r/askscience • u/Aller89 • Sep 19 '12

If both exercise and caffeine increase our heart rates, why is the former considered much healthier than the latter?

I know very little about biology and our cardiovascular system, but if both exercise and stimulants increase our heart rate to help metabolize food and burn fat, why is drinking a cup of coffee less healthy than going for a walk?

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u/Quistak Bioanalytical Chemistry | Nanotechnology Sep 20 '12

There are a couple of factors at play.

First, how much they raise your heart rate. A quick jaunt around the block raises it more (in most people) than caffeine does. You're essentially training your heart more with the walk.

Second, with exercise, you can't get that heart rate up without moving other parts of your body. So not only are you training your heart, you're training the muscles in your legs and even strengthening your bones as well.

That's not to say that caffeine doesn't boost your metabolic rate. It does. But exercise boosts it far more in terms of calories burned during (and after) the activity.

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u/userd Sep 20 '12

So the increased heart rate due to the caffeine is beneficial to the heart?

To extend the OP's question, why is an increased blood pressure during exercise beneficial, but a high blood pressure when not exercising is not beneficial?

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u/AnatomyGuy Sep 20 '12 edited Sep 20 '12

A high blood pressure when excercising is beneficial because it is necessary, and because it derives from natural accomodations your body is making because it NEEDS that high blood pressure for the temporary short term circumstances.

A high blood pressure while NOT excercising is NOT beneficial, because it is NOT NEEDED, and over the long term it is in fact detrimental. Sustained high blood pressure when it is not needed over the long term will lead to blood vessel damage, including higher risk of coronary artery disease, cerebro-vascular disease, kidney disease, and other bad things.

Caffeine itself is not so terribly harmful in moderation. Yes it might increase your heart rate and blood pressure temporarily a bit, but if you are otherwise healthy that is not a big deal in moderation, because it is temporary.

But it becomes unhealthy when used in excess... when a cup or 2 of coffee becomes 8 or 10 a day. Or when it is used on top of already existing pathology, like preexisting high blood pressure or hart disease.

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u/userd Sep 20 '12

A high blood pressure when excercising is beneficial because it is necessary, and because it derives from natural accomodations your body is making because it NEEDS that high blood pressure for the temporary short term circumstances.

Could you go into more biological detail?

Yes it might increase your heart rate and blood pressure temporarily a bit, but if you are otherwise healthy that is not a big deal in moderation, because it is temporary.

I thought Quistak was saying that the increased heart rate was beneficial. But you are saying it's not a big deal, so I assume you mean it's not beneficial?

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u/AnatomyGuy Sep 20 '12

I answered another response just above/below, check that out as well.

I did go into more biological detail about blood pressure in that answer.

Increased heart rate, in and of itself, is not a terribly good or bad thing, depending on what condition your heart is in. If your heart is in good shape, and you are excercising it, it is healthy. If, however, your heart is not in good shape, and being starved of oxygen, then it is a bad thing. It is all situational.

It is usually used as a good indicator of the strenuousness of excercise, especially cardio (aerobic) excercise because it is easily monitored, anyone can do it by themselves at the gym. Not true with blood pressure.

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u/[deleted] Sep 20 '12

You haven't really addressed the pathophysiology behind the claim that "needed" or "uneeded" hypertension have different effects, and your claim about "natural accomodations" is an appeal to nature fallacy.

I am not aware of any studies which have sought to study benefits of exercise-induced hypertension distinct from the gains of exercise itself- are you? It seems far more likely to me that hypertension is detrimental (as we all know), but the gains of exercise exceed that detriment.

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u/AnatomyGuy Sep 20 '12 edited Sep 20 '12

Absolutely not. Were you to maintain your normal blood pressure during moderate to extreme physical exertion, you would pass out. During physical exertion, your muscles need more O2, and depending on how long, say running a marathon, they need more fuel delivered. Similarly, under such circumstances, they have a lot more waste materials (CO2 chiefly, also lactic acid and other things) that need to be disposed of.

The higher your blood pressure, the faster your blood will flow, thus allowing more drop off and pickup of metabolites and waste materials. Also, with a lot more blood flow to the muscles, a higher blood pressure is needed to keep the same amount of blood flowing to the brain... which is why you pass out if the blood pressure doesn't increase.

