Posted On:11/03/2005 1:22am
Style: Shuai Jiao/Boxing
What is the difference between exercise-induced heart hypertrophy, and hypertrophy caused by hypertension? Thats my main question here, but it branches off.
Why does high blood pressure increase the size and 'force of contraction' in the heart in the first place? Well, if the heart rate is constantly so high (due to high peripheral resistance), wouldn't it be overtraining the heart, so to speak? If so, why does the heart grow from this form of over working?
Thanks for your time.
Posted On:11/03/2005 10:27am
Style: One-armed flailing
I'm no health specialist, but logically, your heart is designed to beat constantly until you die. So, it's got some special muscle fibers that don't tire out nearly as easily as your skeletal muscles. Also, I'd assume they could grow and repair while still beating. As far as the high bloo d pressure thing, I think it's because your arteries and **** are blocked up with fatty fat fat and therefore are constricted. Thus, your heart has to pump harder to get your blood through the constricted pathway (think blowing a golfball through a garden hose or a gutter, which is easier?). All considered, I'm pretty sure "overtraining" your heart would be pretty difficult, and you would almost certainly feel some bad effects before a heart attack that might warn you. But don't take my word for it, I would say turn to your friend :google: .
Posted On:11/03/2005 7:14pm
Your CNS will be overworked long before you overtrain your heart.
Signs of CNS overtraining
2. Light headedness
3. Strong or irregular heartbeat
8. Unquenchable thirst
9. Muscle soreness
10. Shortness of breath
Legendary Street Fighter
Fear and bullets.
Posted On:11/03/2005 7:27pm
Exercise-induced cardiac hypertrophy is generally associated with steroid abuse or truly epic suplementation schedules, along with a supremely intense workout schedule. Your heart has evolved to move blood rapidly and efficiently, thus necessitating elasticity of the heart muscle. When someone works the heart (as with any muscle) it becomes more efficient at it's job. The muscle becomes stronger, moving more blood more efficiently. When this same individual adds a steroid or supplement that increases the growth of any muscle, it increases the growth of the heart as well. If the heart gets excessively bulky, it loses flexibility, and the increased mass of the heart muscle decreases the size of the ventricles, which limits how much blood the heart can move. Eventually, the damn thing is so muscular that it can produce incredible pressure, but no flow due to decreased ventricular capacity. Which produces tachycardia under stress. It is virtually impossible to accomplish this without chemical help; but not unheard of.
And lo, Kano looked down upon the field and saw the multitudes. Amongst them were the disciples of Uesheba who were greatly vexed at his sayings. And Kano spake: "Do not be concerned with the mote in thy neighbor's eye, when verily thou hast a massive stick in thine ass".
--Scrolls of Bujutsu: Chapter 5 vs 10-14.
Posted On:11/03/2005 8:10pm
Thanks all. To you guys who say its almost impossible to work the heart: so if your heart rate is at 100+ for days and weeks and even years, that the heart isn't going to over work? That it will hypertrophy? (Well, of course you guys must be right, since its proven medically that the heart grows due to high blood pressure; but just for more thoughts. ^_^)
Yes, definetely helpful. Confirmation about enlargement of the heart, the muscles in the heart get too bulky, the walls of the chambers thicken, thus making the chambers themselves smaller. With the chambers smaller, the stroke volume decreases. Correct me if I am wrong.
Going further, are you saying, that under normal circumstances, the heart isn't supposed to enlarge at all?
If so, how is the heart supposed to work more efficiently, become stronger, increase stroke volume, and all these other benefits; without getting 'bigger'? Is it possible to increase the size of the chambers, where the blood flows into, thus increasing the size of the heart; but keeping the muscles not too bulky?
(From what I've heard, some endurance athletes have enlarged hearts too. If I recall correctly, Lance Armstrong's heart is 33% larger than normal)
Posted On:11/04/2005 9:54am
I have to check with my doctor buddy, but I think heart size is pretty much determined by genetics. Lance's success my be in part due to the genetic advantage of a large heart. You can always increase the strength of the heart muscle and its endurance, as well as increase your VO2 max for better athletic performance.
