In case you haven’t heard of Cooper’s ligaments

The main ligaments that support the breasts are the Cooper's ligaments, which are bands of fibrous connective tissue that anchor the skin to the underlying chest muscles and provide structural support and shape. The breast is also supported by the skin itself and the underlying pectoralis fascia (the membrane covering the chest muscles).

Cooper's Ligaments

Structure:
These ligaments are a network of thin, fibrous bands within the breast tissue.

Function:
They help maintain the breast's shape, provide structural integrity, and connect the breast's outer layer (skin) to the muscles underneath.

Effect of Damage:
Over time, or with excessive movement, these ligaments can stretch or become damaged, leading to breast sagging.

Other Supporting Elements

Skin:
The skin covering the breast plays a crucial role in its support and overall shape.

Pectoralis Fascia:
Cooper's ligaments originate on the pectoralis major and minor muscles' fascias (the connective tissue coverings) and disperse throughout the breast, providing an anchor point.

Why Support Matters

Stability:
Adequate support helps to limit excessive breast movement during activities like walking and running.

Comfort:
This movement can put tension on the internal supporting structures, leading to pain.

Prevention of Sagging:
While some sagging is inevitable with age, using a well-fitting sports bra helps to support the Cooper's ligaments and reduce movement, which can slow down the process of stretching and sagging.