Your Body and Brain in Motion Are Where Mind and Matter Meet

The mechanical stresses of muscle activity are major cues for neuroplasticity.

Reviewed by Davia Sills

Key points

• Physical activity is a critical determinant for regulating overall health as a human animal in the world.
• Physical activity leads to biochemical cascades with neurobiological benefits.
• Muscle activity associated with movement may produce independent cascades that are synergistic.

Typically when we hear "neuroplasticity," we imagine neural excitability, circulating signaling mechanisms, and connectivity. Neurobiological and biochemical, for sure, but maybe not mechanical changes. Yet movement is a fundamental property of being an animal, and the movement itself may help reinforce moving about.

Spinal cord slinky

Way back when I was doing my Ph.D., I was in a seminar on neuroplasticity. One of the other trainees asked the professor an interesting question—how elastic is the spinal cord? Obviously, lots of spinal cord injuries arise from exceeding biological limits, but they went on to explain that they wondered how the spinal cord got longer as we grew up from childhood and how we are able to bend and twist the way we do. It was an interesting question with very little data to explain what was obvious—there's a link between our activity and the physical properties of our nervous system.

Similarly, when we think of the benefits of physical exercise, the first things that may come to mind are probably heart rate changes, the pumping of blood, the release of circulating hormones like adrenaline, and the stimulation of the release of brain-derived neurotrophic factor (BDNF). Although the commands come from brain and spinal cord motor neurons, when we activate our muscles, mechanical forces are produced. These affect the muscle itself, tendon, bone, and beyond. But does this feedback somehow affect the things commanding the contractions?

Neuromechanical interactions between muscle and mind

Angel Bu, Ferdows Afghah, Nicolas Castro, Maheera Bawa, Sonika Kohli, Karina Shah, Brandon Rios, Vincent Butty, and Ritu Rama at MIT in Cambridge did a very clever set of tissue-engineering experiments. They really wanted to understand how the signaling of mechanical action in muscle might alter the properties of the neurons sending the commands for those actions. This is a very difficult thing to unwind in "intact" animals because of the extensive and reciprocal biochemical and neurohormonal signaling pathways. In their study in Advanced Healthcare Materials, they leveraged the power of in vitro cellular preparations using well-known stem cell techniques to study the issue and get a clear answer.

Studying the properties of fundamental cellular constituents of muscle, they showed that "tuning the mechanical properties...of highly contractile skeletal muscle monolayers" produced "muscle-secreted factors significantly upregulate neurite outgrowth and migration." What this means is that the signaling pathways related to just the actual mechanical contraction of muscle stimulated neuroplastic changes in the properties of the motor neurons that would command such contractions.

Interestingly, this effect scaled with "muscle contraction intensity." This was similar in scale to biochemical factors but did not affect gene expression. This highlights the important overlap of multiple pathways present in real-world living animals.

You are an integrated animal

Of course, all of this makes sense if we truly appreciate the integrated nature of physiology. Literally all systems interact and communicate to produce healthy behavior. This underscores the implications for further understanding how movement affects overall mental and physical health.

Although the primary scientific evidence above comes from an extremely reduced cellular preparation, it has big implications for integrated human behavior. The main take-home message is that everything is connected. Our efforts to improve, no matter how small, can generate multiple cascading responses within our bodies that can lead to better neurobiological and psychological health. Please take those steps towards your own future, knowing that just by taking each one, you are triggering brain and body benefits.

(c) E. Paul Zehr (2024)