Sarcopenia

Sarcopenia is the natural loss of muscle mass that happens as you get older. Muscles and bones work as a team — your muscles pull on your bones every time you move, and that pulling force is part of what signals bone cells to stay active. When you lose muscle, your skeleton gets less of that stimulus, which is linked to lower bone density. People with sarcopenia tend to have noticeably lower bone density than people who keep their muscle mass up.

The connection goes beyond mechanics. Working muscles release chemical messengers called myokines, including one called irisin, which encourages bone-building cells to get to work. Bone sends signals back too, through a hormone called osteocalcin, which helps muscles use energy. Another molecule, myostatin, can hold back both muscle and bone activity. Because muscle loss and bone loss show up together so consistently, researchers now think of sarcopenia and osteoporosis as closely linked parts of the same aging process rather than two separate problems.

Protecting your muscle is one practical way to support your bones as you age. That said, strength training mainly works on the muscle side of this relationship and rarely builds much new bone on its own — the two tissues respond differently to exercise, even though they're in constant conversation with each other.