Having knackered my foot a bit recently and had to cut down running I've started swimming again to make up some of the exercise I'm losing out on. I've been looking at calorie calculators (via Google) to try to work out how much less energy I'm using than when I was running properly, but having tried 3 and come back with scores of 225, 445 and 627 calories (for 40 mins or 1000m swimming depending on what they asked), I'm not really any better off.
I'm not very good at swimming and can only do breaststroke, which wasn't an option on the ones that had a choice of strokes, and am about 105kg in case that helps.
Anyone know of a decent calorie calculator for swimming, or even a way of working it out that might make some sense? I would be very grateful