I think its very important.
If you're BO you will have to carry a load and potentially walk a looong way.
If you're bugging in then you may need to protect what you've got or if out sussing whats going on you may need to out run the scum!
Also, there will be more heavy and sustained work than what we're used to.
I started running again at the beginning of last year and by sept was running 10k. But illness and injury has meant I haven't run for 3 months although I walk daily up a steep hill fast!
What has worried me is how unfit my children are. Both are skinny jims and eat well but my daughter is walking a mile with me each day and shes out of breath and complaining her knees hurt. Shes 11 yrs!!!!!!

I blame the schools for their namby pamby sports curriculum..............
So GET FIT whichever way you can. DVD's at home, walking, running etc, most can be done for free.