Maximizing calorie burn during cardio

I do cardio classes at my gym a couple days a week like spin, a kick boxing type class or step. The classes generally run around 55 mins and my HRM always indicates around 560-580 calories burned. Whether I am taking it easy, or really pushing hard, I never seem to be able to increase that number (since losing weight).

The problem is not with you but with the measurement. The heart rate monitor is guessing at the calories you burn in that hour by the number of time your heart beats, which is only minimally associates with the number of calories you burn.

If you have the same average heart rate for an hour, your heart rate monitor will report back more or less the same number, no matter how many calories you actually burned.

So I'm wondering, is there a maximum calorie burn you should aim for when doing cardio?

There is, but it's a lot higher than you think.

The most calories you can burn is dependent on a number of things. Your VO2max (the maximum amount of oxygen your body can deliver to the muscles and process per minute) is one. Your functional threshold (also called lactate threshold, onset of blood lactate, and anaerobic threshold) is another.

The highest VO2max ever recorded was about 7 liters per minute. Each liter is roughly 5 calories. So a world record holding athlete can burn 35 calories per minute for 5 minutes (then he will collapse and need to recover). An average, moderately trained female will do about 3 liters per minute. That's a maximum 15 calories per minute for 5 minutes before you need a break. Most heart monitors tell you far more than that.

To put times on them, the VO2max is roughly the hardest you can go for five minutes. The functional threshold is the hardest you can go for an hour. (I know, I'm oversimplifying, but I'm also not trying to write a treatise on aerobic energy delivery). Athletes spend their entire career trying to raise their VO2max and to sustain a higher percentage of it at functional threshold.

The "hardest" measurements that I mentioned are not measured in heart rate. If you keep working harder, you will never see a heart rate of 280 beats per minute. Instead, your heart becomes more efficient, pumping more blood per beat and putting more oxygen into the blood. The intensity must be measured in something more absolute, like power (wattage) or speed (under controlled conditions). Usually they are tested on a treadmill or a bike with the speed being gradually increased every minute until you cannot go any faster.

Burning more calories means going harder on an absolute scale (like speed or power), not a relative one (like heart rate), for the entire hour. Unfortunately, as you get fitter, your heart rate monitor cannot tell the difference. When you get fitter, you go faster at the same heart rate (whether you get leaner or not).

You win for the most helpful response, thank you!

So basically, I'll never know on my own? K cool thx.

You win for the most helpful response, thank you!

So basically, I'll never know on my own? K cool thx.

I do cardio classes at my gym a couple days a week like spin, a kick boxing type class or step. The classes generally run around 55 mins and my HRM always indicates around 560-580 calories burned. Whether I am taking it easy, or really pushing hard, I never seem to be able to increase that number (since losing weight).

The problem is not with you but with the measurement. The heart rate monitor is guessing at the calories you burn in that hour by the number of time your heart beats, which is only minimally associates with the number of calories you burn.

If you have the same average heart rate for an hour, your heart rate monitor will report back more or less the same number, no matter how many calories you actually burned.

So I'm wondering, is there a maximum calorie burn you should aim for when doing cardio?

There is, but it's a lot higher than you think.

The most calories you can burn is dependent on a number of things. Your VO2max (the maximum amount of oxygen your body can deliver to the muscles and process per minute) is one. Your functional threshold (also called lactate threshold, onset of blood lactate, and anaerobic threshold) is another.

The highest VO2max ever recorded was about 7 liters per minute. Each liter is roughly 5 calories. So a world record holding athlete can burn 35 calories per minute for 5 minutes (then he will collapse and need to recover). An average, moderately trained female will do about 3 liters per minute. That's a maximum 15 calories per minute for 5 minutes before you need a break. Most heart monitors tell you far more than that.

To put times on them, the VO2max is roughly the hardest you can go for five minutes. The functional threshold is the hardest you can go for an hour. (I know, I'm oversimplifying, but I'm also not trying to write a treatise on aerobic energy delivery). Athletes spend their entire career trying to raise their VO2max and to sustain a higher percentage of it at functional threshold.

The "hardest" measurements that I mentioned are not measured in heart rate. If you keep working harder, you will never see a heart rate of 280 beats per minute. Instead, your heart becomes more efficient, pumping more blood per beat and putting more oxygen into the blood. The intensity must be measured in something more absolute, like power (wattage) or speed (under controlled conditions). Usually they are tested on a treadmill or a bike with the speed being gradually increased every minute until you cannot go any faster.

Burning more calories means going harder on an absolute scale (like speed or power), not a relative one (like heart rate), for the entire hour. Unfortunately, as you get fitter, your heart rate monitor cannot tell the difference. When you get fitter, you go faster at the same heart rate (whether you get leaner or not).

You win for the most helpful response, thank you!

So basically, I'll never know on my own? K cool thx.

You will know through trial and error over the long term what your target calories per minute should be. If you try to burn more calories per minute and then your body is too sore/tired/weak the next day to go in, then that's above your max calories per minute you should target if you are going to exercise for the same amount of time since over two days you are actually burning half as many calories per minute.

Too weak to work out? Sorry, I don't know what that means.