Exercise indued hypertension

[runnertom]

Thank you for entertaining my question. I am and have been for 30 years a very heavy exerciser (56 yo male). I had CABG Feb 2003 for an LAD blockage and am now feeling at least 100%. About three years ago I had a treadmill test where it was found that I appeared to have exercise induced hypertension. BP went to 210/110 at max exertion (15 mets I believe). I had another last week that was also high in spite of the fact that my resting BP averages 110/70 without meds.
   I have thought of two possible explanations for this phenomena in me, other than being pre-hypertensive. The first would be that in the Bruce protocol, one is given essentially no time to warm up and get the small vessels in the working muscle dilated for the heavy exertion. You are into fairly heavy work within 10 minutes and the early stages are not really enough to effect a warm up.
   The second area is fluid retention. I remember reading the late running Guru Dr. George Sheehan that runners often show reduced hemocrit. The had been blamed on micro bleeding into the intestines, but later evidence showed that endurance athletes often have significantly elevated blood volume. This is apparently due to the body's compensation for extended exertion.
   I have noticed that after a workout, my BP can be very low, like 100/50 when I am somewhat dehydrated. Do you think either of the factors I mentioned could be responsible for the treadmill BP measurements? Secondly, do you think that if not, does the hypertensive effect during exercise pose a significant risk to my arteries?

[CCF-M.D.-MJM]

Good questions but unfortunately there is not a good answer to these questions.  It is true that there is a relatively short warm up time before max exertion on the Bruce protocol.  15 METs is a pretty good effort by the way, you must be fit.

Volume status does not have a huge effect on blood pressure as long as you are relatively well hydrated--assuming your kidneys work normally.  When your blood volume goes up, the body acting by way of the kidneys will increase urine production almost immediately.  

Your comments Sheehan is correct.  Runners do carry a slightly higher fluid volume and essential dilute there red blood cells to a lower hematocrit.  The problem is that no all runners have exercised induced hypertension  It is a small subset of the population.

Regarding damage to your arteries.  Your blood pressure probably does become very high until you are at peak exertion.  I trust that every work out is not done to 15 METs, so you body only sees this high blood pressure when you are really pushing your self.  I would not stop exercising because of exercise induced hypertension.

I hope this helps.

[runnertom]

Doctor,
  Based on my observations, I think it is true that the kidneys act to dump extra water as soon as the body realizes it. I have noticed more than a few times that if I do not exercise for two days in a row, I will suddenly need to urinate great quantities of clear urine for an hour or two. This never happens if I take only one day off between workouts. It is as if the body suddenly gets the idea that it is sedentary and is overhydrated based on that status.
   You are right that I don't spend a lot of time exercising at 15 mets, but probably significant time at 80 to 90%. However, if hydration status is a player I would guess that perspiration and expiration water losses fairly quickly remove the excess water.