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Athletic Training

Morning workout



Is it bad for me to work out right after waking up in the morning? I was told that our blood is thicker right after waking up and that it could put extra stress on my heart (I have no heart conditions) if I were to exercise immediately after getting up in the morning. I don`t think this is right. Who is correct?


The thickness (viscosity) of blood doesn't change much under normal resting circumstances, although your blood DOES become thicker during vigorous exercise due to shifting of water out of the vessels and into your working muscles.  In almost all cases, this is not a problem.  The exception has been if you are taking erythropoeitin (e.g. Procrit), a drug that causes you to make more red blood cells (typically used with chemotherapy and anemia patients).  In elite professional cyclists, it has been linked to heart attacks due to thickened blood.

When you wake in the morning, you will be a little bit dehydrated relative to your hydration status at going to bed because your kidneys will remove some of the water from your blood while you sleep.  This is why your bladder is typically full enough on waking that you have the urge to urinate. 

The question is... Do you remove so much water that your blood thickness is going to stress your heart?  The answer is no for almost everyone.  Your heart is capable of handling the stress of exercising, even if you are a little bit dehydrated.  You can estimate how dehydrated you are by the color of your urine.  If it is the color of lemonade or lighter, your hydration is typically fine.  If it is darker, like honey, you are probably a little dehydrated. 

In either case, I would certainly recommend that you drink some water in the morning before you exercise.  In fact, one of the recommendations from the National Athletic Trainers Association's Position Statement on Rehydration with exercise is that you drink 7 - 10 ounces of water 10 - 20 minutes before you exercise.

Now the caveat... if you have heart disease, you might not be able to tolerate the stress from mild dehydration in the same way that others do.  If this is your case, you need to discuss this with your cardiologist who is in a position to have specific knowledge of your situation and your limitations.|

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Response by:

Mark  A Merrick, PhD, ATC Mark A Merrick, PhD, ATC
Associate Professor
School of Health and Rehabilitation Sciences
The Ohio State University