I agree with wressler, army PT is mental stress more than anything. Eventually your mind just blocks out the pain/dulls it to the point where you think about other things. Since my drill sergeants didn’t want us lifting weights, at night I would put my kevlar body armor on, put my feet up on a bunk, and proceed to do pushups. When I could do many reps of that, I wore my dufflebag with my battle buddy’s kevlar. By the end of basic I was about 180lbs big and ripped up. Everyone else looked like christian bale from the machinist days.
I would say the reason not many soldiers get to t-man muscle status is because they aren’t educated on how to workout properly. They think like that one poster; that normal pushups will increase your maximal strength with increased repetitions. Not to mention everyone telling me how situps were making their abs visible. I just smiled and agreed. Maybe it’s because I was with fellow grunts, but that’s the general concensus of working out for them.
When you think about it logically though, there aren’t many people who lift weights to build muscle, and fewer still that understand all the principles for getting to that point. So it shouldn’t really shock you that a small percentage of soldiers have large muscles. They are normal people too (despite what marines tell you).