I went to the gym today, as part of my never-ending quest to lose weight and be more fit. Before I started, I used one of their automated blood pressure machines. My BP was a little bit high – about 140/90. My pulse was about 65. I did 45 minutes of cardio exercise, 20 minutes on the elliptical and then 25 on an exercise bike. Then I tested my BP again, on the same machine, and it was now significantly lower: 114/75, pulse rate about 95. I would have thought that the vigorous exercise would have increased the pressure. What am I missing? Or is there something weird going on?
IANA Doctor (or even remotely in the medical field) but I recall similar situations. Here are some thoughts: [ul]
[li]The fact that your heart rate increased is definitely normal though you don’t say how long after you exercised you measured it.[/li][li]Were you stressed or tense before starting (i.e. was your blood pressure perhaps artificially elevated)?[/li][li]Exercising can actually relax you and this may be the effect that you saw.[/li][/ul]
I would relate the experience to your doctor when you have a chance but also keep track of both heart rate and BP as you continue to exercise and see what trends (if any) occur.
Yes, I should have mentioned that I already have a checkup scheduled with my doctor next week anyway, so I will definitely ask her. I’m not asking for personal medical advice, just a better understanding of the relationship between exercise and blood pressure.
I took the second BP test in about as long as it took me to go take a drink of water from the fountain, go back to the trainers’ area, sit down and wrap my arm with the cuff. Just a few minutes.
I am generally not fond of exercise, and don’t find it relaxing, but I was not especially tense prior to the session, either.
Is it possible that just sweating a lot for 45 minutes could have lowered my BP?
I think at this point I would recommend that you review with your doctor both what has happened and what you are planning in the future. You should always get your doctor’s OK before starting on any kind of exercise program and since you have an appointment next week I would definitely make exercising a topic of discussion.
Many factors contribute to exercise programs and what is best (or worst) for you depends on such things as weight, drugs that you are taking, age, other physical limitations, etc.
Don’t want to discourage you but talk with your doctor.
I did check with my doctors – all of them – before starting my exercise program a year or two ago. The results are small and slow in coming, but are at least in the right direction. I just never happened to check the BP both before and after exercising. I was hoping that someone knew whether what I saw was an expected thing or not. No big deal.
IANA doctor either, but I would think that the following could partly contribute to your BP readings (someone please feel free to correct me if I’m way off base). If I remember correctly, at the start of cardiovascular excersize there is a decrease in blood plasma volume as the tissues absorb fluid. This could, it seems, cause BP to read lower after excersize than before.
The relationship between heart rate and blood pressure, in practice, can be fairly complicated. None of the figures you quote sound at all concerning to me, as an emegency doctor, but ask your own doctor.
Tissues need oxygen; exercising muscle needs lots of oxygen. You can get more oxygen to your tissues by increasing “cardiac output” or increasing the amount of oxygen in the arteries. Cardiac output depends on heart rate, fluid volumes, and “elasticity” of the heart muscle – a higher heart rate, to a certain point, increaes oxygen flow to the tissues. Blood vessels can dilate or constrict to change their flow levels (and “resistance”, and do this based on many factors including auto-regulation, signals from the sympathetic nervous system, and several chemical signals – kinins and prostaglandins involved with pain and inflammation, for example, can dilate blood vessels; other chemicals such as angiotensin constrict them) Blood pressure itself has two numbers that represent maximum and minimun values depending on whether the heart is pumping or taking a short break before pumping again. An average blood pressure is equal to cardiac output times resistance.
During exercise, to increase oxygen – heart rate tends to rise, you might breathe faster, blood vessels to the muscles tend to dilate so more blood can flow there. This dilation can drop the blood pressure, as can the pain and inflammation chemicals that may be produced during exercise. Exercise can be dehydrating, and lower fluid volumes – though the body can compensate for a 10-15% or so loss in fluid volumes before this would dependably drop blood pressure (a condition doctors call shock). I won’t go into lactic acid and aerobic and anerobic energy production by the muscles here.
Suffice to say, blood pressure is a complicated thing. By itself, sweating for 45 minutes and the stresses and relaxing effect of exercise only tell part of the story. In addition to the changes during exercise, the body reverses these changes in heart rate and blood pressure after exercise (a compensation effect), and when you are no longer exercising, the heart rate slowly returns to normal. Blood pressures during exercise and 15 minutes after exercise can be very different.
To summarize, exercise would usually increase your heart rate and heart “elasticity” via the sympathetic nervous system. This system also increases blood flow to the skeletal muscle at the expense of blood flow to other organs (not the brain). Blood vessels going to exercising muscles get bigger, and blood flow to muscle increases (by up to 20 times normal). Adenosine, temperature, and pain and inflammation chemicals also increase the blood flow via vasodilatation. These dilating blood vessels reduce blood pressure (pressure in a big pipe is lower than pressure in a small one). Pumping muscles and vein constriction increase the flow of blood back to the heart and helps maintain some blood pressure. The increase in cardiac output (heart rate times stroke volume)often outweighs the decrease in resistance; if this is the case the systolic blood pressure may rise while the bottom number may fall or only rise slightly. Exercise has to be quite heavy for “stroke volume” to raise the cardiac output significantly. Since blood pressure is cardiac output times resistance, the pressure may also drop of the decrease in resistance outweighs the increase in heart rate.
During recovery from exercise, blood pressure often falls since the effect of the local metabolites (pain and inflammation chemicals) lasts longer than the increased heart rate, which slowly returns to normal after recovery due to the baroreceptor reflex. It’s just that easy. 
Aha! Thanks much, Dr. Paprika.
So what may be happening (to put it in my words) is that the blood vessels are getting slightly larger to permit increased blood flow – thus the reddened skin color I notice – which can tend to lower the BP – and this effect can remain for a while after exercising.
Again, just to reassure, I was not asking for personal medical advice, just an explanation of the mechanism, which you have so kindly provided.
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MLS, as far as the “not liking exercise” goes…keep at it. If you can make a mental effort (and it will be a large effort) to go to the gym on a regular schedule for 3 months, you will find that you enjoy going, and “miss” it when you don’t.
I have no idea what you look like (you may be speed-training for the local marathon, for all I know), but I found that when I started working out (weights, cardio, boxing class), I felt so much better stress-wise, body-wise, and in nearly every other -wise that I would be crushed if I had to give it up now (injury, etc.).
Make it a habit, and then defend it against all comers. You’ll thank yourself later.
-Cem
Thanks for the encouragement, Cym. I will probably always hate the gym. I hate getting all hot and sweaty, the boring, repetitive nature of the process and the constant noise. Yes, I do wear headphones to block that out, but they only add to the sweatiness factor. The only thing I like is that this “fitness center” has a pool, which I do enjoy – you don’t get hot and sweaty while swimming. So if I do time on the rower, or the bike, or the elliptical, and/or some weight machines, I reward myself with as many laps in the pool as I can handle, followed by a soak in the hot tub/therapy pool.
To put it in perspective, I’m at best middle-aged, have bad knees (due to injury), and spinal arthritis, which means I can’t engage in any high-impact activity. I have developed much more endurance, and have lost maybe 5 pounds, which sounds good, except that it has taken a couple of *years * to do so. When I was employed, my schedule was to go 3 times a week. Now that I’m out of work, I’m trying to go more often – a few weeks in August I went almost every day.