Les Mills Body Pump

I usually use the weight lifting/strength training option under exercises which for 50 minutes gives you 161 calories however think this is a bit light on especially if you are lifting a decent squat and leg weights. I looked on another website and it came up with like 500 calories which i think was a bit high..... (500 cals is the equivilent of a 7km run for me and i know that i dont exert as much energy in pump as a 7km run which i do quite often) I think the only way to get a real answer is to use a heart rate monitor, however if you are really having a go and lifting some good weight i would think around 250 calories would be in the ball park.
I have always wondered the same thing about spin classes however there is such varying levels of effort in every participant again i think a heart rate monitor is the only way to go.....
Hmmm i think i just talked myself into a buying a heart rate monitor......