Running Doc explains Runners Nocturnal Syncope (RNS)

Dear Running Doc:

I am a 45-year-old runner who has been running 40 to 50 miles a week for 30 years. I have no medical problems. Except, last week, in the middle of the night I got up out of bed to go to the bathroom and I fainted. My doctor said not to worry about it. What do you think?

Adam J., Manhattan

Thanks for the question, Adam. This is actually a very common phenomenon seen in long distance runners (more men than women for some unknown reason). This is called Runners Nocturnal Syncope (RNS).

When runners run consistently long distance their vasculature (arteries and veins) in their lower extremities become highly efficient for exercise. That means stronger arteries to pump blood to the muscles and larger veins to handle the increased blood pool within the muscles. Blood returns via the pumping of the muscles during exercise movement.

When runners get up quickly, they are destined to lightheadedness until their blood flow equilibrates with their upper body or even RNS (faint) in the middle of the night.

So, Adam, this is very common, not a medical problem, and testimony to your high level of training. Just try not to rush out of bed to the bathroom. If you have any more questions please do not hesitate to write.

Enjoy the Ride!

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Lewis G. Maharam, MD, FACSM is one of the world’s most extensively credentialed and well-known sports health experts. Better known as Running Doc™, Maharam is author of Running Doc’s Guide to Healthy Running and past medical director of the NYC Marathon and Rock ‘n’ Roll Marathon series. He is Medical Director of the Leukemia & Lymphoma Society’s Team in Training program. He is also past president of the New York Chapter of the American College of Sports Medicine. Learn more at runningdoc.com.

Want your question answered in this column? Write to running doc at runningdoc@nydailynews.com.

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