There are a lot of factors which can cause sagging breasts, but there are also some ways to prevent breasts from sagging too early.
Women have always been preoccupied with how their breasts look because breasts are an important part of the body that expresses femininity and beauty, and there is nothing beautiful about sagging breasts.
There are a lot of factors that influence the breasts and causes them to sag like, age, size, breast feeding and gravity. In order to prevent the breasts from sagging you can do several things:
Massage your breasts once in a while with moisturizing cream to help them maintain it's elasticity and good posture. Exfoliate and keep the skin healthy.
Tone your pectoral muscles by doing exercises that are meant for this particular area. Exercise using dumbbells because they will tone your breasts and arms, and do chest press exercises. You don't have to over do it, you don't want to build muscle mass, you just want to tone so don't push yourself too hard.
Keep a good posture of your body. Don't arch your back by
keeping your shoulders forward because your breast will look like
they are sagging even if they aren't.
Keep your back and shoulders straight to make them look more firm.
Watch your weight because as you gain weight your breasts become larger and if you gain weight too quickly your skin could stretch beyond it's stretching capacity causing stretch marks. Also gaining and losing weight regularly could cause sagging breasts because the skin could lose it's elasticity due to constant stretching and shrinking.
Drink a lot of water, approximately 8 glasses of water a day to keep your skin and body hydrated. Water is as important for your organism as well as for your skin because it will maintain skins elasticity.
Wear a bra when you are running so they won't bounce and stretch the skin to much. It will give you the support you need and allow you to be more comfortable while you exercise as well.
Remember to take proper care of your skin and your breasts to prevent them from sagging and keep them in their best shape for as long as you can.