Upper body pain – huh?

Today after my run (training has begun for my 2nd marathon), I started to feel pain in my upper body. This doesn’t happen after a run so I started thinking, what could cause this? Then I remembered I started playing my Nintendo Wii 2 days ago. While I haven’t played with it much, the swinging action is doing a number on me. I thought I was in decent shape, but it’s making me work in a way I didn’t expect. Thanks Nintendo!