WHEN the University of Wollongong academic Julie Steele first published a scholarly review on the science of breast biomechanics, which found that breast bounce caused 50 per cent of women pain during exercise and daily life, postcards flooded in from around the world.
''It was the first time in my 30 years working on injury prevention that I've received handwritten postcards,'' Professor Steele said. ''Women from all over the world, from all walks of life, wrote to me, often with stories about their discomfort, thanking me for taking this topic seriously.''
Realising that she had tapped a need, Professor Steele submitted a paper to an academic conference in the male-dominated field of biomechanics. Organisers rejected it, assuming she couldn't be serious.
In 2005, when Professor Steele was invited to present an international keynote address on her research, the organisers asked her to remove the term ''breast'' from her title. She did so, replacing breast with ''bra''. Her first slide, though, was defiant: ''Breasts, what's the problem?''
The problem is that regardless of bra size, age or health, many women suffer breast pain or discomfort during everyday life and exercise because their breasts are not properly supported, said Professor Steele, who has written 13 papers on the topic.
Most women assume supportive sports bras will be uncomfortable. ''But they don't have to be,'' said Professor Steele, who runs Breast Research Australia (BRA), one of only two independent research institutes of its kind in the world.
Researchers in Britain estimate that during sport, the average breast can move 21 centimetres (about the length of a box of tissues) in a figure eight movement. Breasts don't only move up and down, they move side to side, and even in and out. Given the average breast weighs about the same as 1.2 litres of milk and is held in place by skin and Cooper's ligaments, that's a lot of bounce or slide.
Dr Joanna Scurr from the University of Portsmouth Breast Health Research says the big question is why we know so little about the movement of breasts.
''Sports has always been dominated by men and for them studying breasts is seen as slightly laughable. For women, though, it's completely credible.''
When she tells people she studies ''bouncing breasts'', instead of breast biomechanics, people laugh nervously but always want to know more.
Professor Steele, who is the associate dean of research at the faculty of health and behavioural sciences of Wollongong University, said there were ''significant medical implications of inappropriate breast support''. Poorly adjusted bra straps can cause headache, backache, and numbness and tingling in the hands because the straps apply excessive pressure to nerves that cross the shoulder and innervate the hand.
Many women stopped physical activity because of it and it put some young women off exercise for life. ''Young girls, they frequently become embarrassed as their breasts develop,'' said Professor Steele.
Exercising in Pyrmont, Michelle Levingstone of Manly Vale said once she decided to buy a proper sports bra, she eliminated any discomfort. Her exercise partner, Mandy Egger of Double Bay, who went to the gym regularly, said she saw a lot of young girls who were uncomfortable and wore baggy tops to hide their breasts.
Sue Bull, of Hornsby, was clear as to why women continue to face this problem: ''If men have problems with their bits, they fix them. That's why they invented Viagra. But if women have problems with their bits, people don't care.''
For help in choosing the right sports bra go to sma.org.au