Contracting and exercising muscles may help nerves recover and grow after nerve damage, a new animal study has found.
During workouts, muscles release chemicals called myokines. Researchers at the Massachusetts Institute of Technology (MIT) found that motor neurons exposed to myokines grew four times more than those not exposed. Stretching the nerves to mimic the physical force of muscle contraction led to comparable growth results.
Motor neurons are nerves that help the body move. They differ from sensory neurons, which detect our senses, and cortical neurons, responsible for cognition.
The researchers said the study's findings may be promising for neurodegenerative diseases that affect motor neurons, like amyotrophic lateral sclerosis (ALS), or Lou Gehrig's disease.
Myokines are molecules that communicate with cells and tissues throughout the body, influencing various biological processes. Although muscles primarily produce myokines during exercise, other cells also release these molecules during physical activity.
Neurons exposed to the "exercise" solution showed significant increases across all measures of nerve growth: They grew over four times longer, had single projections that grew 1.5 times farther, and covered 2.9 times more area than controls.
Some lab-grown muscles also twitched spontaneously, a common behavior in muscle cultures. Researchers found that myokines from these twitching muscles also promoted neuron growth, though the exercised-muscle solution had a more substantial effect. This suggests that more intense muscle activity promotes greater neuron growth.
They grew another set of neurons and used the same gel mat, embedded with tiny magnets and activated by a magnet outside to wobble the gel back and forth. This vibrated the mat, simulating the force the neurons would experience during actual muscle contraction. They exercised the nerves 30 minutes a day for five days.
Like nerves exposed to myokines, mechanically stimulated nerves showed significant increases across all growth measures: They grew nearly three times longer, with single projections extending 1.5 times farther, and covered three times more area than the controls.
"Our study is in vitro using mouse cell lines," Raman said, adding that the team is currently adapting the mouse model to use human cells instead. She said they're "studying whether muscle-to-nerve signaling can be used to promote nerve regeneration after traumatic injury or diseases like ALS.
"If our findings are translated to human models, therapeutic muscle stimulation would likely be accomplished by implanting electrodes directly in muscle tissue," Raman added.
Nerve growth and healing are essential in treating conditions ranging from trauma-induced nerve damage to peripheral neuropathies caused by chemotherapy or metabolic issues, Michael Masi, a sports doctor and certified personal trainer at Garage Gym Reviews, who wasn't part of the study, told The Epoch Times.
In line with the study's findings, he noted that contracting muscles through their full range stimulates both biochemical and mechanical pathways supporting nerve repair. However, he cautioned, this type of exercise isn't always suitable, especially in the acute stages of healing when inflammation is present or when the nerve is severely disrupted.
In such cases, he recommends two approaches: indirect healing through exercise of unaffected limbs, which stimulates the body's natural healing processes without stressing the injured area, or gentle, targeted exercises for the injured area.
Masi said that the study suggests an "exocrine effect" from the release of myokines to promote healing at the nerves. Exocrine effects involve substances released to assist the organ from which they originate.