Not burning as many calories

napilibay

Hi
I'm on week five of my cardio dvds. When I started, I was burning almost 500 calories in 40 minutes according to my polar heart monitor watch. However now I'm averaging 400...does this mean I'm getting in better shape and my body isn't working as hard?

Equus5374

As your fitness level improves, your heart rate does not need to go as high to compensate for the work you're doing. If the only thing being measured to determine caloric burn is your heart rate, then yes, as it drops, your calorie burn will be lower. If you're not eating back exercise calories, it shouldn't matter.

lorib642

nm, but congrats on getting healthier

rankinsect

It means your heart health is improving and now your heart rate doesn't go as high.

That doesn't actually mean you burn less calories, just that using heart rate as a means of estimating calorie expenditure tends to overestimate calorie burns for the very unfit and underestimate calorie burns for the very fit, because the better your cardiovascular fitness, the less your heart rate increases for the same actual calories burned.

It's not your body becoming more efficient in terms of calorie expenditure, but your heart becoming stronger and ejecting more blood per beat. If you're at "average" fitness, HRMs tend to be decent estimates of calories burned, but the more you deviate from the average in either direction, the more they under or overestimate.

It would be far more accurate to compare cardiac output (total amount of blood moved per minute) to calories burned, but measuring the second half of that equation (stroke volume, the amount of blood ejected per heartbeat) requires an ultrasound of the beating heart, something consumer electronics can't do. Maybe someday we'll have wearable echocardiogram units actually measuring our cardiac output in real time, but not today.

rankinsect

Oh, there is one thing though that does decrease calories burned by exercise - weight loss. It makes sense - when you're moving a larger and heavier body around, it takes more energy than to move a leaner, lighter one.

napilibay

rankinsect wrote: »

It means your heart health is improving and now your heart rate doesn't go as high.

That doesn't actually mean you burn less calories, just that using heart rate as a means of estimating calorie expenditure tends to overestimate calorie burns for the very unfit and underestimate calorie burns for the very fit, because the better your cardiovascular fitness, the less your heart rate increases for the same actual calories burned.

It's not your body becoming more efficient in terms of calorie expenditure, but your heart becoming stronger and ejecting more blood per beat. If you're at "average" fitness, HRMs tend to be decent estimates of calories burned, but the more you deviate from the average in either direction, the more they under or overestimate.

It would be far more accurate to compare cardiac output (total amount of blood moved per minute) to calories burned, but measuring the second half of that equation (stroke volume, the amount of blood ejected per heartbeat) requires an ultrasound of the beating heart, something consumer electronics can't do. Maybe someday we'll have wearable echocardiogram units actually measuring our cardiac output in real time, but not today.

Thank you! I have lost five pounds and doing cardio 5x/week so that makes sense.