FACT. There are no muscles in the breast. FACT. Female breasts are primarily composed of glandular tissue and fat and are held in positionby delicate ligaments. FACT. Any excessive amount of breast movement, as happens during exercise, puts strain on these ligaments and can cause them to stretch. In the long term this means that breasts sag. FICTION. Your ordinary, everyday bra is good enough to use when exercising. FACT. Tests have shown that breast movement is reduced by 38% when wearing an ordinary bra but this rises to as much as56% with a Shock Absorber sports bra.