Posted On:11/08/2005 10:51am
Originally Posted by Scrapper
Exercise-induced cardiac hypertrophy is generally associated with steroid abuse or truly epic suplementation schedules, along with a supremely intense workout schedule.
Sorry, Scrap, but this is misleading - while cardiac hypertrophy can be associated with resistance training, and steroid abuse, hypertrophy is more generally associated with endurance training.
It's a basic adaptation to the increased circulatory demands of endurance athletes.
For a good general review, see
When this same individual adds a steroid or supplement that increases the growth of any muscle, it increases the growth of the heart as well.
I'm not sure this is supported by research - do steroids, by themselves, increase muscle mass, or do they promote the adaptations of muscle in response to exercise?
Power athletes, who also take steroids, show signs of cardiac hypertrophy; but, at least according to one study, steroids themselves only account for about 1/4 -1/3 the effects.
Certainly anabolic steroids are not good for the heart, but the problems are more complicated than just size.
If the heart gets excessively bulky, it loses flexibility, and the increased mass of the heart muscle decreases the size of the ventricles, which limits how much blood the heart can move.
I'm not sure how true this is; in skeletal muscles, you can increase bulk without losing flexibility, if you work flexibility along with size. And remember, the heart muscle is always being stretched.
You can also increase cardiac mass without necessarily decreasing the volume of ventricles.
Eventually, the damn thing is so muscular that it can produce incredible pressure, but no flow due to decreased ventricular capacity. Which produces tachycardia under stress. It is virtually impossible to accomplish this without chemical help; but not unheard of.
Maybe true in certain pathologies, but in general, I doubt it.
There is a relationship between stroke volumn and heart rate - to maintain constant cardiac output, if one is decreased the other necessarily increases. But can a normal heart muscle truly get so big as to drastically decrease stroke volume? I'm inclined to disagree. And even in the cases of steroid abuse, this explanation is a bit simplistic.
As for the original question, there is a relationship between hypertension and hypertrophy.
Hypertension can be due to an increase in peripheral resistance - in other words, it's harder to move blood through arterioles (this is typically the most resistant part of the circuit). In response, the heart must generate more pressure to maintain a constant cardiac output - a constant blood flow.
In response, the heart will typically become stronger; this may include hypertrophy.
However, it's a bit more complicated than that - hormones like epinephrine can change both peripheral resistance (vasocontriction or vasodilation), cardiac contractility and cardiac rate. If these hormones are constiutively high, then the heart and tissues lose the ability to respond to these hormones. But I'm going to ignore hormonal effects - it may be unncessarily complicated for this post - but I will say that exercise causes a transient increase in these hormones, while stress (and the associated hypertension) causes a long-term increase - and the body adapts differently to these two conditions.
With respect to hypertension, it's important to note that exercise itself induces a transient hypertension - when you exercise, blood becomes pushed out of muscles. Changes in cardiac output and vasodialation help counteract this, but, simply put, a contracting muscle is hard to move blood through.
So, regular exercise induces cardiac hypertrophy, by a mechanism similar to chronic hypertension. However, the hypertension of exercise is transient - your body adapts to a high pressure state, but can then return to a low pressure (which, in trained athletes, can be very low).
In the cases of hypertension, that high pressure is always there - which can lead to a mal-adaptive cardiac hypertrophy.
There are a few other factors of heart muscle that, at least for me, for now, are a bit too detailed to get into (seriously - it's a couple-three lectures worth of materal in an undergrad physiology course; we use one three-hour lab to cover this material, as well).
If you're interested, you might try googling "Frank-Starling law of the heart" or the role of cardiac muscle cell refractory period in fibrillation.
Posted On:11/08/2005 11:16am
My info came from a Ph.D (clinical Pharmacist) buddy of mine during a conversation about suplementation and steroids. He seemed fairly convinced, and I took his word for it. I will concede that he may have been speaking in broad generalizations, and specifically citing worst-case scenarios, as opposed to generating actual reports, though.
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