I have the same HRM you have - the F11. (I LOVE it, by the way!) 1600 calories burned sounds really really high. Like ridiculous high. But, then again, I've never done one of A-Jock's mish-moshes, the very reason being that I am pretty sure they'd give me a heart attack. LOL! So who knows, maybe you WERE working out hard enough to burn 1600 calories... but something tells me it just ain't right.
An hour of kickbox cardio for me may burn 300-350 calories according to my HRM. So, by that logic, I would expect to burn about 600 calories for 1 hr 45 min. Of course, we're 2 different people with 2 different max HRs and resting HRs, and all that fun stuff.
One thing that pops into my head right away is maybe you should have your max HR tested physically. The formula used by the F11 HRM is not bad (it uses the Karvonen Formula), but your max HR is determined primarily by genetics and it can vary significantly among people of the same age/weight/sex. A stress test can tell you what your max HR actually is, and then you can enter it into your HRM and get more accurate calorie counts. Your max HR may actually be quite a bit higher than the calculated number, which would account for the reall high calorie burns you're seeing on your HRM.
You may also want to do the Fitness Test several times and take an average of your numbers to get a more accurate reading. The Fitness Test gives you a number comparable to your VO2 max (sort of), but you need to do it when you're very relaxed, with no distractions. It would also be worth figuring out your resting heart rate and entering that into the HRM as well. Same goes for HRsit (average heart rate while sitting quietly). You can adjust all these numbers manually in the F11. When you do this, it has more accurate, personalized information to work with when calculating calorie burn.
Hopefully that made some sense - I never know how much people already know about heart rate training, so I don't want to write a big novel about it. But if you need clarification on any of it, let me know.
