As much as it can be a blessing to be generously endowed, an energetic workout can be painful. Read up on the science behind the bounce, and discover how to buy the best bra for the job.

Finding larger bras for vigorous activity is a tough proposition. And yet, the right bra can make the difference between a walker and a jogger, or a woman who sticks with her exercise regimen and one who gives up.

"Breast size and pain caused by exercise can be a real barrier to women doing exercise," believes Joanna Scurr MD, a sports scientist at the University of Portsmouth in the UK who pioneered the study of breast movement.

But as more and more women are seeking an active and healthy lifestyle, bra support is getting better, including some styles that are designed specifically for the well-endowed woman. If you've been wearing two bras at the same time for high impact activity, take a look at what we found out below.

Sports bra basics
Scurr's research shows that breasts actually move in three directions, not just the up-and-down bounce that is most visible. While a woman is walking on a treadmill, there is also breast movement from side to side and in and out. Additionally, the speed of breast movement during exercise can be a significant contributor to pain, which means the transition from walking to jogging is a signigicant moment, chest-wise.

Besides pain, there is the unfortunate issue of droop and sag. Excessive breast movement damages the naturally fragile support of breast tissue and can result in permanent damage to the figure. Young women especially have a chance at preventative maintenance if they get into a good sports bra early.

Bra design tackles the wiggle and jiggle in two ways. Compression bras press breasts against the chest to limit their movement. Encapsulation bras support each breast individually. Some bras are a combination of both styles.

According to Scurr's research, each breast moves independently, which points to greater effectiveness from encapsulation bras. Compression bras, she maintains, limit bounce, but not the movement in other directions.

Big brands
All sports bras are made from wicking fabrics that absorb sweat to keep you dry and cool. They need to stay put — no one wants to tug her bra in the middle of tennis serve. And they need smooth construction that does not irritate the skin by rubbing and chafing. Fortunately, many sportswear manufacturers have grown wise to the fact that women with larger chests like to work out hard, so shopping for them is a lot easier. One manufacturer is Moving Comfort, which offers five different styles of high-impact sports bras in larger sizes. Champion has many models that fit women of all sizes, but the Double Dry Action Shape Bra is praised by more than one WeightWatchers.com editor. As a bonus, Champion frequently has bra sales on its Web site (ChampionUSA.com).

Women with very large busts, however, still find it hard to find a bra that allows more than light movement. Don't give up; there are products out there, you just have to know where to look. In 1993, Enell founder Renelle Braaten, an avid volleyball player, cobbled together a bra with her seamstress mother that gave Renelle the support and comfort she hadn’t been able to find. Retailer Title Nine calls this bra the "Last Resort," which says it all. Its 10 sizes fit women from a 32-52 band size and DDD cup. The design combines encapsulation and compression with front closure and a full coverage back. It's not pretty, but it works.