The myth of aging = deterioration

'Advanced age is not a static, irreversible biological condition of unwavering decreptitude.

Rather, it is a dynamic state that, in most people, can be changed for the better, no matter how many years they have lived or neglected their body in the past - yes, you do have a second chance to right the wrongs you have committed against your body. 

Your body can be rejuvenated. You can regain vigor, vitality, muscular strength, and aerobic endurance you thought were gone forever. This is possible, whether you are middle aged or pushing 80.

The 'markers' of biological aging can be more than altered: in the case of specific physiological functions, they can actually be reversed.'

Footnote: yoga is uniquely placed to guard against the aging process, due its  effective but low-impact focus on all-over joint, muscle and bone health.

The above main quote is extracted from: William Evans, Biomarkers - The 10 Keys to Prolonging vitality

Also see The New Yoga for People Over 50 by Suza Francina for a wonderful introduction on keeping mind and body healthy and creak-free.