Back in the Jurassic period I went to field medical school for the second time. There's an interesting story on why I went again. I was in my thirties. I was in good shape, looked good in uniform, went to the gym most every day, and coached youth sports. Due to the reason I went again, I wanted to blow it away and excel in all aspects of the course. I did a little cardio in my daily workouts but wanted to increase my run capabilities. One of my corpsmen was a SEAL HM2 on two years shore duty. Rick, I'll call him--actually his name IS Rick. SEAL's first names aren't classified as far as I know. Anyway, he took me out and ran with me. Thrashed me even. Gave me a few running tips.
The best tip of all was and I quote, "Chief, if you want to improve your run times then you have to run." Roger that, young frogman. And I did. I zipped through field medical school--which is multi-times harder than Navy boot camp--like a young fella. Push-ups, sit ups, rope climb, runs, and humps. Blew them away.
Physical conditioning is the easiest thing to prepare for in these type of events. If one is in shape, no, in really good physical condition, then concentrating on the other stuff is easier.