What specifically happens to both the bones and muscles?

Bones

* Bone density decreases. This is due to a decrease in the production of osteoblasts, the cells that build new bone.

* Bones become more porous. This is due to a decrease in the production of collagen, the protein that gives bone its strength.

* Bones are more likely to fracture. This is due to a decrease in bone density and strength.

Muscles

* Muscle mass decreases. This is due to a decrease in the production of myocytes, the cells that make up muscle.

* Muscles become weaker. This is due to a decrease in muscle mass.

* Muscles are more likely to atrophy. This is due to a decrease in muscle use.

These changes in bones and muscles can lead to a number of problems, including:

* Increased risk of falls. This is due to decreased bone density and muscle strength.

* Muscle pain and stiffness. This is due to decreased muscle mass and flexibility.

* Reduced mobility. This is due to decreased muscle strength and flexibility.

* Increased risk of fractures. This is due to decreased bone density and strength.