Relative to the large, backyard kind of trampoline, you might want to read the 
following cautionary article:
http://abcnews.go.com/Health/Wellness/report-warns-trampoline-dangers/story?id=17292265

Del

From: Sara Mandal-Joy 
Sent: Tuesday, September 25, 2012 9:00 PM
To: silver-list@eskimo.com 
Subject: Re: CS>rebounding.

If you do a search you'll find a ton of information, many articles, on both the 
benefits of rebounding, AND the dangers of rebounding on a mini tramp.  On a 
mini trampoline is a "great" way to damage your feet, ankles, and knees.  DON'T 
DO IT!!!  But there is no better excercise than rebounding on a good 
"rebounder" - the kind that usually cost at least 300 bucks and have the right 
kind of springs and material.  I'm not sure how the giant backyard ones measure 
in this equation - have no experience with them and haven't researched them.  
Probably, almost certainly, better than the cheap minitramps.  But I'm sure 
there is a range of quality with them as well, some better absorbing and 
cushioning the stress of the landing than others.  Sara

  Marshall,
  Some time ago someone on this list gave information on a doctor who advises 
rebounding but NOT with a mini trampoline.  Do you or someone else have his 
name or the article?
  Thanks Mary