"Decreased muscle strength is associated with difficulty in performing functional activities such as stooping, crouching, or kneeling (SCK) in older adults."
That is a quote from a recent study that spoke of the dangers of losing strength as you age. The research went on to say that as you lose muscular strength your chance of injury can also increases. This means you may be more susceptible to falls or hurting yourself doing everyday activities with every passing year.
I know from firsthand experience that it took a full year to help one of my clients over the age of 60 to fully heal her lower back injury which happened after suffering a hard fall one winter. The good news is that she is now injury free and stronger than ever since taking up a 3 day a week exercise program. Her stability, posture, strength, and energy have all increased and I believe that anyone, no matter the age, can benefit from a structured strength training program.
Source: January issue of Physical Therapy, the scientific journal of the American Physical Therapy Association