A bra with sensors built into the fabric could help scientists make exercise a more comfortable experience for women.
Australian researchers believe their creation will help bra makers make their future designs a better fit.
Exercising wearing a poorly-fitting bra can raise the risk of long-term injury.
The findings, in the Journal of Biomechanics, may allow more accurate laboratory analysis of breast movement during exercise.
Current methods of testing bras in the lab rely on rigid sensors which can, they say, affect the way that the fabric moves during tests.
So far the fabric has been tested on two women, with size 36D and 38DD bra sizes, and recorded 6.9cm (2.7inches) of movement as the "larger" woman jogged on a treadmill.
The University of Wollongong researchers said that currently some large-breasted women could not take part in exercise because it was simply too painful.
They wrote: "Our results show that the fabric sensors are suitable to monitor breast motion and brassiere function.
"Brassiere designers will have the ability directly to assess the effects of changes to each brassiere component."
Breast pain is a major problem during exercise - a recent study by Dr Joanna Scurr at Portsmouth University found that between 45% and 60% of women suffered it during exercise, with a slow jog just as painful as a fast sprint for some.
Some estimates have suggested that up to 70% of women in the UK are actually wearing the wrong sized bra every day, increasing the chances of shoulder and back pain.
Dr Scurr said: "This is an important area because so many women in the UK suffer from breast pain - and often don't bother to report it.
"Any research which could improve bra design would be very welcome."
She added: "Women need to make sure they are fitted for a bra, and don't keep the same bra for too long - I've spoken to some women who keep the same bra for 10 years.
"My research suggests that, when it comes to sports bras, the traditional 'encapsulated' design, where each breast is held separately in a cup which encloses it completely, works better than some of the more modern designs which work by pressing the breasts into the chest to stop movement."