New Study Links Muscle Wasting to… Nerves

Did you know that a healthy person has an average of 60,000–70,000 nerves controlling their legs? Did you also know that number takes a 30% hit by the time you turn 75?

It’s true! A study published earlier this month in the Journal of Physiology looked at how and why muscle mass wastes away with age. That’s when they made the connection between muscle wasting and the nerves that connect the lumbar region of the spine to the legs.

The idea of muscle loss with age has been acknowledged for a while now, but it took until now for researchers to pin down the “why.”

The study included 168 men and made the discovery using MRIs while looking at the femur bone and surrounding muscle.

The researchers found that when the nerves connecting the spine to the legs began to deteriorate, it left significant amounts of muscle functionally useless. Without a connection to the nervous system, those muscles aren’t triggered and end up wasting away.

These deteriorating muscles lead to the weakness and instability commonly seen in older folks. This weakness is a condition known as sarcopenia and affects an estimated 10–20% of people aged over the age of 65.

What they also found was that large, healthy muscles had a form of protection against this. Fit muscles are able to send out new branches of nerves after old ones have deteriorated and “rescue” the surrounding tissue. Because new nerve endings start to appear throughout the muscle, the muscle continues to receive signals from the nervous system. This continues to trigger the muscle, which means it’s able to stave off deterioration.

All that roughly translates into: healthy muscles will continue to be healthy, while weak muscles will continue to be weak.

It’s pretty much Newton’s first law, or the law of inertia: an object at rest stays at rest, while an object in motion stays in motion. Except that object is your thigh muscle.

In the last decade or so, the overall understanding of how bone and muscle interact with each other has grown. The tissues are constantly interacting and have similar responses to things like inflammation and growth hormones. What this means is that osteoporosis and sarcopenia could be more closely connected than we realized.

Sarcopenia is a symptom of frailty, which is a leading cause of falls, and therefore fractures. Along with muscle wasting, frailty is characterized by nutritional deficiencies, loss of balance and gait, and cognitive impairment. That combination is a recipe for injury and fracture.

And that makes sense, given what we already know about the impact of weight-bearing exercise on bone health. There’s a clear connection between strong muscles and healthy bones.

The good news is that this means muscle wasting is preventable. Research shows that physical activity can help stave off sarcopenia, similar to the impact of exercise on osteoporosis. Regular workouts also play a huge role in maintaining overall good health, balance, and bone density into old age.

If you’re looking to get out of the house, look for programs you can join, like group yoga or a walking clinic. Start gradually, find something you love, and partner up with a workout buddy.

My wife, Viv, and I love going for walks together. It’s a great chance for us to connect while getting our muscles moving. Exercising with a partner turns workouts into social time, plus you’ll get the added benefit of helping a friend stave off muscle deterioration.

Exercise ideas: https://www.algaecal.com/expert-insights/category/exercise/

Sources:
http://onlinelibrary.wiley.com/doi/10.1113/JP275520/full
https://medicalxpress.com/news/2018-03-muscle-frailty-age.html
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4888925/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4972629/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5441519/