heart rate and calories burned

I use www.braydenwm.com/calburn.htm

I love my heart rate monitor too. Every time I work out, I put the exact amount of calories I burned on this site, I like it to be exact.

Check out Amazon.com, this one is only $50 with free shipping. You only need a basic one like this

http://www.amazon.com/Polar-Heart-Rate-Monitor-Watch/dp/B000ASDGU8/ref=sr_1_1?ie=UTF8&s=hpc&qid=1254331467&sr=8-1

I have this one though, and LOVE it

http://www.amazon.com/Polar-Transmitter-Monitor-Exercise-Fitness/dp/B000X8WA5C/ref=sr_1_12?ie=UTF8&s=sporting-goods&qid=1254331467&sr=8-12

Reaching back into the depths of my memories, I seem to recall that the heart becomes more efficient at pumping blood when one exercises a lot. This would mean it has to work LESS, not more, to get the same amount of blood out to the rest of the body. Consequently, the resting heart rate is lower, because it doesn't have to work so hard.

Reaching back into the depths of my memories, I seem to recall that the heart becomes more efficient at pumping blood when one exercises a lot. This would mean it has to work LESS, not more, to get the same amount of blood out to the rest of the body. Consequently, the resting heart rate is lower, because it doesn't have to work so hard.

so does that mean that fit people with strong hearts burn fewer calories during the day (going against the notion that exercise boosts your metabolism ) or that each pump of the heart for fit people equates to more calories than for a less fit person, meaning that even a heart rate monitor will give inaccurate results for the very fit or the very unfit, because a fit person's heart will beat few times (having a lower heart rate) than an unfit person's.

It seems to me that something doesn't add up here.

What doesn't add up is that the popularity of HRMs has evolved into a misconception that there is somehow a direct relationship between heart rate and metabolism.

Metabolism is defined as the chemical reactions that occur in living organisms to sustain life. In human beings, this process is powered primarily by processes used to generate ATP. In order to generate this energy, we need fuel and oxygen. A calorie is actually a unit of heat measure. The processes of generating ATP also produce a consistent amount of heat energy. A calorie (specifically a "gram calorie") is the amount of heat needed to raise the temperature of 1 gram of water 1 degree Celsius. What we refer to as "calories" are actually "Kilocalories", the amount of heat need to raise 1 Kg of water 1 degree C (technically, the term should have a capital C--we should all be writing "Calories" instead of "calories").

Direct measurement of calories "burned" is cumbersome and impractical. The most common way of estimating caloric expenditure in humans is to measure oxygen uptake. It is oxygen uptake that is the most "direct" form of measuring metabolism and calorie expenditure.

Under certain conditions, there is a relationship between heart rate and oxygen uptake. During aerobic exercise, cardiac output (the volume of blood pumped by the heart) must increase in order to deliver more oxygen to the tissues to keep up with the increased demand. Some of the increase in cardiac output occurs from an increase stroke volume--the amount of blood pumped by each heart beat. Stroke volume maximizes at a relatively low intensity and any further increases in cardiac output occur though an increased heart rate only (heart rate also increases at lower levels of exertion as well, but it is not the sole component of increased cardiac output).

So, again, with normal dynamic aerobic exercise, an increase in heart rate reflects an increase in oxygen uptake. To oversimplify, what a Polar HRM does is senses that an exercise heart rate is "X%" of a person's HRmax, so that translates into "Y%" of maximal oxygen uptake (VO2max) and knowing the VO2 allows the calculation of calories expended.

There are several factors that must be known before these calculations can be made: HR rest, HR max, and VO2 max. The first one is easily measured--the second two are usually estimated.

As I said, this is oversimplified, because to determine these calculations has required much more sophisticated research on the part of Polar and other manufacturers, but that is essentially what is going on.

There are a number of conditions during which HR can increase without any increase in oxygen uptake. These include: emotional stress, thermal stress, illness, pressure-mediated increases in HR that do not result in increased cardiac output, and cardiovascular drift. Under these conditions, the change in HR is NOT related to changes in cardiac output or VO2, and therefore HR cannot be used to estimate caloric expenditure.

Under resting conditions, HR is not a reflection of overall metabolism. The decrease in heart rate that one sees in more fit individuals reflects an increase in stroke volume, not a decrease in metabolism.

So, in summary, heart rate is not a direct indicator of caloric expenditure. At best, it is an indirect measurement, and even then only under certain specific conditions. Because HRMs by major manufacturers (Polar, Suunto) have become pretty sophisticated and good at measuring calories expended during aerobic exercise, and HRMs provide convenient access to this data, it is understandable that many average exercisers would assume that HRMs are directly measuring calories, but this is not the case.