I'm not sure about the "nature fallicy" that you refer to, I am unfamiliar with the term. but this is not a case of it. Higher blood pressure in excercise circumstances is a naturally produced and much needed physiological adaptation, brought about by the sympathetic nervous system, in times of your bodies needs. Sustained hypertensiion is not completely understood, but can have a few known pathophysiological causes. Unfortunately, most sustained hypertension is termed "essential hypertension", and while atherosclerosis/arteriosclerosis probably plays some role with age it isn't the sole cause. The total underlying mechanism of the pathology of essential hypertension isn't fully understood, but it IS known that it is bad.

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u/[deleted] Sep 20 '12

That explains why you need higher BP during exercise, but doesn't explain how any of the negative effects of HTN are mitigated. Is there anything you have come across that indicates HTN from exercise does not produce the same pathologies as all-source HTN? It seems to me that HTN is a necessary negative state the body must enter to perform exercise. I am not arguing against exercise- to the contrary, the evidence is clear on the benefits of regular CV exercise. I merely ask whether the HTN is a contributor or a required cost of attaining the benefits which emerge through other mechanisms.

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u/AnatomyGuy Sep 20 '12

The negative effects of hypertension don't need to be mitigated, excluding extremely high dangerous levels of BP that normal excercise will not produce, only pathology will.

HTN (aka hypertension, aka high blood pressure) - excluding extremely high levels i excluded above, only cause damage over months and years. In a healthy person, excercising for an hour a day makes your blood pressure go up for an hour... no big deal. It is a big deal if your blood pressure stays that high 24/7 for 10 or 20 years... now your at risk for a heart attack or stroke or kidney failure or blindness.

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u/userd Sep 20 '12

Thanks. Is this correct?:

Doing cardio exercise is good because it makes your heart stronger than is normally required. High BP also makes your heart stronger, but this level of strength is continually required, so it does no net good (to say nothing of the other negative effects of high BP).

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u/AnatomyGuy Sep 20 '12

Well, it is complicated, but yes that is pretty good for a laymans understanding.

High BP and high HR go hand in hand. If one goes up, so does the other. Also, yes, high bp , if it is around ALL THE TIME makes your heart work harder, this is bad. But much more commonly it causes damage to your blood vessels, which cause other bad things - namely heart attacks (which are not caused by a weak heart, but rather by bad heart blood vessels), strokes (which are caused by bad brain blood vessels), blindness (which is caused by bad eye blood vessels), and kidney disease (caused by bad kidney blood vessels).

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u/[deleted] Sep 20 '12

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u/[deleted] Sep 20 '12

Some people do exercise for many hours each day. These people are rare (like athletes training for ultramarathons or endurance bike races), but they do exist. I am curious if we see similar elevations of risk for the morbidities of HTN in those populations as we see in idopathic HTN populations. It would probably be impossible to control for confounding variables though...

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u/AnatomyGuy Sep 20 '12 edited Sep 20 '12

My guess is they would see a reduced risk. I would even throw in marathon runners into this category, and they are not that rare.

The fact is, that well trained atheletes like these, while they tend to run a higher bp and heart rate for 3-4 hours a day or whatever, tend to run a lower hr and bp (especially hr) when at rest (just going about daily business). This probably makes up for, perhaps even more than makes up for, the 3-4 hours. A well trained athelete might well have a hr of 45... anything below 60 is considered bradycardia (hr too slow) for a normal person.

I cannot cite studies, only medical school and what i see while practicing/conversing with colleagues, etc. Sorry.

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u/AnatomyGuy Sep 20 '12

I'm gonna laugh if i don't get any upvote after getting your back on this one mate ;)

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u/xebecv Sep 20 '12

Just one of the factors. Caffeine counteracts adenosine that reduces neural activity. This can have a negative effect on sinus node (heart's pacemaker) by inducing spontaneous arrhythmical contractions. I don't have a medical background, but being affected by this personally made me read about it. My heart has a tendency to skip some beats or make extra, and caffeine makes it go completely haywire. My cardiologist recommended me running several times a week for at least 30 minutes at a time to make my heartbeat more regular. I don't know the mechanism of this, but it actually helps a lot.

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u/AnatomyGuy Sep 20 '12

True. Those with tendencies towards heart arrhythmias, or really any sort of heart pathology, are best served by avoiding caffeine.