Gabe Mirkin, M.D.
Athletes and other very fit people may feel dizzy when
they rise from lying to standing because of their slow pulse rates.
Exercise makes your heart stronger so it can pump more blood
with each beat and it doesn't have to beat as often. A slow
pulse rate can be good. Since your heart doesn't beat as often, it
has more time to rest between beats. Like a low-mileage used
car, perhaps this will mean it takes longer to wear out. But a slow
heart rate can make you dizzy when you change position.
When you raise yourself from lying to sitting, or from
sitting to standing, the force of gravity pulls blood down from your
brain towards your feet and your blood can't get back to your
brain until your next heart beat. If you have a pulse rate of only
50 beats a minute, it will take more than a second between
beats. That can be enough time for your brain to suffer briefly
from a lack of oxygen, so you feel dizzy. You can even pass out
while you wait for your next heartbeat to come along and pump
blood back up to your brain.
Dizziness can also be a sign of an irregular heartbeat or
blocked arteries leading to your brain, so people who feel dizzy
when they get up should check with their doctors. If they are
athletes, chances are that they only have a strong athletic heart
with a slow rate, and all they need to do is remember to get up
slowly.
November 20, 2005