You might have seen a very fit and/or strong/bulky guy taking the elevator..
Now why would he do that when he looks like he could outrun it with stairs? He might have the time to do it, is he lazy? But then if he's lazy, how is he strong/bulky or fit? It might be DOMS (Delayed onset muscular soreness).
If you work out hard enough, you get micro tears in your muscles which your body then repairs. Delayed onset muscular soreness starts 1-2 days after a workout and can last for a week ( Yep! That truly is no pain no gain.) This delayed muscle soreness is great, it is by far my favourite. It is a great indicator that you've had an effective workout, you are constantly reminded that your hard work did not go to waste! Delayed onset muscular soreness is also a great reminder that you have to keep feeding your muscles nutrtion, afterall, nutrition is the key to the lock of a great body!
Do not forget to drink a lot of water, not underestimate sleeping properly, stop making common mistakes to become happier!