Nearly one in five women say their breasts stop them participating in physical activity, according to new research.
Physical activity levels are not influenced by breast size, which suggests they could be a barrier to exercise for women across all bra sizes, the survey by the University of Portsmouth's Research Group in Breast Health found.
Researcher Emma Burnett surveyed women in Southampton, Portsmouth and Hampshire, and found that breasts were ranked fourth as a barrier to exercise after lack of energy, time constraints and health reasons. They were ranked above other barriers including cost of exercise, access to facilities, not having the right clothing, not having any company while exercising, and feeling embarrassed about doing sport.
The research - published online in the Journal Of Physical Activity And Health - found that 17% of the 239 women surveyed were discouraged from participating in physical activity because of their breasts.
The most influential factors preventing women taking exercise include not being able to find the right sports bra and being embarrassed by excessive breast movement.
Miss Burnett said: ''This latest research is crucial because it shows that breasts are an important factor to consider when investigating what deters women from exercising. One third of women in the study were not meeting physical activity guidelines, but improving breast health awareness may help to encourage participation for these women.
''We had plenty of anecdotal evidence to suggest that breasts are a barrier to exercise but this is the first study to provide evidence that they're affecting women's participation in sport.
''I expected the findings to show that breasts are a barrier but I was quite surprised at the percentage - it was higher than I thought.''
Miss Burnett said she hoped the research will help educate women about breast health awareness and encourage them to get active. She would also like manufacturers to take note that some women struggle to find the right sports bra.
The survey of women from Portsmouth, Southampton and the surrounding areas of Hampshire found that those who know more about breast health are more likely to participate in physical activity and more likely to wear a sports bra. Those with lower awareness were not as active.
She said: ''Women who aren't aware of the benefits of wearing a sports bra when exercising are those who exercise in the wrong kind of bra and then experience pain. This pain means they stop exercising, which is a shame because if they knew the difference a good sports bra can make, I'm confident they would have a more positive experience of taking part in physical activity.''
Professor Joanna Scurr, who leads the Research Group in Breast Health, said that if women do not wear the right sports bra, they risk damaging the fragile Cooper's ligaments which, once damaged, are irreparable.
Prof Scurr said: ''When the breasts are not supported appropriately and there is tension on the ligaments and skin of the breast, it can result in strain and over time this may lead to a stretching of the breasts' natural support, which could lead to permanent breast damage.'