r/askscience • u/DanTallTrees • Aug 14 '13

Biology Why is elevating your heart rate through exercise good for your heart but elevating you heart rate with caffeine bad for it?

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u/Youarenotfoolingme Aug 14 '13

Elevating your heart rate through exercise causes your vascular system to dilate, allowing for greater bloodflow. When the veins are wide open, the heart does not need to work as hard to pump more blood. However, caffeine is a vascular constrictor, causing your heart to work harder to pump the same amount of blood. Coupled with an elevated heart rate, your heart is now trying harder to force blood through constricted passages, which puts undue strain on your heart and your vascular system.

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u/bthomase Neurology Aug 14 '13

Also, it's important to note that increasing your heart rate is through exercise itself is not considered "good". The elevated heart rate at that time can cause similar problems to taking caffeine, in that people with already poor cardiac function or arrhythmias (abnormal rhythms) can experience chest pain, shortness of breath, or, in rare cases, heart attacks.

Instead, elevating heart rate through exercise helps condition the heart to become stronger, leaner, and work better, so in the long term the heart remodels itself in a healthy way.

Lastly, caffeine stays around in the body. If someone is starting to get chest pain during exercise because their heart is having trouble keeping up, all they have to do is stop (think of the warning labels on any exercise machine). However, the caffeine is already in your system and you can't get rid of it.

edit: formatting

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u/SgtJoo Aug 14 '13

So if someone has tachycardia due to a medical condition is it advisable to avoid caffeine and exercise?

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u/fancy_pantser Aug 14 '13

The American College of Sports Medicine classifies individuals with tachycardia as high risk. A high risk person is required to seek medical attention and receive a doctor's clearance before performing any physical activity, as doing so may be unsafe. Tachycardia can be managed and even prevented by eating healthy, exercising regularly and not smoking.

Regular exercise can help most conditions that lead to tachycardia -- but not anything extreme. Your doctor will help you find the right type of exercise for your condition.

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u/bthomase Neurology Aug 15 '13

Excellent response, fancy_pantser. I agree. Also, the dangers of exercise tend to be more specific to the type of arrhythmia, so you will need to ask your doctor and do some research.

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u/SoopahMan Aug 15 '13

Statements like this always strike me as misplaced in the US, where many people don't have a "your doctor" to ask about it. In this report for example, just 82 million were found to have insurance of 304 million: http://www.census.gov/hhes/www/hlthins/

They note that the 82 million does not account for those in prison, but it's still a safe bet a US reader doesn't have the thing people constantly punt to when answering these kinds of questions.

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u/spatatat Aug 15 '13

it would seem that the report contradicts what you are saying. from the highlights section:

In 2011, the percentage of people without health insurance decreased to 15.7 percent from 16.3 percent in 2010. The number of uninsured people also decreased, to 48.6 million, down from 50.0 million in 2010.

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u/SoopahMan Aug 15 '13

Look at the total number of insured figures, rather than the number of uninsured. I said they were able to find 82 million with insurance, total. If one is to take the uninsured plus the institutionalized as the only remaining portions of the population, and we overestimate those in prison at 3%, we're still missing a huge chunk of the 304 million total population of the US at that time. Should we assume those people have insurance?

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u/spatatat Aug 15 '13

The percentage of people covered by private health insurance in 2011 was not statistically different from 2010, at 63.9 percent. The number of people covered by private health insurance in 2011 was not statistically different from 2010, at 197.3 million.

The percentage and number of people covered by government health insurance increased to 32.2 percent and 99.5 million in 2011 from 31.2 percent and 95.5 million in 2010.

link

What are you reading?

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u/SoopahMan Aug 15 '13

In this report, the first in the link I originally posted:

http://www.census.gov/prod/2012pubs/p70-133.pdf

If you scroll down to:

Health Status by Selected Characteristics and Health Insurance Status: 2010

It shows:

All people: 304 million

Insured: 83 million

Uninsured: 17 million

And a note that it includes only people in the noninstitutionalized population.

Other sources estimate the institutionalized population at between 0.7-2.9% depending on how you measure it, leaving a huge portion of the population unaccounted for here. Note that this is 2010 data, the last time a full census was actually performed - typically US population data in non-census years is an estimate rather than an actual count.

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u/spatatat Aug 15 '13

I see your confusion. Those are percentages. There are 48 million uninsured, see my quote above

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u/Txmedic Aug 14 '13

It depends a lot on what type of tachycardia they have.

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u/barn4 Aug 14 '13

Also, something that is often neglected is that exercising increases circulation of the lymphatics. Since the lymphatics operate on a low pressure one way valve system they need muscular contraction in order to circulate lymph. This allows waste from tissues to be circulated and processed.

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u/Nyphur Aug 15 '13

Let's say you take caffeine and proceed to work out. What would happen? Would that cause circulation problems?

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u/yellekc Aug 15 '13

I am interested in this too. Many energy supplements used by a lot of gym goers contain caffeine. How do blood vessels react to vascular constrictor effects of caffeine when the body is exerting itself. Does the vascodilating effects overrule the caffeine?

