Hayflick Limit

Cells in the human body can only proliferate (divide) a certain number of times in a lifetime. This is called the Hayflick Limit. Every time your cells divide they lose a bit of DNA. Eventually, as you age you start losing useful bits of DNA. Human cells can divide about 50ish times before they hit the Hayflick Limit.

Being hard on your body basically boils down to killing off your cells and forcing them to divide to replace themselves, accelerating their aging. For example, if you are a boxer and take a lot of punches to your kidneys, you’ll force your kidneys to repair the damage via cellular division, and those are a finite resource. When people start breaking down of old age what basically happens is the number of cells that can continue to go through healthy divisions starts becoming scarce, so organs have a hard time maintaining themselves.