While exercise is primarily valued for its influence on physical health, strength and mobility, there’s ample evidence showing physical exercise, especially strength training, is just as important for healthy brain and nervous system function. A number of studies, which I’ll review below, have linked muscle strength, and leg strength in particular, to various cognitive benefits.
This fascinating link was again demonstrated in a recent study1,2 published in Frontiers in Neuroscience, which shows that neurological health is as dependent on signals from your large leg muscles as it is on signals from your brain to your muscles. In other words, it’s a two-way street, and neither “lane” is more important than the other. As noted by the authors:
“Both astronauts and patients affected by chronic movement-limiting pathologies face impairment in muscle and/or brain performance. Increased patient survival expectations and the expected longer stays in space by astronauts may result in prolonged motor deprivation and consequent pathological effects.
Severe movement limitation can influence not only the motor and metabolic systems but also the nervous system, altering neurogenesis and the interaction between motoneurons and muscle cells. Little information is yet available about the effect of prolonged muscle disuse on neural stem cells characteristics. Our in vitro study aims to fill this gap by focusing on the biological and molecular properties of neural stem cells (NSCs) …
The overall results support the existence of a link between reduction of exercise and muscle disuse and metabolism in the brain and thus represent valuable new information that could clarify how circumstances such as the absence of load and the lack of movement that occurs in people with some neurological diseases, may affect the properties of NSCs and contribute to the negative manifestations of these conditions.”
The Importance of Leg Exercise for Brain and Nervous System Health
According to the press release,3 the finding “fundamentally alters brain and nervous system medicine — giving doctors new clues as to why patients with motor neuron disease, multiple sclerosis, spinal muscular atrophy and other neurological diseases often rapidly decline when their movement becomes limited.”
In other words, whenever you’re unable to perform load-bearing exercises, you not only lose muscle mass due to muscle atrophy, your body chemistry is impacted in such a way that your nervous system and brain also begin to deteriorate. To reach this conclusion, the researchers prevented mice from using their hind legs for 28 days. The animals could still use their front legs, however, and were able to eat and groom normally without getting stressed.
At the end of 28 days, the sub-ventricular zone of the animals’ brains was examined. This is an area of the brain responsible for the health of nerve cells. Remarkably, neural stem cells — undifferentiated stem cells that can develop into both neurons and other brain cells — had declined by 70 percent in the animals that had not used their hind legs, compared to unhindered controls. Neurons and oligodendrocytes (glial cells that insulate nerve cells) also failed to fully mature in the treatment group. According to the press release:4
“The research shows that using the legs, particularly in weight-bearing exercise, sends signals to the brain that are vital for the production of healthy neural cells, essential for the brain and nervous system. Cutting back on exercise makes it difficult for the body to produce new nerve cells — some of the very building blocks that allow us to handle stress and adapt to challenge in our lives.”
Your Body Was Made for Weight Bearing
What’s more, by not using the leg muscles, two genes were adversely impacted. One of them, known as CDK5Rap1, plays an important role in mitochondrial health and function, which is yet another important reason for getting weight-bearing exercise.
As you may be aware by now, healthy, well-functioning mitochondria are crucial for optimal health, and mitochondrial dysfunction is a root cause of virtually all chronic disease, including neurodegeneration, as your brain requires the most energy of any organ — about 20 percent of the energy generated in your entire body.
As noted by lead author Dr. Raffaella Adami,5 “It is no accident that we are meant to be active: to walk, run, crouch to sit, and use our leg muscles to lift things. Neurological health is not a one-way street with the brain telling the muscles ‘lift,’ ‘walk,’ and so on.” Previous research fully supports the notion that muscle use plays an enormously important role in brain health.
Indeed, weight-bearing against gravity itself is a crucial component of life that allows the human body and brain to function optimally. This has been clearly elucidated by Joan Vernikos, Ph.D., former director of NASA’s Life Sciences Division, in her book “Sitting Kills, Moving Heals.”
How Stronger Muscles Benefit Your Brain
Previous research has shown exercise is a key way to protect, maintain and improve your brain healthand optimize your cognitive capacity. It’s even been shown to help fight dementia. There are a number of different mechanisms behind this body-brain link. One, perhaps key, factor is related to how exercise affects brain-derived neurotrophic factor (BDNF), which is found in both your muscles and your brain.
Exercise initially stimulates the production of a protein called FNDC5. This protein in turn triggers the production of BDNF, which is a remarkable brain and muscle rejuvenator. In your brain, BDNF helps preserve existing brain cells,6 activate brain stem cells to convert into new neurons (neurogenesis) and promote actual brain growth, especially in the hippocampus area; a region associated with memory.
In your neuromuscular system, BDNF protects your neuromotor, the most critical element in your muscle, from degradation. Without the neuromotor, your muscle is like an engine without ignition. Neuromotor degradation is part of the process that explains age-related muscle atrophy.
Yet another mechanism at play here relates to a substance called β-hydroxybutyrate, which your liver produces when your metabolism is optimized to burn fat as a primary fuel.7 When your blood sugar level declines, β-hydroxybutyrate serves as an alternative source of energy. β-hydroxybutyrate is also a histone deacetylase inhibitor that limits the production of BDNF.8
So, your body appears to be designed to improve BDNF production via a number of different pathways in response to physical exertion, and BDNF’s cross-connection between your muscles and your brain helps explain why a physical workout can have such a beneficial impact on both muscle and brain tissue. It, quite literally, helps prevent and even reverse brain decay as much as it prevents and reverses age-related muscle decay. Exercise also helps protect and improve your brain function by:
- Improving and increasing blood flow (oxygenation) to your brain
- Increasing production of nerve-protecting compounds
- Reducing damaging plaques in your brain, and
- Altering the way these damaging proteins reside inside your brain, which appears to slow the development of Alzheimer’s disease
Studies Demonstrating Muscle-Brain Link
Here’s a sampling of studies demonstrating this fascinating muscle-brain link:
|In a 2011 study,9 seniors who walked 30 to 45 minutes, three days per week for one year, increased the volume of their hippocampus by 2 percent. Typically, your hippocampus tends to shrink with age. The results prompted the authors to claim exercise is “one of the most promising nonpharmaceutical treatments to improve brain health.”|
|Research10 also shows exercise helps preserve gray and white matter in your frontal, temporal and parietal cortexes, which also helps prevent cognitive deterioration.|
|A 2016 study11 in the journal Gerontology found that working your leg muscles helps maintain cognitive function as you get older. According to the authors, simply walking more could help maintain brain function well into old age. The study followed 324 female twins, aged 43 to 73, for a decade. Cognitive function such as learning and memory was tested at the outset and at the conclusion of the study.
Interestingly, leg strength was found to be a better predictor for brain health than any other lifestyle factor they reviewed. Consistently, the twin with the greatest leg strength maintained higher cognitive functioning over time compared to her weaker twin. The stronger of the pair also experienced fewer age-related brain changes over time.
|A Georgia Tech study12 (featured in the video below) found that 20 minutes of strength training enhanced long-term memory by about 10 percent. In this experiment, 46 volunteers were randomly assigned to one of two groups — one active and one passive. Initially, all of the participants viewed a series of 90 images. Afterward, they were asked to recall as many images as they could.
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