Why not only use your heart to excercise?

Not really cycling related but I have been thinking about this question for a while. All forms of cardiovascular exercises require you to use some muscle groups in addition to your heart.
What will happen if your heart rate is increased artificially without exercising? is that even possible and will you still burn calories?

I think I saw it answers somewhere before. In essence, muscle fibers need to contract and relax to use energy. Heart rate is the function of this process to facilitate transport of chemicals in and out of cells.

Sure it’s possible, plenty of legal and not pharmaceuticals can do it for you. You would burn slightly more calories because your heart is doing more work, but it would be like the extra calories you burn by taking stimulants.

You burn calories exercising by doing work. Whether that’s pushing the pedals or walking or any kind of movement. That takes oxygen and fuel to burn for energy. Your heart rate goes up to deliver more of that to the muscles that are performing the work, but it’s not really the main work done.

So no, not really. The extra calories would be on the order of what you’d burn sitting on the couch lightly squeezing a tennis ball versus actually working out.

The heart is a muscle and a fairly small one, so, increasing only heart rate just increases the calories burned from the heart doing more work. Your conclusion is a case of correlation not causation: When your other muscles work hard, they require more blood delivered to them. It’s this work that the muscles do that requests your heart rate to increase.

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Guess you’ve never been stressed in any way, shape, or form?

Oh, it’s possible! I have several HRM spikes into 90% HRmax zone when cruising along in Z1/2 and nearly getting run over by a car. Also not a good thing, all those unused fight/flight chems swishing around in your body causing havoc. Stay calm, bro. :v:

Also…you don’t want a giant heart.

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Sure it is possible. A sauna would be a classic way. The heart rate increases even though you are sitting down, because the heart starts working as a heat pump to circulate blood to the surface of the skin (where the heat can escape through the evaporation of sweat), rather than an oxygen pump.

Your question itself mentions the cardioVASCULAR system (OK, my emphasis), which is really the heart and lungs working together. It is oxygen consumption that is the marker of calories being burned, not your heart rate.

and what is the maximum heart rate you could reach in a sauna? Is is even possible to go close to your threshold HR?

Last month my daughter had a severe illness and her heart rate was in the low 130s for much of 48 hour period despite being fully sedated. She also was borderline hypoxic. If you ignored the ventilator and just looked at HR and pulse ox, it looked like she was on a marathon ride at altitude camp.

She’s fine now but she certainly did not experience a fitness boost from the effort :wink:

Legs might be useful too.

Okay first major thing to think about is HR is just a response to stress. It can be increased by emotional stress, which will not make you fitter; it can also be increased by physical stress, which can make you fitter. The major difference between these is that there are responses by tissues that you use in exercise and these tissues will want to repair and build themselves up against future stress.

With exercise, the muscles are the cells doing the physical work. This creates metabolic stress, which increases signals for the muscle cells to adapt so that future metabolic stress can be managed. This is how we get fit (by repeatedly doing so). There are other kinds of stress that come into play during exercise and cause other changes (think stress on the heart muscle, blood flow, thermoregulation, etc.). These all cause similar build-it-back-stronger responses.

When we go through emotional stress, we are ‘preparing’ our bodies for the ‘fight-or-flight’ response, so our heart rates get raised by adrenaline (this would help us be more able to run or fight should the need arise). If you sit there and are stressed, you are not using your muscles, so they will not get the same signals as they would during exercise - in fact, the signals they receive are to the effect of “we’re going through a lot of stress and we aren’t using the muscle, so let’s save our resources and not work on you”.

TLDR: The tissues that you use tend to respond the most. By using muscle, we tell the muscles to become stronger and more efficient.

Because I like riding my bike. :slightly_smiling_face:

Venous return depends in large part on peripheral muscle contraction. simply increase heartrate, ventricular filling will suffer without sufficient return. Cardiac output would top out pretty quickly, and the positive adaptations would be limited.

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In a sauna of 176 F, after 20 min, my pulse gets all the way up to 72.

Makes more sense now. Thanks!

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