I never heard of Kettlercise before so looked at some videos. Kettlercise doesn't look very demanding. Less heavy breathing than my 12 minute/mile pace jogs. There are very impressive claims about how much calories Kettlercise can burn, like 657 calories in 45 minutes (24yo F, 5'6", of unknown weight)
I tried using the calories burnt as function of HR formula* on this page:

Is it possible to measure calorie burn from heart rate alone?

That formula comes up with numbers I think are credible for my calorie burn when I am jogging (*I have a pretty good estimate of my real VO2MAX).

But the HR that would be required for a 24yo female to get to 657 cal/53 minutes, requires all kinds of extreme values in the formula above. VO2max = 50, 70 kg, avg HR = 195. Do those numbers make sense(??) Is the formula that inaccurate?

Or would I be right to think that Kettlercise energy expenditure is probably being over-hyped?

I never heard of Kettlercise before so looked at some videos. Kettlercise doesn't look very demanding. Less heavy breathing than my 12 minute/mile pace jogs. There are very impressive claims about how much calories Kettlercise can burn, like 657 calories in 45 minutes (24yo F, 5'6", of unknown weight)
I tried using the calories burnt as function of HR formula* on this page:

Is it possible to measure calorie burn from heart rate alone?

That formula comes up with numbers I think are credible for my calorie burn when I am jogging (*I have a pretty good estimate of my real VO2MAX).

But the HR that would be required for a 24yo female to get to 657 cal/53 minutes, requires all kinds of extreme values in the formula above. VO2max = 50, 70 kg, avg HR = 195. Do those numbers make sense(??) Is the formula that inaccurate?

Or would I be right to think that Kettlercise energy expenditure is probably being over-hyped?