Heart Rate Monitors- How accurate are the calories burned?

I got a heart rate monitor watch w/ chest strap, and it is telling me I only burn 400-ish calories in an hour of intense kickboxing. It just doesn't seem accurate to me. An hour of medium intensity on an elliptical machine, when I program in my weight/sex/age, it tells me that I burn closer to 800-1000 range. What's up with this? I am 5'6", 125#, female, 25 yo. How many calories should I be burning in an hour of intense cardio class??

most likely your HRM is a much better estimate than the elliptical. Next time you do the elliptical wear your HRM and program the machine, and you will see the HRM is much lower.

As long as your HRM is programmed correctly to your stats, I'd go with that. Machines are inaccurate as I learned after getting my HRM - machines seem to overshoot.

This is from another source that is highly accurate.

Kick Boxing
Kick boxing is a high-impact cardio activity that engages all of your core muscle groups. Kick boxing movements may include roundhouse kicking, punching, twists and other fast-paced movements that build strength and endurance, and it can burn hundreds of calories per hour. This is typically a solo or partner activity, and it's a great way to get and stay in shape!

This activity burns approximately 658 calories per hour

I got a heart rate monitor watch w/ chest strap, and it is telling me I only burn 400-ish calories in an hour of intense kickboxing. It just doesn't seem accurate to me. An hour of medium intensity on an elliptical machine, when I program in my weight/sex/age, it tells me that I burn closer to 800-1000 range. What's up with this? I am 5'6", 125#, female, 25 yo. How many calories should I be burning in an hour of intense cardio class??

The better your fitness level, the less calories you will burn.

just Clarifying that the MACHINES are off and not the HRM

most likely your HRM is a much better estimate than the elliptical. Next time you do the elliptical wear your HRM and program the machine, and you will see the HRM is much lower.

The cardio machines get your heart rate from your hands. This is not as accurate as the reading from the chest strap HRM as far as calories burned. I used to work with Polar, that is how I got this information.

I'm still laughing at the "approximately 658 calories per hour"....

The HRM Is definately More accurate than the Machines. the machines don't take into account your fitness level. they base it on the average person, which in todays society isn't very fit.

Fitness level has little or no effect on the calories burned at any comparable intensity level.

If a 60 yr old who weighs 150 lbs and an Olympic runner who weighs 150lb run at 6 mph, they will both burn roughly the same number of calories. It will feel much easier to one than the other, but it's the "absolute" intensity that determines calorie burn, not the "relative" intensity.

If you have properly setup your HR Zones on your HR Monitor then it should be much more accurate than the machine. Like it's already been stated, the machine does not account for Genetics, Fitness Level, etc.

Heart rate "zones" do not play any role in how many calories you burn--other than the fact that working harder burns more calories.

Genetics--at least not for the average person-- and fitness level don't really factor in either.

most likely your HRM is a much better estimate than the elliptical. Next time you do the elliptical wear your HRM and program the machine, and you will see the HRM is much lower.

The cardio machines get your heart rate from your hands. This is not as accurate as the reading from the chest strap HRM as far as calories burned. I used to work with Polar, that is how I got this information.

Hand sensor readings can be affected by quality of contact -- things like perspiration, hand cream, etc, can affect the signal.
With an unaffected signal, handrail sensors are just as accurate as chest straps--both signals are transmitted to the console display by the same Polar receiver module plugged into the console.

In any case, machines do not rely on heart rate to estimate calories burned. That's because they measure the actual workload that is being performed. The reason why so many machines (not all) inaccurately estimate calories is that they are lazy and sloppy about the equations they use to translate the measured workload into an aerobic intensity. It's no different than what cheap HRM manufacturers do. Some manufacturers -- Life Fitness for example -- put a lot of research and effort into developing machine-specific algorithms and thus their calorie estimates tend to be the most accurate in the business--often more accurate than an HRM.

I have a Garmin 310XT. I use it to time intervals, gauge pace and measure distance. I don't use it for any activity that doesn't have a steady state aerobic component to it like lifting, yoga or sitting on my couch watching television. Even then, for the steady state stuff the calorie burn is an interesting number to kind of see but I just always end up going with the ACSM metabolic calcs when logging. At my weight (115 lbs) and my typical training pace (6 mph) it rounds down to 500 calories an hour (~10 METs). It's an easy to remember number and if I go a little faster or a little slower the difference isn't huge so I just go with that and call it a day.

If you have properly setup your HR Zones on your HR Monitor then it should be much more accurate than the machine. Like it's already been stated, the machine does not account for Genetics, Fitness Level, etc.

Heart rate "zones" do not play any role in how many calories you burn--other than the fact that working harder burns more calories.

Genetics--at least not for the average person-- and fitness level don't really factor in either.

HR Zones absolutely play a role in how many calories you burn. My Max HR is roughly 185 which is about 8 BPM higher than what most machines would have posted on them. For me to workout at 75% of my max to burn roughly 14 calories per minute I need to maintain a HR above 139BPM. At 50% of my Max and burning roughly half the number of calories per minute my average HR needs to be around 93BPM for the duration of the workout.

If I used the charts on most machines my max HR is 175 which means 88BPM to maintain 50% or 131 for 75%.

Google is your friend here...

ETA: To get to my point. If your HR zones are setup wrong because you did not properly calculate your Max HR then you will not be able to accuratly calculate your caloric burn per minute based on average HR. Genetics role in this is that not everyone's Max HR can be calculated based on 220-Age. Some people, for whatever reason, just have a higher or lower max than others and it has everything to do with genetics.

The HRM Is definately More accurate than the Machines. the machines don't take into account your fitness level. they base it on the average person, which in todays society isn't very fit.

Fitness level has little or no effect on the calories burned at any comparable intensity level.

If a 60 yr old who weighs 150 lbs and an Olympic runner who weighs 150lb run at 6 mph, they will both burn roughly the same number of calories. It will feel much easier to one than the other, but it's the "absolute" intensity that determines calorie burn, not the "relative" intensity.

Not true, your level of fitness will determine your level of effort. In your example a fit olympic runner could likely run at an easy pace 6MPH for an hour at less that 50% of his Maximum HR. While a 60 year old that is out of shape performing the same exercise might exceed 80-90% of his/her Maximum HR.

Had you said that the two people in your example both worked for the same amount of time at the same level of physical effort which would mean that their average heart rate over that time was equal then you would be correct.

I am referring to absolute intensity, i.e. oxygen uptake, not relative intensity, which is percentage of maximum. Relative intensity means little when calculating rate of caloric expenditure (obviously it will affect total calories burned during a workout if one can maintain a lower intensity much longer than a very high intensity).

Caloric expenditure is based primarily on oxygen uptake and the oxygen demands for steady-state aerobic exercise are relatively constant--by that I mean that the energy cost for our example speed of 6.0 mph is roughly 10 METs. Doesn't make any difference who is doing it or their fitness level. 10 METs might be an easy effort for someone highly conditioned, with a VO2max of say 20 METS and a very difficult effort for someone with a VO2 Max of 12 METs, but the energy cost is still 10 METs. Heart rate does not make any difference in calories burned for an activity with a fixed energy cost. In the example we are using, the elite athlete might have a heart rate of 110, or 50% of HRR, the other person a heart rate of 140, or 85% of HRR. However, both are still working at 10 METs. Since the rate of calories burned is METs x body weight, if they weigh the same they will burn calories at roughly the same rate.

The ACSM metabolic equations, which are the accepted standard for this sort of thing, do not use height, age, gender, fitness level, or heart rate as factors.