Blacking Out While Running

Young woman jogging by road in rural landscape

Blacking out involves a sudden reduction of blood flow to the brain that results in a temporary loss of consciousness. Sudden black outs can sometimes occur during high-energy exercise activities such as running. There are several reasons why a runner might black out. Fortunately, you can reduce your risk of blacking out so you can enjoy your run.


Running when the temperature outside is too hot can cause you to black out. Direct exposure to the sun’s rays while working up a sweat can make you body feel overheated. Not drinking enough water before your run can also make you black out if your body gets too dehydrated. In some cases blacking out while running can indicate the presence of a more serious underlying medical condition. Certain heart abnormalities including narrow heart valves, thick heart muscles and abnormal heart rates can restrict your blood flow, causing you to black out.


While says that black outs are not typically dangerous, blacking out while running can potentially lead to injuries. Blacking out suddenly while running at high speeds can cause you to lose your balance and fall to the ground. Depending on your surroundings and your running speed, you might subsequently hit your head, twist your ankle or scrape your knees and elbows.

Warning Signs

Sometimes black outs are preceded by warning signs such as dizziness, nausea, sweaty palms and tunnel vision. Always remain aware of how your body feels while out on a run. This is especially important if you have blacked out while running in the past or if your doctor has already diagnosed you with a heart abnormality. If you are running and start to feel as though you might black out, stop running immediately and sit down. This will help reduce your risk of getting seriously injured from suddenly falling to the ground.


While there is no surefire way to prevent blackouts, you can reduce your risk of experiencomg a sudden blackout while running. Running indoors in the air conditioning instead of outside in the sun can help prevent your body from becoming overheated. During the hot summer months, try running on an indoor track at a local fitness center. If you must run outside during the summer, try to go running early in the morning or late in the evening when temperatures are a bit cooler. If possible, choose a shaded area where you will not be directly exposed to the sun’s rays. Drinking plenty of water before and after your run can help prevent dehydration.