For some reason, a soldier, a FULLY TRAINED SOLDIER, wearing just his underwear (or shorts and a t-shirt) and carrying nothing but a pistol, seems to get short of breath, blurry vision. and a loud pounding sound in his ears, after
Sprinting for 20 yards. (ok. 30)
CrouchRunning (one stance down) for 40 yards.
Crouchwalking practially ANY distance uphill.