dear doctors

[Guest murad_math]

dear friends and brothers of science

can you tell me how many hours in every day the human heart takes rest

i mean how many hours does it work and how man it relaxes

[blike]

It works all the time. Sometimes it works harder, sometimes it works less. It all depends on the person and their lifestyle. If you're an active person, your average heart rate is likely to be higher.

[spacemanspiff]

i thought that if you were in good cardio shape your resting heart rate would be lower.

[Skye]

I'm not even remotely close to a doctor, so I may be wrong here.

 

Cardiac cycle for a 0.8 second heart beat: Atria contract for 0.1 s then ventricals contract for 0.3 s (this makes up the systole, where the heart expells blood) then the heart relaxes for 0.4 s (this makes up the diastole, where the heart takes in blood).

 

If you just consider the systole and diastole the heart is relaxed for half the cardiac cycle. But the atria are only really contracting for an 1/8th of the cycle and the ventricals for 3/8ths.

 

If you are healthier then you should have a lower resting heart rate, your heart needs to pump less often to keep you going. Regular exercise keeps you healthier overall, and I've read that anaerobic exercise can make you heart muscles more flexible which should give it a higher capacity thus lower resting heart rate. Unless you are working really hard, like running all day, then your lower resting heart from regular exercise should oversome the period of higher heart rate during the exercise.

[blike]

Originally posted by spacemanspiff

i thought that if you were in good cardio shape your resting heart rate would be lower.

 

Right, but since you're active your heart-rate is raised higher more often [when you're running, etc] than those who are inactive. my bad, i wasn't very clear on that.

[Glider]

Originally posted by Skye

I'm not even remotely close to a doctor,

Good for you! Nasty things they are....with pointy eyes and beady teeth....and they smell funny.

...so I may be wrong here.

You ain't, which demonstrates nicely the importance of a doctorate when it comes to being right.

[Radical Edward]

Originally posted by blike

Right, but since you're active your heart-rate is raised higher more often [when you're running, etc] than those who are inactive. my bad, i wasn't very clear on that.

 

yeap... then you get those interesting cases such as some cyclists who have to be very careful after they have been cycling to have a proper warm-down period, since their resting heart rate is so low. My Biology teacher had a heart with unusually large capacity, and he was very healthy too.

[Skye]

Interesting, it seems strange that it would make it harder to recover if you have a low resting heart rate.

 

I was training for a kickboxing fight about a year ago (didn't happen, accursed promotors:mad: ) and I had great recovery, I could get my heart rate well over 200, then be able to talk fine after half a minute. Usually to say I am not *%#$ing doing that again.

[Ahmad]

Originally posted by Skye

If you are healthier then you should have a lower resting heart rate, your heart needs to pump less often to keep you going. Regular exercise keeps you healthier overall, and I've read that anaerobic exercise can make you heart muscles more flexible which should give it a higher capacity thus lower resting heart rate. Unless you are working really hard, like running all day, then your lower resting heart from regular exercise should oversome the period of higher heart rate during the exercise.

 

Just to add to that, the heart of a trained athlete does have a lower heart rate, but that doesn't mean that it is not doing the same amount of work. It will be beating less frequently, but each beat will be stronger. Each beat will use a higher amount of energy than that used in the beat of an untrained person. This is because it needs to pump more amount of blood per beat.

 

The amount of work a person has to do is better correlated with the amount of blood he is pumping per unite time, or the cardiac output, which is basicly the same for trained and untrained individuals in the resting state.

[Ahmad]

Originally posted by Radical Edward

 

yeap... then you get those interesting cases such as some cyclists who have to be very careful after they have been cycling to have a proper warm-down period, since their resting heart rate is so low. My Biology teacher had a heart with unusually large capacity, and he was very healthy too.

 

I'm not sure how related is that to the heart rate, but the warm-down period is very important in this case for the pressure change.

 

In this case, an individual is doing a dynamic exercise in which his muscles are contracting. These muscles have blood vessels going through them, and when they contract, they help in moving the blood towards the heart. They also cause a rise in mean arterial perssure. In this context, these muscles are called "booster pumps".

 

When these muscles are working very hard, their componenet in the mean arterial pressure will be very high. If they stop working suddenly, their large contribution to the current mean arterial pressure will go away, and there will be a large pressure drop because of that.

 

This is why you should stop your muscle action gradually, to allow the regulatory mechanisms to follow up until you reach resting state.

[Sayonara]

Originally posted by Glider

pointy eyes and beady teeth

You must be on the NHS.

[Radical Edward]

Originally posted by Ahmad

When these muscles are working very hard, their componenet in the mean arterial pressure will be very high. If they stop working suddenly, their large contribution to the current mean arterial pressure will go away, and there will be a large pressure drop because of that.

 

This is why you should stop your muscle action gradually, to allow the regulatory mechanisms to follow up until you reach resting state.

 

is that part of the reason for dizziness or light headedness sometimes if you have been exercising really hard then relax suddenly?

[Ahmad]

Originally posted by Radical Edward

 

is that part of the reason for dizziness or light headedness sometimes if you have been exercising really hard then relax suddenly?

 

That's as fas as I know, yes.

 

Note that this only applies to what is called dynamic exercise, in which the muscles keep contracting forcefully and periodically. It doesn't apply to static exercise, like weight lifting. So it depends on what you are talking about.