Until recently, muscle has been the stepchild of organs. Seen as an unsophisticated apparatus for locomotion and nothing more, it was undervalued. Research now documents the centrality of muscle function for a wide variety of processes essential to healthy aging.
A variety of social forces extradited muscle from respectable mainstream health. Muscularity once suggested physical labor and therefore a lower class station. More recently body builders hijacked the mesomorphic, minting steroid-fueled Rodin caricatures that were anything but a model of health.
Muscle also has been perceived as anti-intellectual. In the organ kingdom, it is the antithesis of the exalted brain, as in brain or brawn. It is our brain that distinguishes us from the great apes. Even within the muscle category one finds a hierarchy. Cardiac muscle appeared to carry none of skeletal muscle’s stigma. Academics might have jogged, meatheads pumped iron.
As we seem to learn over and over again, the body is not like a car. It cannot be taken apart and understood. Organs are orchestra members constantly signaling each other in order to create the symphony we call health.
Let’s take three of the most common health problems associated with aging; decreased insulin sensitivity and type 2 diabetes, weakened bones, fractures and osteoporosis, and forgetfulness, cognitive decline and dementia. One might not think muscle has anything to do with these conditions. You would be wrong.
Skeletal muscle is the primary tissue responsible for the disposal of glucose.
When the regulation of blood sugar levels fails, you head towards diabetes. Type 2 diabetes is associated with decreased cognitive capacity, brain atrophy, dementia and stroke. More recently, the link between these conditions and prediabetes has been made. There is now a growing body of evidence linking blood sugar levels in the high end of normal with significant brain pathology.
Blood sugar in this range appears to cause damage by triggering inflammation and excessive clotting. Brain regions responsible for working memory and verbal fluency are particularly sensitive to these changes.
Maintenance of muscle mass is essential to preventing the many problems caused by the loss of insulin sensitivity. Want to prevent diabetes? Think muscle.
The skeleton undergoes constant remodeling, even after we are fully grown. In fact, you replace most of your skeleton every ten years. When the dissolving of old bone outstrips the deposition of new bone, the skeleton becomes brittle and vulnerable to fracture. 34 million americans have osteopenia (low bone mass) and 10 million have osteoporosis (bone matrix mostly dissolved).
Many things contribute to this weakening of the skeleton including low calcium, vitamin D, estrogen in women and testosterone in men. But one of the most powerful culprits is a sedentary lifestyle. The stress placed on bone by weight-bearing activity promotes new bone deposition. This combination of gravity and muscle pulling on the bone tissue triggers healthy bone remodeling. This was first appreciated when young fit astronauts were exposed to extended periods of weightlessness in space. They returned with the bone and muscle loss of a senior citizen.
So how do you maintain muscle mass?
With typical aging, one loses muscle mass. I say typical to make clear that this occurs in most people but is avoidable. Our understanding of aging is largely based on how most people age rather than how one can age. Common conditions are not necessarily normal conditions.
Mechanistically, muscle atrophy is the result of an imbalance between muscle protein synthesis and muscle protein breakdown. Muscle work and protein consumption both act as powerful stimuli for muscle protein synthesis or anabolism.
Whether 9 or 90, the body maintains its ability to build new muscle throughout life. However, older muscle has a blunted response to anabolic stimuli. In addition, it is more vulnerable to compromised strength and function with even brief periods of reduced activity.
Research indicates that protein dose, leucine content and timing are important determinants of stimulating muscle protein synthesis. Also, optimal muscle work appears to be dependent upon exercise volume rather than absolute load lifted. This has important implications for the older individual embarking on an exercise routine.
Here are the techniques research has proven most productive for building and maintaining muscle mass as we age.
Dose: As you get older you need more protein to stimulate muscle maintenance and growth.
Timing: As you age there is a greater need to distribute the protein equally across 3 daily meals. Therefore, 20 grams of protein 3 times per day would be ideal. Exercise should be in close proximity to one or more of these feedings.
Research has demonstrated that low load high intensity lifting at 30% of the one repetition max (1RM) to failure can elicit similar rates of muscle protein synthesis as traditional, high load low intensity lifting at 90% of 1RM. Data suggests that low and high load lifting performed to failure yield equivalent hypertrophy over time. So exercise volume (repetitions x sets x load) can achieve maximal muscle fiber activation, including the important larger type II fibers. This is also much less likely to cause injury, an important consideration at any age.
Bottom line: shoot for less weight, more reps, more sets and failure. I prefer body weight exercises outdoors that introduce a balance component (and snow in winter) to keep you focused.