I'm getting older (27 now... DAMN) and I have noticed that things aren't as erm.. firm as they used to be. I've been skipping on and off for a while, but yesterday I hit it... hard.
Skipping really is a lot harder work that I thought it was. I had to stop like 7 times to catch my breath. Today, my thighs, calves, stomach and my arms are really sore. It's a nice pain. It's a "I've worked out" pain. I like it.