Motion studies have revealed that when a woman runs, more than 50% of the breasts total movement is vertical, 22% is side-to-side, and 27% is in-and-out. A 2007 study found that encapsulation-type sports bras, in which each cup is separately molded, are more effective than compression-type bras, which press the breasts close to the body, at reducing total breast motion during exercise. Encapsulation bras reduce motion in two of the three planes, while compression bras reduce motion in only one plane. Previously, it was commonly believed that a woman with small to medium-size breasts benefited most from a compression-type sports bra, and women with larger breasts need an encapsulation-type sports bra. Mechanism
Anatomically, a females breasts do not contain any muscle but are composed of soft, glandular tissue. Breasts are composed of mammary glands, milk ducts, adipose tissue (fat tissue) and Coopers ligaments. Mammary glands remain relatively constant throughout life. Fat tissue surrounds the mammary glands, and its volume will normally vary throughout life. Although the exact mechanisms that determine breast shape and size are largely unknown, the amount and distribution of fat tissue and, to a lesser extent, mammary tissue, cause variations in breast size, shape and volume. Some experts believe Coopers ligaments, which are connective tissue with the breast, provide some support within breasts, but theres no agreement on whether they provide support or simply divide breast tissue into compartments. Treatment
Bras
Since breasts are an external organ and do not contain muscle, exercise cannot improve their shape.
The study results were presented at a conference of the American Society of Plastic Surgeons.According to Rinkers research, there are several key factors. A history of cigarette smoking "breaks down a protein in the skin called elastin, which gives youthful skin its elastic appearance and supports the breast." The number of pregnancies was strongly correlated with ptosis, with the effects increasing with each pregnancy. As most women age, breasts naturally yield to gravity and tend to sag and fold over the inframammary crease, the lower attachment point to the chest wall. This is more true for larger-breasted women. The fourth reason was significant weight gain or loss (greater than 50 pounds (23 kg)). Other significant factors were higher body mass index and larger bra cup size.In Rinkers study, 55% of respondents reported an adverse change in breast shape after pregnancy. Many women mistakenly attribute the changes and their sagging breasts to breastfeeding, and as a result some are reluctant to nurse their infants. Research shows that breastfeeding is not the factor that many thought it was. Rinker concluded that "Expectant mothers should be reassured that breastfeeding does not appear to have an adverse effect upon breast appearance." Also discounted as causes affecting ptosis are weight gain during pregnancy and lack of participation in regular upper body exercise. Effect of vigorous exercise
When running, breasts may move three-dimensionally: vertically, horizontally and laterally, in an overall figure-8 motion. Unrestrained movement of large breasts may contribute to sagging over time.