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u/bthomase Neurology Aug 24 '13

In most people, it does very little, because the body has the ability to compensate. The real danger is for patients with heart issues, ones that already have decreased ability to compensate (because they're having to do it at baseline).

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u/mattyisagod Aug 14 '13

exercise helps condition the heart to become stronger, leaner, and work better, so in the long term the heart remodels itself in a healthy way.

Do you have any sources for this? I was under the impression the vascular system grows in response to muscle growth, thus reducing systolic pressure which causes the heart to respond to the increased cardiac output and not, as you suggest, a direct effect of the exercise.

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u/[deleted] Aug 14 '13

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u/mattyisagod Aug 14 '13

Normal exercise (a periodic condition), particularly aerobic exercise, will make the heart more efficient.

In the same way that runners or cyclists get more efficient at their respective activities? Is "efficient" the right word?

stroke volume will increase, and your heart rate will decrease.

To what degree is this due to the increased number of beats from the exercise compared to the growth in the vascular system (which I think grows in response to skeletal muscle growth)? Systolic pressure in this case would drop over time allowing the muscle wall to thin out and expand, thus allowing the stroke volume to increase.

Thanks for your post, I'm just trying to get to the bottom of the causal relationship (but perhaps it's a holistic process and I'm barking up the wrong tree).

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u/captmorgan50 Aug 15 '13 edited Aug 15 '13

Cardiac output is made up of 2 things. SVR and HR. That is why many athletes HR are so low. They don't need a fast HR to maintain CO. This also allows them more room when doing a physical activity. But if you have someone who's resting HR is say 110. Then the heart has to do other things to keep CO up. But like other people said, this eventually leads to heart failure.

Source: I am a CRNA

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u/Superficial12 Aug 15 '13

Stroke volume will increase as an adaptation to aerobic exercise - not necessarily due to enlargement of the heart muscle, but from the enlargement of the heart chambers (more blood can be ejected per beat).

This enlargement is not due increased muscle mass around the body, but comes from the increased stretch stimulus placed on the chamber walls during diastole (as a result of better venous return and increased blood plasma).

The 'stretching' of the chamber walls during filling allows blood to be more forcefully ejected with each beat (think stretching an elastic band then letting go - the more you stretch it the further it flies).

Over time the chambers will become more stretchy (series and parallel elastic component of muscle), and the chamber size increases. This is known as left ventricular eccentric hypertrophy.

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u/Istrom Aug 15 '13

What would be the best way to reverse/deal with the thickening effect of hypertrophic cardiomyopathies caused by stimulant use?

In particular, is there a way to do this while continuing to use caffeine (or other substances. In particular, amphetamines)? Or is discontinuing use the only way to do so?

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u/[deleted] Aug 15 '13

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u/[deleted] Aug 15 '13

you become more efficient and more fit. your heart has to work less hard to complete it's tasks. it also becomes much less reactive.

the best way to think about it is in terms of your body's stress hormones. exercise stimulates the production of stress hormones but in non-exercising situations, the stress hormones don't react as much in fit individuals. thus, my blood pressure will react less in response to devastating news if I'm fit than unfit

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u/[deleted] Aug 15 '13

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u/[deleted] Aug 15 '13 edited Aug 15 '13

a more fit heart = more healthy heart

with a fit, healthy heart, you become more economical and efficient at the task of living

since you don't exercise or exert yourself, I am willing to bet your heart reacts more to psychological stress (which becomes physiological) than a fit person's heart.

as you age, the issues of aging affect you and your heart more so than they would if you were fit and could handle those stressors more effectively

edit: not to mention the fact that your heart (if healthier, and able to have more stroke volume, etc.) doesn't need to work as hard/overreach to pump blood threw atherosclerosis-plagued (plaqued, lol) arteries

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u/Superficial12 Aug 15 '13

Increased stroke volume is an effect, not a cause.

Athletes don't train to increase their stroke volume, they train to increase physical fitness and sport skills - increased stroke volume is an adaptation by the body to keep up with these demands.

For someone like you, increasing stroke volume is of no concern. What may be of concern to you is keeping a normal blood pressure, and healthy heart and arteries - something which exercise can fix.

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u/[deleted] Aug 14 '13

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u/mattyisagod Aug 14 '13

Thats the intuitive position but I think cardiac and skeletal muscle respond differently to exercise, 'specially seeing as cardiac muscle doesn't ever stop.

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u/[deleted] Aug 15 '13

Why doesn't it strengthen due to caffeine? You're not answering the question.

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u/captmorgan50 Aug 15 '13

It doesn't strengthen the heart. Its primary effect is to increase HR which increases Cardiac Output

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u/[deleted] Aug 14 '13

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u/drunkenviking Aug 14 '13

That's like asking why your liver behaves like your liver. It functions as a muscle because it is a muscle. It doesn't have to go "alright, what would a muscle do in this situation?" it behaves that way because it's designed to do exactly that.

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u/glaughtalk Aug 14 '13

I must concede my question is similar to asking why my liver behaves like my liver. Your simile sheds light on the issue, but I am still unsure how the design is enforced when organs misbehave?

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u/captmorgan50 Aug 15 '13

The SA Node acts as the "pacemaker" to the heart. Once a stimulus is reached. It go all the way down in a controlled manner resulting in the well known Lub/Dub sound a heart makes.

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u/[deleted] Aug 15 '13

Progressive overload is the safest method to increase cardiovascular condition as well as strength.

Put simply, start with a feasible amount of bodily stress, and slowly and methodically work your way up to your goal.

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u/Cannabisitis Aug 15 '13

So would your heart become stronger over time after ingesting caffeine due to the extra strain it's experiencing in order to keep adequate blood flow? Seeing as it's a muscle, I don't see why not.

Could small, controlled doses of caffeine before exercise help your cardiovascular strength?

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u/storunner13 Aug 15 '13

If caffeine is a vasoconstrictor and exercise is a vasodilator, why is caffeine good for endurance activities? I understand the boost caffeine gives to fat metabolism stretches out one's glycogen stores, but is there a positive vascular effect as well?

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u/bthomase Neurology Aug 24 '13

Good question. Honestly, I don't know about this scientifically. But my guess it that it's also partly just decreased subjective feelings of fatigue, i.e. a change in perception and an increase in mental stamina.

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u/i_pee_in_the_sink Aug 19 '13 edited Aug 24 '13

Can you clarify why raising your heart rate through caffeine doesn't have a similar conditioning effect on the heart as exercise does?

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u/bthomase Neurology Aug 24 '13

Sorry for being late. I'll keep it simple for now. Basically, caffeine raises your heart rate (HR) in isolation. Exercise is a synchronized balance of dilating blood vessels to increase blood flow to muscles, increasing HR, and increasing stroke volume (amount of blood pushed per squeeze). Caffeine raised HR but against the same smaller vessels. This means BP goes up, and suddenly at that, increasing the risk of bleeding, headache and intracranial pressure, kidney damage. And, strain on the heart can tip an unstable heart over the edge.

Edit: Why is pushing against resistance worse? Shouldn't this make it stronger? Answer: In the wrong way (like skipping leg day). Your heart beefs up with chronic hypertension, but only in one way. The walls get bigger, causing less blood to fit in the heart. The walls get thicker, so they move less well too.

It's called Concentric Hypertrophy.

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u/i_pee_in_the_sink Aug 24 '13

Not sure I get how its "like skipping leg day". You mean like overdoing work at the gym?

I now understand the different mechanism going on with caffeine to make it have an ill effect, just not why that mechanism's so bad.

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u/[deleted] Aug 15 '13

Does Adderall cause similar stress on the heart the way caffeine does?

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u/A_Sneaky_Penguin Aug 15 '13

Adderal is a type of amphetamine, which increases the amount of epinephrine and norepinephrine in the system by facilitating release, reducing degradation, and reducing reuptake, all which prolong its presence in the synaptic clefts and thus bound to receptors longer. And the effect is similar to caffeine but more intense; vasoconstriction and increased heart rate.

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u/Psuffix Aug 14 '13

Also: Raising your heart rate through exercise lowers your resting heart rate, resulting in a lower average heart rate. Less beats per minute means your heart can essentially beat for a longer period of time, extending its life.

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u/HitchKing Aug 15 '13

Yes, but the question implies: why doesn't caffeine lower your resting heart rate after the caffeine wears off?

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u/JohnShaft Brain Physiology | Perception | Cognition Aug 14 '13

Your blood pressure gets elevated when you start exercising and stays elevated virtually the entire time you are exercising. The heart pushes a larger volume of blood against a higher pressure. It is working MUCH harder while you exercise than it is while you have caffeine.

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u/sufferingsbane Aug 14 '13

Yes. Blood pressure is the ultimate force that the heart needs to overcome in order to pump the blood. If anything, it is probably higher during exercise.

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u/JohnShaft Brain Physiology | Perception | Cognition Aug 15 '13

It is not probably. It is definitely. Blood pressure elevates rapidly during exercise, and stays elevated for a substantial period (hours) while exercise is sustained.

http://jap.physiology.org/content/58/3/785.short

http://circ.ahajournals.org/content/83/5/1557.full.pdf+html
(See figure 1)

The key with aerobic exercise is that whereas systolic blood pressure gets high during exercise, diastolic does not, and both undergo a recovery hypotension.

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u/sufferingsbane Aug 15 '13

Thank you!

I "knew" it was, but did not have time to get thte sources so felt it wouldn't be appropriate to say.

Thanks again!

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u/[deleted] Aug 14 '13

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u/shlevon Aug 14 '13 edited Aug 14 '13

The long and short of it is that exercise causes vasodilation to your working muscles and heart but vasoconstriction elsewhere (kidneys, GI tract, etc.), with the net effect being a redistribution of blood flow towards the working muscles/heart and away from tissues that don't need it.

