well...if you are doing a realistic impression and carrying a combat load then you will get in shape........
I have worn my Suunto a number of times and have seen sustained 140ish HRs.
Never did a calorie calculation but time in training zone was effective.
So when you guys trying to get in shape using airsoft are making gear choices then lightweight plastic is out....and real steel is in! LOL
Semper Primus: Always First