Massage may be a relief for sore, injured muscles but new research suggests it could also make them stronger and heal quicker.
Scientists used a custom-designed robotic system to effectively massage the leg muscles of mice.
They found that this rapidly cleared immune cells called neutrophils out of severely injured muscle tissue.
The process also removed inflammatory proteins released by the cells from the muscles, enhancing the process of muscle fibre regeneration, the study found.
First author Bo Ri Seo, of the University of Harvard’s Wyss Institute and John A Paulson School of Engineering and Applied Sciences (SEAS), said: “Lots of people have been trying to study the beneficial effects of massage and other mechanotherapies on the body, but up to this point it hadn’t been done in a systematic, reproducible way.
“Our work shows a very clear connection between mechanical stimulation and immune function.
“This has promise for regenerating a wide variety of tissues including bone, tendon, hair, and skin, and can also be used in patients with diseases that prevent the use of drug-based interventions.”
Several years ago the researchers started exploring the effects of mechanotherapy on injured tissues in mice.
They found that it doubled the rate of muscle regeneration and reduced tissue scarring over the course of two weeks.
Based on their findings, the team decided to look into exactly how that process worked in the body, and to figure out what would maximise healing.
Working with soft robotics experts in the Harvard Biodesign Lab, they created a small device that monitors and controls the force applied to the limb of a mouse.
Repeated force was applied to injured muscles for 14 days, and while both treated and untreated muscles displayed a reduction in the amount of damaged fibres, the reduction was more pronounced in the treated muscle, researchers found.
The cross-sectional area of the fibres was also larger in the treated muscle, indicating that treatment had led to greater repair and strength recovery.
According to the study, the greater the force applied during treatment, the stronger the injured muscles became, suggesting that mechanotherapy improves muscle recovery after injury.
Scientists performed a detailed biological assessment, analysing a wide range of inflammation-related factors called cytokines and chemokines in untreated and treated muscles.
They found that a subset of cytokines was dramatically lower in treated muscles after three days of mechanotherapy.
These small proteins are associated with the movement of immune cells called neutrophils, which play many roles in the inflammation process.
Researchers found that treated muscles also had fewer neutrophils in their tissue than untreated muscles, suggesting the reduction in cytokines that attract them had caused the decrease in neutrophil infiltration.
They hope to continue the research in larger animals, with the goal of being able to test the efficacy of the mechanotherapeutic approach on humans.
They also hope to test it on different types of injuries, age-related muscle loss, and muscle performance enhancement.
“The fields of mechanotherapy and immunotherapy rarely interact with each other, but this work is a testament to how crucial it is to consider both physical and biological elements when studying and working to improve human health,” said David Mooney, corresponding author of the paper.
The research is published in Science Translational Medicine.