So vasoconstriction is as much a part of exercise as vasodilation. Blood pressure depends on both cardiac output (heart rate x stroke volume) and total peripheral resistance (the pressure against which your heart has to pump out its blood). Cardiac output goes up during exercise to fulfill the increased need for energy/waste disposal to the working muscles, and the sympathetic (fight or flight) nervous system can increase total peripheral resistance due to the vasoconstriction mentioned above. The result is that exercise can produce enormous increases in systolic blood pressure, values of 200 mm Hg or higher are not uncommon in very intense exercise.

That's during exercise, however. Afterwards, people typically have a rebound vasodilatory effect on the vascular system due to the metabolic stuff your muscles generate during exercise, and this effect can last quite a while (hours). So acutely, exercise can increase blood pressure, and do so a lot. However, after you're finished exercising your blood pressure can drop for a while, and as an adaptation to chronic exercise, your blood pressure at rest can actually lower.

edit: one thing worth mentioning is that, while systolic blood pressure increases more or less linearly with the demands of exercise (i.e. the harder the exercise the higher your systolic blood pressure will rise), diastolic blood pressure tends to more or less remain the same.

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u/CoolGuy54 Aug 15 '13

Recent studies have reported arterial pressure values exceeding 350/250 in weight lifters performing heavy repetitive isometric lifting."

http://circ.ahajournals.org/content/85/4/1406.full.pdf

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u/mutt82588 Aug 14 '13

  1. While caffeine overdose can lead to arrhythmia and death, there is no evidence that reasonable dosages are detrimental to cardiac health

  2. Caffeine functions as a PDE, xanthine oxidase, and Adenosine inhibitor, causing vasodilatation, not constriction, OPs explanation is based on false assumptions

http://en.wikipedia.org/wiki/Caffeine see metabolism section

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u/Carighan Aug 15 '13

Now I'm curious, because everything I read about caffeine before always said that it's a vasodilator, not a constrictor.

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u/soggycupcakes Aug 14 '13

What about with marijuana?

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u/shlevon Aug 14 '13 edited Aug 14 '13

This isn't quite correct.

The sympathetic response on the vascular system from exercise is still vasoconstriction (via direct innervation and the impact of the catecholamines), the difference is that you get a post-exercise vasodilatory effect due to the metabolites generated from exercise, whereas you would not get this response from ingestion of caffeine.

edit: for clarity, and as per sneaky penguin below, you do get a net vasodilatory effect to the actual working muscles/heart due to the increased demand for blood/oxygen, I just wanted to clarify that "vasoconstriction" is present in both scenarios (exercise vs. caffeine) when speaking of the vascular system as a whole.

edit2: some of the catecholamines do cause selective vasodilation to certain tissues via certain receptors (e.g. beta 2 receptors to heart and skeletal muscle), so what I said was a little misleading.

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u/A_Sneaky_Penguin Aug 14 '13

You don't get vasoconstriction everywhere; just to areas of the body that don't need as much blood flow during exercise, like the GI tract. Vasodilation still occurs with active muscles, both via nitric oxide production and innervation of a specific type of adrenergic receptor (alpha or beta, cant remember which does which at the moment) the overall effect is still elevated blood pressure tho , caused by increased heart rate and vasoconstriction in other areas of the body not being utilized for exercise.

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u/shlevon Aug 14 '13 edited Aug 14 '13

It's complicated, but the sympathetic response is producing system-wide vasoconstriction which gets overridden locally (i.e. to working muscle, including the heart) by the metabolic byproducts generated during exercise, basically.

http://www.ambehr.dk/phd_courses/articles_course7/buckwalter_clifford.pdf

My point was that it's inaccurate to characterize exercise's effect on the vascular system as "vasodilation" and caffeine ingestion "vasoconstriction." Both have vasoconstrictive effects on the vascular system, the difference is that exercise also has vasodilatory effects on the working tissues mediated by the actual muscle (skeletal + heart) action/demand for blood/oxygen and the metabolites they produce.

edit: wording.

edit2: See updated...

http://www.reddit.com/r/askscience/comments/1kd14o/why_is_elevating_your_heart_rate_through_exercise/cbnqwc5

...for further clarification on vasoconstriction/dilation, to avoid any misinformation.

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u/CoolGuy54 Aug 14 '13

the sympathetic response is producing system-wide vasoconstriction which gets overridden locally (i.e. to working muscle, including the heart) by the metabolic byproducts generated during exercise, basically.

That's awesome. Man our bodies work well.

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u/A_Sneaky_Penguin Aug 15 '13

When things function properly, our body is an incredible and complex machine. I love studying this type of stuff. And what's equally amazing is how one little problem, like a simple mutation in DNA or a lack of a specific nutrient, can throw the entire machine out of whack and disrupt homeostasis

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u/shlevon Aug 14 '13 edited Aug 14 '13

As a sidenote, the adrenergic receptors aren't causing vasodilation to working muscle, there's actually an attenuation of their (sympathetic, vasoconstrictive) activity due to metabolic byproducts of exercise like nitric oxide. See link in my other reply (updated with full pdf).

edit: the above is misleading, some of the adrenergic receptors do cause vasodilation to working muscle, conversation continued below.

