Query about trampoline exercise!
 

OK, I have a huge trampoline in my garden (I think 14 feet) and I spent about 15mins on it earlier with my sister (she's 12 and energetic so she's like my trampoline coach haha)

I didn't really break much of a sweat or puff and pant too much but I REALLY felt it in my butt and legs.
However, yesterday I spent 10mins on it and I felt it less and got more breathless.
Do you think the exercise was effective? Even if I get sore muscles should I carry on until I'm tired next time?

Oh, also, just how effective is trampolining as exercise?