It's amazing how hard it is to walk up stairs lol. I did one stairwell (P4 up to 24) which took 10 minutes, tookthe elevator back to P4 then did the other side (P4 - 24) which took 15 mins. I took each step deliberately and launched my weight up from my heel almost like a hop each step. My quads and stomach are burning like crazy. I thought my legs were in pretty good shape i guess not. Heart rate probably shot up to 150-160ish and i broke a sweat