Not sure about the ADF or other Emergency services, but the CFA recruits need to be physically fit & are conducted through "beep" tests prior to being accepted for training.
Once you are in though, that's it, you can go to pasture all you want and believe me, they do!!!
Now, I'm no oil painting, but would it/could it be feasible to include a minimum fitness level for these types or organisations?
(Bit od a drift there...sorry)