I'm a physio in women's health - and, yep, some sports are just not good for your pelvic floor.
From memory - something like 78% of elite trampolinists have stress incontinence. Gymnastics, running and athletics are also fairly grim. 25% of women aged 15-35 wet themselves during sport.
The problem is that the bounce generates a lot of intra-abdominal pressure, and if your muscles are too weak - you'll leak.
It's a scourge - a third of women aged 35-55 wet themselves. A third!
The good news is that 85% of simple stress incontinence can be cured by doing pelvic floor exercises and 5 sessions with a physio.
If you look at my profile you'll find a link to my (amateurish) website - I'm trying not to fall foul of advertising - there's a page about the exercises on there.
I use twitter as a training tool - @gussiegrips "I tweet, you twitch your twinkle"
I'm trying to get this into the mainstream, speaking with our governing body and trying to get mumsnet to run continence as a campaign. Meanwhile, I'm about to do a Fringe run with a comedy show about continence (erm, seemed like a good idea at the time) - imaginatively entitled, Gusset Grippers. I'm hoping ot get some publicity, it's public health stuff disguised as scatological humour...
Now, to answer your immediate problem...there is some new evidence from the States saying that women participating in impact sports should use internal support.
Many runners use tampons to wodge everything up there and keep themselves leak-free.
www.incostress.com is a silicone version of that, it's got good evidence behind it and it does work. I don't represent the company, it costs about £30 and is resusable.
There is another gadget, contrelle activeguard which desmit systems sell, think they are about £50 for 30.
The best thing you can do is get an assessment. Ask your GP for a referral to a women's health physio, or find one privately. Don't put up with it - most cases can be cured, you've just got to do the exercises.
Oh, found the research - 80% of trampolinists. I'm rather impressed by my memory! trampolining paper
contrelle doodah
incostress