Anyone else pee when exercising?!!

This is a new discovery. I haven't done any home cardio exercise for a while. I still walk and cycle but decided to get back into doing the 30 day shred dvd. It's all good until I have to do jumping jacks! Oh dear. So now I have to wear a sanitary towel while I exercise. I'm 34 and have 2 children. My pelvic floor has always been pretty strong so I'm wondering...is this an age thing?