Women who wear the wrong kind of bra could be damaging their breasts, researchers have warned.
The breast biomechanics team at the University of Portsmouth said poor support could lead to fragile ligaments in the breast being stretched.
They said that during exercise, breasts move up to 21cm (8.26inches), up and down, in and out and side to side - but most bras just limit vertical movement.
The researchers also warned that crop-top sports bras did not give enough support.
The research team has tested about 50 bra designs on hundreds of women during the past three years.
Wendy Hedger, one of the scientists who carried out the work, said that many women have strong preferences for certain styles of bra and won't buy anything else.
She added that habit also affects the bras women choose for everyday wear, with the wrong choices potentially causing breast pain or discomfort.
Ms Hedger noted that there's a social stigma about certain sizes. Many women don't want to be seen as too small or too big and buy a bra that doesn't fit well in order to be what they consider to be a normal size.