[katieHaylor (OP)]

Chris asks:

Why do we get slower and weaker, less agile and generally less physically able as we age? I have trained heavily all my life (competitive running, swimming, cycling but also yoga and weights), yet  in spite of these efforts I get slower and weaker. Physiologically, what happens to the body that causes this degradation?

What do you think?

[evan_au]

Aging (or senescence) also occurs at the cellular level, when cells cease dividing.
- This is an important mechanism for blocking the uncontrolled growth of cancers

When you are young, lifting weights causes the muscle cells to break; the stem cells divide and the muscle grows.
- When you are old, many cells no longer replicate, so if you kill some muscle cells, they are not replaced as effectively.
- This suggests a transition from active body building when young to maintaining the muscle mass that you have in a healthy state when older
- Keeping up a healthy level of exercise is important; a healthy heart and healthy circulatory system preserves brain function: "What's good for the heart is good for the head!".

See: https://en.wikipedia.org/wiki/Cellular_senescence

[alancalverd]

The older we get, the better we were.  Ask any rock musician.