There is really not one clear answer from either the scientific or medical community about when and why the aging process begins.
It is well accepted by the scientific community that muscle damage and atrophy begins around age 40 and the atrophy will continue at a rate of 1% per year if we do not strength train on a regular basis. What this means in simple terms is that if you do not strength train you run the risk of losing up to 1% of your muscle mass per year, but you do not have to settle for that bleak future.
You don’t have to go far to see the effects of muscle damage and atrophy since only about 30% or less of our adult population “admits” exercising weekly on a regular basis. (Exercise is broadly defined as exerting your muscles to keep physically fit which can be a variety of forms of activities). In public, you can observe an adult’s posture and their overall body shape to get an idea of which person exercises regularly and who are the “couch potatoes” or worse yet, the ones that sit all day (and night) staring at a computer.
Building muscular strength is the most important form of exercise for everyone at most every age. Actually, strength training should be the foundation of fitness and if practiced on a regular schedule it will allow you to compete or participate in your favorite activities for a long time while reducing the potential for injuries. Why you may ask? Because if you strength train with proper techniques you will be stronger and will be able to play longer.
For example, in just a few weeks after strength training with custom designed workouts people in their sixties, seventies, and eighties (that have not strength trained for years) will show noticeable and measurable improvement in their:
Muscle tone and size
Fat to lean muscle ratio
Overall physical appearance
What we don’t see and cannot measure in the gym is the improvement some will get on the inside of their bodies (which medical tests at their primary physician will be able to prove). So, it is important that before starting any new exercise or diet program you should always get clearance from your primary physician or specialist. Then after a few months into your strength training program specific medical tests will show if you have improved (for example) in your cardiovascular ability or your bone density.