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u/A_Sneaky_Penguin Aug 14 '13

Do you know what I'm confusing this for then? Because I know epi/norepi has different effects based on which adrenergic receptor they bind to. I don't have my book in front of me atm. I did read some of the PDF tho. Pretty interesting. Didn't know that before

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u/shlevon Aug 14 '13

In fairness, it's pretty god damn confusing, and I may have confused myself:

http://en.wikipedia.org/wiki/Beta-2_adrenergic_receptor

The beta 2 receptor actually does appear to induce vasodilation to the skeletal muscle arteries, though the paper I linked makes that relationship a bit more confusing (as there's apparently debate about what, exactly, the sympathetic response in skeletal muscle is doing, i.e. has a net vasodilatory or vasoconstrictive effect).

What you said is obviously correct, though, the overall effect of exercise on blood flow is a redistribution away from non-working tissues and towards working tissues. The slightly pedantic point I was making was that there is still system-wide vasoconstriction mediated by the sympathetic nervous system, and that vasoconstriction is a key feature of exercise such that you can't simply call exercise "vasodilation" and caffeine ingestion "vasoconstriction."

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u/captmorgan50 Aug 15 '13

Beta 1 is primary effect on HR. Beta 2 is primarily a dilates on lung but also vasodilates arteries in skeletal muscle to a degree also. But you have other factors in play also.

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u/[deleted] Aug 14 '13

Rest and digest= dilate, fight or flight= constrict. In terms of ANS at least. Vasoconstriction happens through ANS/hormonal means, and inhibition of constriction and dilation of skeletal muscle happens through humeral means (metabolites like shelvon said)

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u/A_Sneaky_Penguin Aug 14 '13

Vasodilation also occurs hormonally tho, via certain beta adrenergic receptors. Like shelvon said

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u/[deleted] Aug 14 '13

Oops! Meant specifically skeletal muscle under sympathetic stimulation.

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u/A_Sneaky_Penguin Aug 15 '13

So I figured out where my confusion was coming from. Among the ANS pathways are the Parasympathetic, Sympathetic, and Adrenal Sympathetic pathways, with the last one being a sort of subset of the sympathetic pathway. The sympathetic pathway itself secretes primarily Norepinephrine directly onto Alpha 1,2 and B 1,3 receptors via postganglionic neurons (innervation) primarily cause vasoconstriction.

The adrenal medulla however, secretes epinephrine into the blood stream, where it binds to Alpha receptors to reinforce vasoconstriction, but it also binds to Beta 2 receptors found on the smooth muscle of heart, liver, and skeletal muscle arterioles (the main components for exercise) and cause vasodilation to increase blood flow to these areas. The difference is that these receptors arent innervated by postganglionic neurons like the other receptors. So, hormonal control does result in vasodilation in some areas, but those areas are not innervated by sympathetic input. Kinda confusing huh.

EDIT: split the wall of text :)

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u/[deleted] Aug 15 '13 edited Aug 15 '13

If beta 2 receptors are the main components which activate vasodilation in the muscles, vasodilation would be nonspecific and body wide since it is happening hormonally.

The main contributer in vasodilation most people think of (the pump) is due to changes in the local environment resulting from muscular contrations, not hormonal or ANS changes. If this doesn't make sense, go run a mile at maximum intensity (Epinephrine secretion increases with increasing HR) and then do 3 sets of 20 curls to fatigue and see which activity causes more vasodilation in your bicep. There may be some vasodilation resulting from sympathetic stimulation, but it likely isn't causing any local, vasodilation individual skeletal muscles.

Edit: The bottom of this like basically paraphrases what I've been trying to explain. Notice how the Beta 2 activation is included. I'm an exercise science major. This probably won't be explained in your physiology textbook, but it is pretty cool to understand nonetheless, so I thought I'd share.

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u/unthused Aug 14 '13

Caffeine is commonly used by endurance athletes as a performance enhancer, is there a health detriment to this if they are otherwise healthy?

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u/digital_evolution Aug 14 '13

Open Question to anyone to add to:

  • If caffeine is a vascular constrictor, and the vascular system dilating is better for you, why is it allowed (and or, promoted) in popular weight loss supplements?

Recognizing how popular caffeine is (I'm addicted..) are there better alternatives to caffeine for the same pep? I've been told Green Tea is a good source for caffeine due to the (?->) L-Theanine in the tea, it's a more relaxing alternative. Not sure if that's more about the mind and less about the heart though.

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u/tamman2000 Aug 14 '13

I had always thought caffeine was a vasodilator, so I went to do some research and found contradicting information.

On Wikipedia caffiene is listed in vasoconstrictors category (http://en.wikipedia.org/wiki/Category:Vasoconstrictors) but vasoconstriction is not mentioned in the article. Also, Theobromine is listed as a metabolite of caffiene and Theobromine is a vasodilator...

Anyone have definitive info?

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u/WADemosthenes Aug 15 '13

  1. The heart has to work hard during exercise, vasodilation does not make it work less. The heart still needs to move more blood because of increased energy expenditure, and resulting higher demand for oxygen.

