sweaty runner out of breath.

When energy is produced in your muscles without oxygen, lactate and hydrogen ions (acid) are created. The lactate molecules can be further broken down to usable energy, but the hydrogen ions accumulate, causing an acidic environment in your muscles and decreasing the pH in your muscles and blood.

This creates the dreaded burning sensation you have probably experienced in your legs when running at a fast speed and the resultant fatigue that makes your legs feel heavy and lead-like.

There are various means to help buffer this acid to help attenuate metabolic acidosis, but this can increase the carbon dioxide level in your blood.

The body can only safely operate under a finite concentration of carbon dioxide because too much of this compound is toxic. Fortunately, we have a built-in mechanism to rid the body of excess carbon dioxide—exhalation.

Therefore, you will start breathing harder and faster as you rely more and more on glycolysis in order to expel the excess carbon dioxide that begins accumulating in the body. This, in turn, will further contribute to you feeling out of breath while running. 

Slowing down and staying at a running pace that is below your anaerobic threshold will help prevent this sharp increase in ventilation needs.

A person sitting on the stairs, out of breath.

#3: You Have Asthma

If you’ve been running for quite some time but still have trouble breathing while running, you might have undiagnosed or poorly-managed asthma. 

Asthma is a chronic lung disease that causes inflammation in the airways. 

Some runners have chronic asthma that can be problematic during most activities of daily living, but it’s also common to have exercise-induced asthma wherein your asthma symptoms are triggered by physical activity and exacerbated by activities such as running.

Untreated or poorly managed asthma can increase the risk of experiencing an asthma attack, an acute and potentially serious fit of asthma symptoms that can make getting an adequate amount of oxygen extremely difficult, even at rest.

Rescue inhalers are designed to help rapidly open up the airways and quell inflammation so that you can breathe more easily.

The following are pointers on how to not run out of breath while running with asthma.

The American Lung Association recommends that people with exercise-induced bronchoconstriction (EIB, or exercise-induced asthma) try a couple of things to reduce the degree to which their asthmatic symptoms negatively impact their ability to exercise.

A person pumping an inhaler.

For starters, warming up with some gentle cardio exercise and stretching will help gradually increase your heart rate and breathing rate so that it isn’t such a shock to your system once you start moving at a more vigorous pace. A 5 to 10-minute warm-up is recommended. 

This might include brisk walking, gradually increasing the pace, gentle cycling on a stationary bike, marching in place, or performing some other form of light aerobic activity.

Dynamic stretches such as walking lunges and skipping can then get your muscles and joints moving and continue to prime your cardiovascular and respiratory systems for the workout ahead.

Speaking with your healthcare provider about the best medication management plan and pre-medicating before your workout can potentially make it easier to breathe during exercise and reduce the severity of asthmatic symptoms during your workout.

It’s also helpful to pay attention to your specific triggers aside from exercise in general. For example, is it harder to breathe when you are running in cold weather or when the air is really dry? Is your asthma worsened by seasonal allergies when pollen counts are high?

Keeping a log of things that trigger your EIB can help you determine the best time of day to run and/or ways to modify your workout to reduce the incidence of breathing difficulties.

For example, if cold, dry air makes it especially hard to breathe while running, consider wearing a buff or facemask to help warm and humidify the air.

Try to breathe through your nose, as nasal breathing during running affords the benefit of warming and moisturizing the air before it hits your lungs, cutting down on the irritating nature of cold and dry air when it otherwise reaches your airways.

A person having difficulty breathing while running in the cold.

#4: Other Medical Reasons

According to research, exercise-induced bronchoconstriction (EIB), which was just discussed, and exercise-induced laryngeal obstruction are two common causes of dyspnea in athletes. Both of these essentially involve some amount of airway dysfunction. 

However, there are also other potential health reasons that you might be out of breath during exercise. For example, iron deficiency and anemia both affect your body‘s ability to transport enough oxygen to your working muscles.

This can cause you to have to breathe more rapidly while still feeling under-satiated in terms of meeting your oxygen needs.

If you’re new to running and struggling to breathe, be patient with your body adapts, take walking breaks as necessary, and slow down! 

Your fitness will improve, but you must slow down to allow your body to take in enough oxygen per minute.

If you have concerns about asthma or other medical issues, be sure to speak with your healthcare provider.

If you would like to learn about the differences between mouth and nose breathing while running to see what you should be doing, check out our article: Mouth Vs Nose Breathing While Running: A Detailed Comparison.

A person having difficulty breathing while running.
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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