Move to some hill, watch your stamina when moving uphill, and downhill - while moving downhill stamina will leak with same speed as when moving uphill.

BTW i would change this to be super realistic and polished to 100%. Moving from A to B point is very time consuming, as a "forest man" i often go to forest TO HILLS etc, with about 25 KG carry. I dont have so big dificulties as soldiers in arma with 17 KG carry moving under smaller slopes (!). I think stamina should be easier to recharge and i have got idea. Stamina should be recharge by adrenaline, so when we are supressed, stamina should charge very qicly, as soldier is scared then, and wants to survive. Logic, isnt it? This is how human body work. Wanna example? You can easly meet boar in forest, when he start rush in yor way, what are you doing? Moving on the tree, even if in normal condition you were not able to do this. Now imagine situation when bullets are flying above you head. Please consider this option.