Muscle mass with age

Doomed to lose muscle with age?  These images show what a 40y.o. athlete's leg looks like.  But 'HEALTH' is fitness over age.  Can we maintain muscle mass over age like we had in our 'youthful' 40s? 

You tell me::

A new study called, "Chronic Exercise Preserves Lean Muscle Mass in Masters Athletes," which you can read HERE graphically illustrates what happens to your muscles (with and without) the type of regular and beneficial exercise that the sport of triathlon provides.
The image above is a cross section of a 40-year-old triathletes legs and the associated muscle. But the two images below are the really interesting and telling ones.

40-year-old Triathlete

At 74-years old...these are your legs on triathlon & these are your legs without triathlon

74-year-old Sedentary Man

74-year-old Triathlete

As you can tell, the 74-year-old masters triathletes legs are not unlike that of the 40-year-old triathletes legs. The study's authors go on to write:

"It is commonly believed that with aging comes an inevitable decline from vitality to frailty. This includes feeling weak and often the loss of independence. These declines may have more to do with lifestyle choices, including sedentary living and poor nutrition, than the absolute potential of musculoskeletal aging.
In this study, we sought to eliminate the confounding variables of sedentary living and muscle disuse, and answer the question of what really happens to our muscles as we age if we are chronically active. This study and those discussed here show that we are capable of preserving both muscle mass and strength with lifelong physical activity."

They conclude by writing:

"The loss of lean muscle mass and the resulting subjective and objective weakness experienced with sedentary aging imposes significant but modifiable personal, societal, and economic burdens. As sports medicine clinicians, we must encourage people to become or remain active at all ages. This study, and those reviewed here, document the possibility to maintain muscle mass and strength across the ages via simple lifestyle changes."