What to do if someone collapses (or crumples) during exercise


Soccer player collapsed on the field with players and ref attending to her.
Exercise-associated collapse, or syncope, usually results in a slow crumpling to the ground, whereas cardiac arrest causes a sudden, crashing fall to the ground with no attempt at self-protection.

No pain, no gain. One more mile. One more rep. Pushing the body to the limits is a way of life for high school, elite, and weekend warrior athletes. But what happens when you push beyond the body’s limits, and it says, “Enough?"

Just watch coverage of the Boston Marathon, and you’ll see runners struggling to crawl across the finish line before passing out. While it looks scary, chances are most of these athletes are experiencing exercise-associated collapse (EAC) and not a medical emergency such as cardiac arrest.

During exercise cardiac arrest is rare, occurring in less than 1 in 100,000 competitive athletes each year and about 100 times annually in U.S. high schools. It’s a scary and extremely urgent medical emergency, as millions learned firsthand when NFL player Damar Hamlin collapsed during Monday Night Football in January 2023. In another high profile incident, Bronny James, the 18-year-old son of NBA legend LeBron James, collapsed while working out with teammates at USC in July 2023, suffering a cardiac arrest. Both athletes survived, thanks to quick actions taken by onsite medical training staffs, and are recuperating.

EAC is far more common and far less life-threatening – albeit dramatic and frightening – particularly when it happens to a young, healthy athlete. EAC is an umbrella term for loss of consciousness during or immediately after physical activity. Syncope, or fainting, is one of the more common forms of EAC and can be caused by controllable factors, such as being dehydrated, overheated, or due to blood pooling in the legs when standing still after exercise.

Research suggests that about 99.8% of athletes who experience EAC recover with gentle movement and oral hydration. In some cases, though, fainting can signal an underlying or undiagnosed cardiac condition such as arrhythmia – an irregular heartbeat.

It’s important to determine quickly what caused a person to pass out. Treatment for cardiac arrest and EAC are very different, and seconds can make a difference between life and death. Often, the first indicator of whether you’re witnessing a medical emergency is how the athlete fell to the ground:

  • EAC may cause a slow crumpling to the ground. The person may stumble or stagger for a few steps, sometimes putting their hands out to try to catch themselves. They may twitch or be quasi-communicative and usually will resume consciousness quickly. EAC is more likely to occur after exercise than in the middle of an exercise effort.
  • Cardiac arrest causes a sudden, crashing collapse with no attempt at self-protection. The body behaves almost like a rag doll with no movement or muscle resistance, and the person will not wake up on their own. Patients who have a cardiac arrest can have jerking muscle movements that look like a seizure, but don’t be fooled, especially if the jerking came after the person fell to the ground. Cardiac arrest should be suspected if the person collapses while in middle of exercise.

Anytime you see someone drop during or after exercise, assume it’s an emergency until proven otherwise. If the person is breathing and has a pulse, it’s likely syncope or EAC and can be managed on the spot, often without emergency care. But if the person isn’t breathing and you can’t find a pulse, act quickly – you could save a life.

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What to do if someone goes into cardiac arrest

The first thing to do when someone collapses from a suspected cardiac arrest is to call 911 and begin hands-only CPR. Ask another bystander to find the closest automated external defibrillator (AED) and bring it to you quickly.

AEDs are designed so anyone can operate them; open the device and follow the audio directions. If the AED detects a rhythm, it will advise you to pause CPR briefly and allow the AED to provide a shock to the patient’s heart. Resume CPR until emergency responders arrive. The chances of survival decrease 10% with every minute that resuscitation is delayed for a patient in cardiac arrest, so don’t hesitate. Anyone can do hands-only CPR.

Mouth-to-mouth resuscitation is no longer necessary. To perform hands-only CPR, kneel next to the person. Place the heel of one hand in the center of the chest. Place your other hand on top. Lock your elbows and push hard and fast at a rate of 100 times a minute. For reference, this is the same tempo as the Bee Gees’ song “Stayin’ Alive.”

Related reading: Think you can’t do CPR? Think again

What can cause cardiac arrest during exercise

For people 35 or younger, cardiac arrest is most often caused by a congenital heart condition, meaning they were born with it, such as long QT syndrome, hypertrophic cardiomyopathy, or arrhythmogenic cardiomyopathy, a condition that causes fat and scar tissue to replace healthy heart cells. The person may not even know they have an underlying heart condition.

Coronary artery disease is the most common cause of cardiac arrest in people older than 35. A blood vessel is blocked, leading to reduced blood flow to the heart and causing an arrhythmia called ventricular fibrillation.

In rare cases, people can go into cardiac arrest after a hard, perfectly timed blow to the chest by a baseball, hockey puck, or contact with another player. This phenomenon is known as commotio cordis.

Related reading: Pre-sports heart screenings: What parents and athletes need to know

What to do if someone faints after exercise

Most people who faint after exercise regain consciousness quickly. Lay them on a safe, flat surface to make it easy for the heart to send oxygenated blood to the brain and respond to clues about what they need. For example, giving fluids for dehydration, snacks for low blood sugar, or shade if they are overheating. Encourage them to take deep breaths and exhale slowly to oxygenate the brain.

What causes fainting after exercise

When you exercise, the heart sends extra blood to the muscles, which contract and pump it back to the heart. If you suddenly stop, the muscles can’t return blood to the heart as quickly. This leaves less blood for the heart to pump to the brain, and you may become dizzy and lightheaded. A couple of examples are a basketball player who is sprinting all out and then stops for a free throw, or a runner who suddenly comes to a stop at the end of a race.

Vasovagal syncope is the most common cause of fainting after exercise. This is a “backfiring” of the nerves that switch the body into protective mode when faced with a stressful trigger. When your brain feels physically threatened, it might instinctively crumple you to the ground so it’s on the same plane as your heart, which then doesn’t have to work overtime to pump blood uphill.

Most exercise-related fainting episodes are not serious but in some cases can be a sign of an undetected heart condition such as arrhythmia or aortic stenosis. Talk with a doctor if you have frequent fainting spells during or after exercise.

Preventing future fainting episodes

You may find that you have warning signs of fainting, such as nausea or lightheadedness. If you notice the start of these symptoms, try a few simple tricks to stop them and get blood flowing back to the upper half of your body and brain:

  • Cross your legs at the ankles and squeeze the thighs together while tensing the abdominal muscles.
  • Interlock your finger and pull the arms in opposite directions.
  • Rhythmically squeeze a soft ball in your hand while tensing the thighs and abdominal muscles.

If you adjust your routine but continue to experience fainting after exercise, talk with a primary care provider. They can refer you to a cardiologist to see if an underlying heart issue might be the cause.

Exercise is important for our physical and mental health. It’s rare to go into cardiac arrest from exercise alone but not impossible, so it’s valuable to know how to react and help if you see someone collapse.

If you experience lightheadedness or fainting during exercise, or if you are concerned about your risk for cardiac arrest, schedule time to talk with a sports cardiologist about your heart health. Call 214-645-8300 or request an appointment online.

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Exercise is often cited as the best preventive medicine, but how much is too much for the hearts of middle-aged athletes? UT Southwestern sports cardiologist Dr. Benjamin Levine led a study, which was published in JAMA Cardiology, to find the answer.