The Physics of Bras:
To best support breasts, a designer has to understand how they move. To that end, McGhee's team in Australia, headed by biomechanist Julie Steele, tags women with light-emitting diodes and asks them to run on treadmills. (The women run with and without bras, so the laboratory doors are bolted to prevent uninvited people from bursting in.) Computer systems then track the breasts' motions in three dimensions by following the moving lights. 'We can actually work out exactly where they're going, how they're moving, and how this movement is affected by bras,' Steele says. Breasts move in a sinusoidal pattern, Steele has found, and they move a lot. Small breasts can move more than three inches vertically during a jog, and large breasts sometimes leave their bras entirely. 'We have videos of women who, particularly if the cup is too low, spill all over the top,' Steele says.
I am in the wrong line of work.
Actually the article is quite interesting about the difficulties faced in designing bras and how important that is for women's health. Not enough pictures though. Sadly, it is entirely safe for work.