In addition to keeping your breasts from bouncing around and improving their shape and appearance, a well-fitting bra can be helpful in other ways, including preventing injuries to breast tissue and improving your posture. Find out if your boobs are big enough. Take off your shirt or bra and jump around a little, How much do your boobs bounce? The best way to preserve your breasts is to match your sports bra type to the activity. 'Movement of the breast varies from sport to sport,' says Professor Scurr. 'In games such as tennis, the upper body rotates so the breasts move a lot from side to side.