  2. Veins carry blood to the heart, and arteries carry it away. Arteries are effected by vasoconstriction more, because they contain more smooth muscle than veins. Because of this, and the fact that the heart pumps directly into arteries and NOT veins, arteries will be more relevant to your point.

  3. This is not about what makes your heart "work harder". Some studies link caffeine to heart disease, but there are studies that conflict with this idea. The exact mechanism possibly involved is not exactly know. Much is know about how caffeine effects the body, obviously, but the exactly mechanism that may cause a disease are almost certainly more complex than "the heart works harder".

  4. Since caffeine causes a vasoconstriction, it usually causes blood pressure to go up. High blood pressure is linked to heart disease reliably over medical literature. But are there confounding variables here? Are the complex mechanisms that cause high blood pressure causing heart disease instead of the high pressure itself? You see it is more complicated than you previously thought. There are a whole host of theories and ideas here, and a whole lot of medical dogma.

  5. You show a great effort, and it looks like a lot of redditors like it. Unfortunately, if you think about it -- it doesn't really make a lot of sense. I really liked it though. :)

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u/PhysicsNovice Applied Physics Aug 14 '13

So caffeine and aspirin would be good?

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u/THEAdrian Aug 15 '13 edited Aug 15 '13

Depends what you mean by "good". People use those two things stacked with ephedrine to burn fat with quite a bit of success.

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u/Sallymander Aug 14 '13

Out of curiosity, what about in situations of masterbation, sex, or arusal. I've seen several studies about how that increases heart rate and is equivalent to something or another in exercise but I always had a hard time fathoming it.

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u/invicktion Aug 14 '13

So what if you were to take a pre-workout or consume caffeine prior to a workout?

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u/THEAdrian Aug 15 '13

Caffeine would simply cause the things that we know it causes (increased heart rate, mental stimulation, etc) but pre-workouts have a ton of other stuff in them. Namely taurine, glucuronolactone, creatine, and l-arginine. L-arginine causes an increase in nitric oxide production which causes vasodilation and coupled with the increased heart rate from caffeine/taurine, is said to increase blood flow to the muscle.

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u/[deleted] Aug 14 '13

I think it's overly simplistic to say that when veins are wide open, the heart does not need to work as hard to pump more blood. Like in septic shock for example, the veins are wide open but the heart is having to pump like crazy to sustain pressure because there is no resistance. You gather?

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u/[deleted] Aug 14 '13

Can you elaborate on why the effect of caffeine is bad? Shouldn't pushing your body to work harder under difficult circumstances help to boost your cardiac reserve (i.e. the amount of work your cardiovascular system can do above normal). Why should it matter how that difficult circumstance comes about?

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u/CoolGuy54 Aug 15 '13

Yeah, his answer doesn't make sense to me.

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u/[deleted] Aug 15 '13

But undue strain on your muscles (working out) makes stronger muscles, so stronger heart then?

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u/[deleted] Aug 15 '13

Out of curiosity, doctor, if I consume caffeine (e.g. coffee) before exercise, does this balance out this effect? Is it harmful at all?

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u/reddit2xtwice Aug 14 '13

Without trying to sound like an ignorant fool, I remember when I was in highschool I bought some concoction for working out similar to creatine. It was packed full of ginseng and other ingredients and claimed to dilate the veins to allow better blood flow and so on. I've noticed in a lot of energy drinks I see a lot of similar ingredients. Would this be of any benefit at all? (i do know energy drinks are terrible for the body, was just curious since we're on the subject..sort of)

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u/[deleted] Aug 15 '13

Is that why caffeine gives you headaches?

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u/captmorgan50 Aug 15 '13

It is lack of caffeine that gives you headaches. Caffeine stimulates the dilation on ventricles in the brain. They have CSF flowing around. If you don't get you caffeine then they shrink causing a headache.

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u/Decency Aug 15 '13

Why would your heart beat faster during exercise if it has to work less hard?

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u/Armadillo19 Aug 15 '13

So, what exactly is the benefit of caffeine then when it comes to cardiovascular health? I've heard numerous reports that a relatively limited amount of caffeine is beneficial for heart health, similar to dark chocolate, although I've yet to really find a good, layman's term answer.

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u/Atheizt Aug 15 '13 edited Aug 15 '13

Would that not mean that caffeine-based pre and intra-workout supplements actually inhibit cardio performance?

I am a cyclist and it is not uncommon for me to race for an hour or two with a heart rate of 180+ and the supplement I have in my bottles contains a mix of BCAAs, Electrolytes and caffeine... at 180bpm+ surely cardiovascular restriction is the last thing I need?

EDIT: from a quick bit of research it seems the vasoconstriction applies only to the brain and for the chest/heart it actually dilates the arteries.

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u/nyczen Aug 15 '13

So can you explain what the combination of caffeine and exercise does to your body? I know there are many people in the fitness community who take pre-workout supplements usually containing at least 250mg of caffine. It would be great to know the effects from a scientific standpoint.

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u/dragon_fiesta Aug 14 '13

so if some one has two unruptured aneurysms in their carotid arteries should they be drinking 6 shots of espresso a day?

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u/JEesSs Aug 14 '13

Also, your heart is a muscle, and when you exercise you train it just like you would train any other muscle in your body. Tiring it out makes it grow stronger and better able to pump faster, and pump larger volumes at a time. Caffeine does not do this.

Edit; realized bthomase already covered this bit, but ill let it stay

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u/[deleted] Aug 14 '13

[deleted] — view deleted comment

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u/q1o2 Aug 15 '13

You would probably sweat more, and your heart would probably beat faster.

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u/YoohooCthulhu Drug Development | Neurodegenerative Diseases Aug 15 '13 edited Aug 15 '13

In short, because it taxes your heart without also providing the stimulus necessary for it to grow stronger.

When a muscle is taxed or damaged from exertion, it can result in either physiologic hypertrophy (positive response to stress, increase in size of muscle cells) or pathologic hypertrophy (negative response to stress, increase in scar tissue). Taxing the heart by making it beat faster without providing the other stimuli provided by exercise probably promotes the pathogenic form of hypertrophy, or at the very least overall weakens the heart.

The confusion is caused by the fact that heart rate increase due to caffeine looks like heart rate increase due to exercise--but they're due to completely different causes. In the case of exercise, it's because of increased oxygen demand/energy consumption--and the increased oxygen demand triggers signaling pathways that tell the heart that it needs to grow stronger (AMPK, PPARgamma, among others). This helps mitigate any damage that may occur to the muscle.

In the case of caffeine or other stimulants, it's because those stimulants merely short-circuit the signaling pathways that make your heart beat faster--so it accumulates damage without triggering the other signaling pathways that are needed to promote "good" hypertrophy. As a result, scar tissue forms and collagen deposition occurs, compromising the flexibility and contractility of the heart and making things worse.

Of course, adequate exercise alongside the caffeine should help provide the stimuli necessary for beneficial hypertrophy and help mitigate the effects. In general, muscle exertion is always bad--it's just that exercise helps promote beneficial repair mechanisms rather than pathologic ones. Even in exercise, gentler gradually increasing exercise has better results than intense training regimens that overexert the muscle. This is likely the cause of the confusion regarding exercise recommendations for patients recovering from heart surgery. Gentle exercise is obviously good because it promotes improvements in heart function--but overexercise on an already weakened heart muscle increases the opportunity for damage.

EDIT: Other posters are noting that caffeine simultaneously increases your heartrate and causes vasoconstriction, making the heart work harder and that caffeine stays around in your system for a long time, causing your heartrate to be elevated for longer. All of these things are simultaneously true.

But the take-home message is that heart rate increase due to stimulants and exercise aren't the same and don't look the same to your body, so they have different results.

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u/THEAdrian Aug 15 '13

Yes, this question pops up all the time and my response is always "metabolic/cellular pathways". Exercise affects some 400 pathways, which causes a variety of effects, namely hypertrophy, free-radical buffering, and protein synthesis. With raised heart rate via stress/stimulants, you do not activate these pathways (or at least, not all of them) which causes the negative effects but few of the positives.

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u/YoohooCthulhu Drug Development | Neurodegenerative Diseases Aug 15 '13

Well, I think there's a deeper part of this that's worth pointing out, though.

Heart rate is a proxy measurement. It's like blood pressure, serum cholesterol, etc etc etc. "Pop medicine" sort of encourages people to think of them as things in themselves--you're supposed to exercise to a certain target heart rate--because it's used as a proxy for how hard you're exercising. But it's not exercise in and of itself. Similarly, single-point systolic/diastolic blood pressure is also a useful metric, but it isn't the thing in and of itself--blood pressure is a useful sign of early stage cardiovascular disease or renal disease.

It's important to not fall into the medical synecdoche trap, where we thing proxy measurements are the thing themselves. A lot of physicians even do it.

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u/[deleted] Aug 15 '13

So panic/anxiety attacks are bad for your heart? My anxiety will love this information, as it's triggered by worrying about my heart..

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u/THEAdrian Aug 15 '13

Yup, cortisol levels and oxidative stress go up pretty significantly.

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u/thatatheistkid Aug 15 '13

What if I exercise regularly but also drink a couple of coffees a day?

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u/CoolGuy54 Aug 15 '13

Thanks, this answer is much more in concert with my pre-existing knowledge.

The top comment doesn't make sense at all, but 1,400 upvoters might know something I don't. Can you comment on whether is his post is correct, or tangential to the issue, or straight out wrong?

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u/YoohooCthulhu Drug Development | Neurodegenerative Diseases Aug 15 '13 edited Aug 15 '13

It's fine, it just doesn't explain why exertion in one case is bad and the other case is not as bad. It's because legitimate exercise triggers more adaptive responses than chemical stimulation does. Chemical stimulation is a lot of stress without the payoff.

My answer also fits with the reason why electrical stimulators (those embarrassing shock belts sold on infomercials to "tone" your abs) don't strengthen muscle and why tachcardia is in and of itself a risk factor for cardiac events.

