Breasts can move several inches during exercise
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.
And they warned crop-top sports bras did not give enough support.
Many women don't want to be seen as too small or too big
Wendy Hedger, University of Portsmouth
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: "Many women have strong preferences for certain styles of bra and won't buy anything else.
"They won't even look at anything that doesn't look like the sort of bra they are used to wearing.
"In sports bras, for example, many women won't buy a bra that resembles their everyday bra and does up at the back - they think if it can't be pulled over their heads like a crop top, then it's not a real sports bra.
"But this is not true and many sports bras do up at the back in the same way as a traditional bra and do a very good job of supporting women."
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 added: "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.
"And many other women are unaware that they are wearing a badly-fitting bra or unknowingly wear the wrong bra size because they are routinely being sold ill-fitting bras."Some women forget that their shape and size change and they might have to go through several changes in bra size over their lifetime, especially after breastfeeding and the menopause."