Forgot what it feels like to work out

So, I've been reading that if you stay active it helps you have a quicker and easier labor. I've been going on walks regularly but yesterday at 36w5d, I decided to step it up a notch and try some stairs. I went to the nearby dam where I've worked out a lot in the past. I walked up and down the stairs 3 times before I was completely spent. This morning my calves completely KILL! I guess I forgot that going up a giant set of stairs 3 times is still a workout!! Lets just add that to my growing list of aches and pains lol!