According to a study conducted by  Dr. Mark Tarnopolsky, a professor of pediatrics at McMaster University in Hamilton, Ontario, regular exercising will keep you young. The research was published in The Proceedings of the National Academy of Sciences, exercise reduced or eliminated almost every detrimental effect of aging in mice.  The study was performed on mice who were genetically engineered to age rapidly (due to a defective mitochondrial polymerase gamma (PolG), which disables the repair of mitochondria). Mitochondria are parts of a cell which convert energy into forms (by combining nutrients and oxygen) that are usable by the cell. They are known as the powerhouses of a cell.  However, through its regular functioning mitochondria can develop unstable chemicals that harm the cell itself, which, according to recent scientific discoveries, plays a major role in aging. Mitochondrial dysfunction and oxidative stress are considered to be major contributors to aging and aging-associated cellular death. Improper diets or insufficient nutrient absorption can also have an impact on healthy mitochondrial function. 

In the study performed by Dr. Tarnopolsky genetically altered mice were separated into 2 groups: one that exercised regularly and another did not. At 3 months of age (20 years of age in humans), the active group was required to run on a wheel for 45 minutes 3 times a week.  By 8 months (60 in humans) the inactive mice aged drastically, became gray and lifeless.  All were dead before reaching one year.  The exercising group, however, still had their dark fur, brain volume, muscle mass, and where  still moving around in their cages. They still had functioning mitochondria.

The researchers were suprised by the outcome of the study.  As Adeel Safdar, senior PhD student working with Tarnopolsky said, “I believe we have very compelling evidence that clearly show that endurance exercise is a lifestyle approach that improves whole body mitochondrial function, which is critical for reducing morbidity and mortality. Exercise truly is the Fountain of Youth.”  Dr Tarnopolsky  acknowledged that “exercise is the most potent anti-aging therapy available today or likely forever.”
Therefore, mitochondrial decline and muscle weakness that develop with age can be reversed with exercising. Exercising can decrease your chances of developing diseases and has a positive effect on the aging process itself.