Why is it?

polyesterchesters

I work out every day on my elliptical. I do use a heart rate moniter. It seems the longer (number of days) I use the machine, the less calories I burn while using it. Two weeks ago, I was on for 75 minutes and burned 680 calories (according to my HRM), today, the same amount of time burned only 535. Why the big difference?

cmriverside

Your body adapts very quickly to exercise that is repeated. That is why you hear it said so many times here that you need to "change it up" in other words, do different stuff.

Walk, weights, bike, rowing, stairmaster, swimming.

cmriverside

Plus you are now more fit cardiovascularly, so you need to step it up intensity-wise.

epoeraven

Another factor - the more weight you lose the less you have to move to exercise so you burn less calories.

imagymrat

You don't have to switch cardio machines, stay on the elliptical if that's what you like, but do a minute or two at a much higher intensity, then bring it down to a"rest" pace, then hike it up again, you'll be shocking your body, the calories will go back up and now you've added some interval training.

cmriverside

Good point imagymrat! I sooooo hate the elliptical I'd use any excuse to get off it!

Questfor250

I noticed that yesterday and today on the treadmill. I was over 100 calories less on my bodybugg than what the treadmill said. In the past the bodybugg gave me more burn than the treadmill said. Now thanks to these posts I understand why and will make adjustments. Thank you.

Azdak

I work out every day on my elliptical. I do use a heart rate moniter. It seems the longer (number of days) I use the machine, the less calories I burn while using it. Two weeks ago, I was on for 75 minutes and burned 680 calories (according to my HRM), today, the same amount of time burned only 535. Why the big difference?

The HRM is not an infallible device--it doesn't even count calories. It *estimates* calories burned based on your heart rate response to steady-state aerobic activity, but EQUALLY IMPORTANT, based on the setup of the device.

If you HR response to a submaximal workload is less than what it used to be, it's not a sign that you are burning fewer calories, it is a sign that YOUR AEROBIC FITNESS LEVEL HAS IMPROVED, so that it is not as high a percentage of your maximum as it used to be.

Unless you have lost weight, you are still burning the same number of calories that you were burning before--but you haven't told your HRM that your aerobic capacity has improved, so it is assuming that you are working at a lower intensity.

This is one of the key problems with using HRMs to estimate calories. All too often, people get the whole process *kitten*-backwards and start to assume that your aerobic intensity/calories burned is based on your heart rate, when in fact the truth is just the opposite.

The first thing you need to do is change the VO2 max setting on your HRM.

If you are doing the elliptical every day, then the other suggestions about changing intensities, adding interval workouts, etc, are all good ones. It is necessary to vary your training stimulus in order to make continued progress. But it has nothing to do with the lowered calorie numbers on your HRM.

Wolfena

Yup - everyone said it all....

You're fitter, lighter, muscles are getting used to that particular exercise.

Sucks, but the less we weigh and the more in shape we are, the harder it is to burn calories!!!

cmriverside

Excellent, azdak, that's the first time I've ever heard that! My HRM, though I love it, I don't really believe it anymore. But that was based on a gut feeling, not actually knowing why. Thank you!