Exercise has very little if anything to do with tits going downwards. They are made of fat (for feeding of infants) not muscle. Exercising the pectoral muscles underneath them may help a teeny tiny
bit, but won't make much difference. Wearing a very supportive bra pretty much all the time may help a little also. Doing those "I must I must improve my bust" exercises are pretty fun though
Tits naturally go downwards due to time, pregnancy and breastfeeding, and fast weightloss.
The extent of the drooping is influenced by genetics, how many pregnancies and how big the person's breasts got whilst pregnant (dramatic increase then decrease causes 'deflation', a little yo-yo is unlikely to), and dramatic weightloss (same).
As Thom Yorke sang "Gravity always wins"
Google "007 breasts" for galleries of normal breasts. Not pornographic, but has loads of pics there. God knows how I came across that site lol! x