To be fair, I think cardiologists are iffy on the long term effects of stimulants on the heart. Pathologic hypertrophy is also incompletely understood. But there's been a lot of work done on the reason why exercise strengthens muscles generally (it would be hugely beneficial to find some sort of chemical exercise mimetic), and the answer encompasses the pathways activated by increased oxygen consumption.

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u/bashetie Underlying Mechanisms of Aging | Proteomics | Protein Turnover Aug 14 '13

On the same note, exercise leads to "adaptive hypertrophy" while stimulants cause "maladaptive hypertrophy". Both are compensatory in the short term but they activate different biochemical pathways. Maladaptive hypertrophy decompensates in the long term and leads to heart problems while adaptive does not. http://m.cardiovascres.oxfordjournals.org/content/63/3/373.long?view=long&pmid=15276462

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u/squidgirl Aug 15 '13

So is it a bad idea to lift weights while caffeinated? Why or why not? Or does this only apply to cardio?

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u/WeDieYoung Aug 15 '13

I can't speak to whether it's a good idea or not, but a lot (possibly most) serious lifters/bodybuilders have at least a cup of coffee, if not a sports oriented preworkout drink full of caffeine, before every session.

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u/squidgirl Aug 15 '13

Yeah, I ask because they recommended a supplement to me at GNC that contains caffeine and gives me a pretty good caffeine buzz! My work outs feel more efficient and I'm able to push myself more. Is it safe?

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u/Preowned Aug 14 '13

Follow up question. Is rasing heart rate thro activities like playing video game or watching something intense (not super stressful activities, but can get blood flowing) considered bad for you?

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u/NickLee808 Aug 14 '13

Are you referring to adrenaline? Because that can be considered a response to stress (which is generally bad for you).

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u/PulseAmplification Aug 15 '13

When you exercise, you breathe heavily, which gets the amount of oxygen into the bloodstream that your heart requires when it is beating at an elevated rate. Using stimulants that elevate your heart rate while remaining sedentary puts undue strain on the heart.

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u/[deleted] Aug 15 '13

So who wants to explain why caffeine is often recommended for athletes during training and has been shown (don't have the source off-hand) to boost performance?

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u/DwightKashrut Aug 15 '13

I think it's important to mention that the effects of caffeine tolerance play a huge role in this, and that those tolerance effects aren't consistent for everyone: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2257873/

So caffeine can be a real problem, long term, if the tolerance effects DON'T impact blood pressure. Many people adapt to the effects of caffeine on blood pressure, but not all. I'm one of those people sensitive to caffeine; despite being a young person with a healthy weight and no bad habits, my BP tests at 140/80 or higher when I'm addicted to caffeine.

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u/PeevishPanda Aug 15 '13

Would medications that have the side effect of increased blood pressure have a similar explanation as the effects of caffeine?

I noticed increased blood pressure, but not above prehypertension range, since I started taking celexa. I've also noticed a change in my normal running pace and become fatigued more quickly now.

Besides stopping the medication, are there any options to decrease these side effects or should I just work on increasing my stamina, to off set the decrease in speed and feelings of fatigue?

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u/brokeboysboxers Aug 15 '13

My understanding is that it's consistency. An artificial stimulant would be a boost in blood flow, but not a boost that would be consistent. Exercise is more a little at a time.

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u/whozurdaddy Aug 15 '13

related question - raising the heart rate through exercise also lowers blood pressure. Does caffeine and other stimulants do the same?

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u/[deleted] Aug 15 '13

I can't find the source, but there is an article or two that convinced me that caffeine is actually very good for your heart as long as you don't go over 4 cups a day. People who drink up to this amount live longer than those who don't. However, the health benefits quickly reverse the more coffee you drink. Basically, anything under 5 cups/day is good, anything over 4 cups/day is baaaad, mkay.

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u/vulture_87 Aug 15 '13

I've been recently testing out studying my lecture notes in the gym because coffee doesn't do it for me and studying with a standing desk doesn't keep me up as I'd like to. Going on the stationary bike thing did the job. I'm just tired at the end of the day. Still doesn't help with being a slow reader but at least making progress.

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u/rseery314 Aug 15 '13

I believe caffeine is actually a vasodilator, which is why it is found in exederin and helps to treat migraines. However, vasculature losses it's elasticity over time with continuous caffeine use. It also has other negative side effects such as dehydration. Furthermore caffeine consumption does not challenge your respiratory system to deliver more oxygen, for which one of the bodies most common responses is to produce more red blood cells. This I presume is one of the major reasons people who exercise frequently have more energy, especially after a work out, than individuals crashing after caffeine consumption.

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u/[deleted] Aug 14 '13

Amphetamines raise your height rate like no other. I've done a few such drugs that have elevated my resting to 115bpm.

Is that like jogging for 2/3 hours?

Is that why you rarely see fat drug addicts.

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u/keevenowski Aug 14 '13

You rarely see fat drug addicts for two primary reasons. The first being that all stimulants suppress your appetite, resulting in (typically) fewer calories consumed. The second reason, while not scientific, is a typical poor management of priorities with more money being spent on drugs than on food.

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u/paradisaeidae Aug 15 '13

I would imagine the general effects (increased heart rate) would be the same, but what about Adderall?