I am the anomaly of being a petite but very large-breasted woman (34G - try finding a bra that supports that!) and I always have a hard time finding a suitable bra to run and play basketball & soccer in. Bra manufacturers are stupid and think that large women need large bras and small women always use small bras. There are a lot of bad sport bras out there. Eventually I'll have a breast reduction but until I do I need to keep a good supply of supportive bras. Anyway, this web site (posted below) may be of interest to some - men included!!! ;-) It is an animation of women's breasts at various sizes and what happens to them with no bra, a regualar bra, and a bra known as the "Shock Absorber." It looks like they only sell these things in the UK. If anybody knows of a retailer in the States, please post here.
Bounce-O-Meter (NSFW):
http://www.shockabsorber.co.uk/bounceometer/shock.html
Web site: