that is damaged. by radiation for example. it's fixed by d.n.a. repair mechanisms. but as we get older there's an accumulation of damage caused by oxygen free radicals radiation or errors during my ptosis. our cells become less efficient. we suffer a loss of organ function. in the heart become weaker. lungs no longer work as well. liver and kidney function also start to decline our main organs that filter waste. so we start to show signs of where one thing leads to another decline in cardiac and lung function means our bodies aren't adequately supplied with blood and oxygen so they become weaker the downward spiral continues because we feel weaker we exercise less. it's a vicious circle. regular exercise is one way of delaying the aging process.