Your blood pressure is higher while you're exercising at first, but it becomes lower on average as a result of exercise (in much the same way that exercise raises your heart rate during exercise, but lowers your average heart rate).

The reason is that exercise:

• Causes your body to store and carry oxygen more efficiently, by improving oxygen storage in your muscles, increasing the density of of red blood cells in your blood, and increasing the amount of hemoglobin in those red blood cells. This reduces the amount of blood flow required to support your body's operation.

• Increases the size and strength of your heart, which no longer has to work as hard to pump.

• Stretches out your blood vessels, making them more flexible to blood flow. The stiffness of blood vessels is a big part of high blood pressure, and contributes to the buildup of deposits on the sides of the blood vessels that contribute to e.g. heart attack or stroke.

When your body is storing oxygen more efficiently, your body doesn't have to "ramp up" to handle everyday tasks. You feel this as being less out of breath from small bits of exercise, like jogging for a moment to catch a bus or climbing a flight of stairs. It can also run quieter when you're stationary, because fewer, gentler heartbeats are needed to sustain your body's background oxygen usage. That reduces the overall stress on your body, and lets your body heal itself under low stress in between bouts of heavy exercise in a way that it can't if it's constantly under stress.

For example, I find about 30 minutes of relatively strenuous exercise a day drops my resting heart rate from ~100 beats per minute to ~60. Even though it spikes up to like 150 bpm during that exercise, that's only for 1/48th of the day, and it's running half as hard for the other 47/48ths. My low-fitness heart has to beat about 144,000 times a day, while my high-fitness heart has to beat 4,500 times during the exercise (using the 150 bpm number) and 84,600 times for the other 23.5 hours of the day, for a total of 89,100 beats - barely half as many.

High blood pressure leads your heart to work hard constantly, with two long-term effects:

• you get an enlarged heart, which can actually lead to less efficient beating - there's only so much room in there, so a larger heart has less room in which to beat;
• your blood vessels never get a chance to relax, so they tend to harden, meaning that the higher pressures are progressively experienced further away from your heart.

Harder, stiffer blood vessels are more prone to breaking and tearing. They're also more prone to damage that leads to clotting, but the clots don't stick as well. Your risk of strokes rises.

As time passes and your heart spends years working much harder than it was designed for, the muscle starts to degrade, so eventually you have this rather large yet, paradoxically, very weak heart that beats ineffectively. Your blood vessels are trashed all the way out to the capillaries, and between that and the ineffective beating you're not getting adequate oxygen to your extremities. the only fix we have, and it's not a good one, is total heart replacement - organ transplant.

Your blood vessels are like roads. Without exercise they are dirt roads. They get potholes, travel across them can be cumbersome and difficult.

When you start exercising, your body starts to patch up those potholes. Maybe add some cement or tar to help the roads be a bit more stable.

With lots of aerobic exercise, your roads becomes highways, well developed and cleaning moving with lots of chill traffic that doesn't cause accidents because of the conditions they are driving in.

Dirt roads don't really get potholes. Instead, this happens: https://en.wikipedia.org/wiki/Washboarding Its incredibly annoying. You have to get like a bulldozer to level it out every now and then. Your analogy still works though :D

Thank you for this breakdown.

Wouldn't your heart need to beat more forcefully to move the same volume of blood completely around your body at 60bpm than at 100bpm, though?

And are these your own actual numbers, or are people more likely to see a more modest decrease in resting heart rate, like from 70bpm to 60? 100 seems awful high for "resting"!

> Wouldn't your heart need to beat more forcefully to move the same volume of blood completely around your body at 60bpm than at 100bpm, though?

No. You don't need as much blood flow when your blood is more efficiently carrying oxygen, and it doesn't have to push as hard when it's not getting as much resistance from your arteries.

> And are these your own actual numbers, or are people more likely to see a more modest decrease in resting heart rate, like from 70bpm to 60? 100 seems awful high for "resting"!

It is high, yes. It's typical of someone with poor physical fitness, but not healthy. 60 bpm is a fairly normal healthy resting pulse. But the thrust of the explanation - that the heart does less work by having mild stress during exercise and less stress the rest of the time - stands either way.

Please read this entire message

Your submission has been removed for the following reason(s):

• ELI5 requires that you search the ELI5 subreddit for your topic before posting.

Please search before submitting.

This question has already been asked on ELI5 multiple times.

If you need help searching, please refer to the Wiki.

If you would like this removal reviewed, please read the detailed rules first. If you believe this was removed erroneously, please use this form and we will review your submission.

Ah, was just wondering because it's often at lower heart rates when I feel my heart pounding particularly forcefully, but I think my oxygen transfer may be a bit out of whack cause rona.

Will deconditioning cause your resting heart rate to go back up? Or if you're less active will you still maintain your low RHR past the point where whatever damage people think you're going to cause yourself by not pushing yourself to exercise til you drop through something like long COVID?

> Will deconditioning cause your resting heart rate to go back up?

Yeah, because your body won't keep putting in the resources to maintain the higher level of fitness.

After how long, would you say? Weeks, months, years?

And does that mean that if your RHR stays the same around 60ish, you're getting adequate cardio in to avoid deconditioning?

> After how long, would you say? Weeks, months, years?

Well, empirically, I notice it after a few weeks and have mostly reset after a few months, but this is deeper than my knowledge goes. (The rates probably vary by a lot of factors, like sex and age among others.)

Excellent, thanks! I don't have a normal control to test, so I had to ask...

I've maintained my resting heart rate over the last few months of actively trying to rest and pace myself to try and help my long COVID. This has caused much hand wringing about deconditioning from every single person (not to mention what all of their friends say!) who knew me before I got sick! Despite me telling them I'm still hitting my Fitbit (now switched to Garmin!) cardio goals, they are thoroughly convinced that deconditioning is something you'll never notice until one day you get up to make a coffee and your legs crumble into dust. Which you can then supposedly never recover from. A presumably healthy person like you, your description of deconditioning and your knowledge of your own body and what's going on inside it isn't questioned as much as...anyone within a 10 mile radius of the 'rona.

I wouldn't take my personal experiences as some sort of proof. If you're looking for guidance on your own health, talk to your doctor. (Notably, I have not, to my knowledge, had covid.)

No, I was just looking for a healthy, fit control that didn't have COVID, but also had familiarity with their own heart rate.

I'm not a healthy, fit control. Even in the more-fit of those two states I was still way overweight and not particularly fit.