Exercise strengthens muscles and the heart, but new work shows working muscles also help neurons grow. A team at MIT reports that working muscle sends signals that make motor neurons, the nerve cells that control movement, grow longer and mature faster. The work used mouse cells in the lab, so it is an early step, but it offers a clear path for future nerve repair.
How muscles help neurons grow: signals from muscle
When muscles contract, they release small proteins called myokines. Myokines are chemical messengers that travel in fluid and can change how other cells behave. In the new study, researchers exercised a tiny piece of light-activated mouse muscle in a dish, collected the liquid around it, and then bathed mouse motor neurons in that liquid. The neurons grew around four times farther than those that did not receive the muscle signals, and they also switched on genes linked to maturation and communication with muscle. The MIT team describes these results in Advanced Healthcare Materials and in the matching MIT News report.
What are myokines?
Myokines are proteins made by muscle during repeated contraction. They include many different factors. Some support blood vessels and nerve growth. Reviews note that myokines and muscle vesicles help keep brain function steady across life. You can read a recent overview of how myokines from skeletal muscle help brain homeostasis.
Exercise basics
Daily movement still matters most for health. Simple guides on this site explain why walking is the simplest way to lose fat and keep it off and why, after midlife, lifting weights is the best way to slow muscle loss.
Muscle movement also guides growth mechanically
Muscle does not only send chemicals. It also moves. The team tested whether gentle, repeated movement alone could change neuron growth. They built a soft, flexible “actuating matrix” that can nudge neurons in regular cycles, without a muscle present. This purely mechanical stimulation also increased motor neuron outgrowth over five days, though gene changes were smaller than with myokines. The same paper shows how the method can be tuned to study biochemical and mechanical cues separately. MIT summarized this dual effect as exercise signals that are both biochemical and mechanical.
Why mechanics matter
Nerves live inside moving tissue. Each step, breath, and reach tugs on the cells that carry signals to muscle. Small, repeated stretches may help guide where nerve fibers grow and how they connect, especially during repair.
What this could mean for nerve repair and disease
The field hopes to help people who lose movement after severe muscle injury or nerve damage. In 2023, the same group showed that light-driven actuation of implanted muscle grafts helped mice recover near-normal function after a major muscle injury. In that work, targeted stimulation of the graft for two weeks restored movement in a way earlier passive implants did not. You can see the prior result in a peer‑reviewed study on mouse muscle grafts and in the MIT News summary.
Looking ahead, the current in‑vitro study suggests that training the muscle around an injured nerve, or delivering specific myokines, could help the nerve regrow. It may also inform ideas for diseases that kill motor neurons, like ALS. Popular science coverage explains how exercise-related myokines sped neuron growth in mouse cells.
What you can do now
These findings do not change clinical care yet. But they do support a simple habit: move most days, and include some strength work. Resistance training improves muscle health, which may raise helpful myokines during and after workouts. For brain support more broadly, see our plain guide on taking strategic breaks every 90 minutes.
Limitations and quality of evidence
- Evidence type: in‑vitro experiments using mouse skeletal muscle and mouse motor neurons; plus engineered mechanical stimulation models.
- The four‑fold growth boost and gene changes happened in dishes, not in people. No clinical outcomes were tested.
- Which myokines matter most is not yet clear. Future work must isolate and test each factor and dose.
Advanced Healthcare Materials – Actuating extracellular matrices decouple the mechanical and biochemical effects of exercise on motor neuron growth – 2024
The authors report that muscle‑secreted factors from exercised tissue markedly increase neurite outgrowth and migration in mouse motor neurons; mechanical stimulation alone also boosts growth. Evidence type: in‑vitro mouse cells.
MIT News – When muscles work out, they help neurons grow – 2024
MIT’s article explains that exercise triggers both biochemical and mechanical cues that speed motor neuron growth over five days, with quotes from study author Ritu Raman.
Nature Portfolio (PubMed) – Neuronal innervation regulates the secretion of myokines and exosomes from skeletal muscle – 2024
A review summarizes how myokines and exosomes from muscle help regulate brain and nerve function, providing context for the MIT findings.
MIT News – Light‑activated muscle grafts show promise in aiding muscle recovery post‑trauma – 2023
Earlier work from the group showed that actuated, optogenetic muscle grafts restored near‑normal function in mice within two weeks. Evidence type: in‑vivo mouse study.
Live Science – ‘Exercise juice’ released by muscles helps nerves grow, study finds – 2024
A mainstream outlet explains the study for general readers, noting that both biochemical and mechanical effects of exercise may aid nerve repair.
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