Research showed that after each workout, regardless of cup size, your breast tissue stretches, and this sagging is irreversible," says Lofton. So short of duct-taping your boobs down, if you want to exercise and keep them perky, make sure your sports bra is supersnug. 

Experts claim that wearing the wrong size or type of bra for exercise can lead to neck and back pain, breast pain and irreparable damage to the ligaments inside the breast which can result in breasts drooping and stretch marks. 

He said: 'If you wear the wrong regular bra, you're probably going to be wearing the wrong sports bra... 

'Sports bras because there's more activity and motion, the breast is held together by fatty tissue and Cooper's ligaments, with all the stress of movement, it does stretch out, it doesn't go back. 

'It can cause the breasts to sag and cause injury to the connective tissue of breast and cause pain.' 

He said women with bigger breasts who wear ill-fitting bras could also experience neck issues, back pain or nerve entrapment. 

He said breasts should not move during exercise, adding: 'The basic rule of thumb as far as I'm concerned is that your breasts should be closer to your chin than your belly button'.

Once the Cooper's ligaments are damaged, he said they reach 'a point of no return' that leads to stretch marks and breasts dropping.