Jump jump...

I recently bought a Jumperoo Colton and he loves it!  When we first got the jumper Colton wasn't sure what to do with it, but as soon as he learned how to jump he hasn't stopped...he literally will jump for like 30 minutes.  It is great exercise for his legs and helps strengthen his back, but my goodness I'm not sure how his legs aren't sore! Mine would be sore after just 2 minutes of jumping like he does.