We all know that massage can feel very good and can have a stress-relieving benefit as well. One research study has gone further to evaluate the effects of a mechanical massage device on injured tissue. Their results were fascinating.
Researchers at Harvard's Wyss Institute for Biologically Inspired Engineering and John A. Paulson School of Engineering and Applied Sciences (SEAS) created a customized robotic system that was capable of delivering dialable, precise, compressive force to mice’s leg muscles. The rationale for the robotic device was to be able to deliver a mechanical stimulus in a systematic, reproducible way. (And let’s not forget that the researchers ARE at an engineering school.)
So they applied a consistent, repeated force to the injured mouse muscles for 14 days, and compared treated and untreated muscles. Both groups demonstrated a reduction in the amount of damaged muscle fibers, however, the reduction was more pronounced and the cross-sectional area of the fibers was laser in the treated muscles. The greater the force applied during treatment, the stronger the injured muscles became.
A subset of cytokines was dramatically lower in treated muscles after three days of mechanotherapy, and these cytokines are associated with the activation of neutrophils. Treated muscles also had fewer neutrophils in their tissue than untreated muscles, suggesting that the reduction in cytokines that attract them had caused the decrease in neutrophil infiltration.
Furthermore, the treated muscles (as well as healthy, normal muscles) had type 2X fibres present in greater numbers than the untreated-injured muscles, and less type 2A fibers. The difference, according to the researchers, explains the enlarged fiber size and greater force production of treated muscles (as type 2X fibers produce more force than 2A fibers).
The research team additionally studied the effects of depleting neutrophils in the mice on day three after injury. The treated mice’s muscle again showed larger fiber size and greater strength recovery than the untreated group. As such, they confirmed the neutrophils, while necessary in the earliest stages of injury recovery, can have an inhibitory effect on healing if they persist for too long in injured tissues.
"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 Mooney, who is the corresponding author of the paper and the Robert P. Pinkas Family Professor of Bioengineering at SEAS.
What does this mean for us?
It is a validation that manual therapies can have a positive impact on healing. WE knew that already, but it’s always good to have some research to back us up when we’re talking to the ‘non-believers’!!!
Wyss Institute for Biologically Inspired Engineering at Harvard. (2021, October 6). Massage doesn’t just make muscles feel better, it makes them heal faster and stronger: Study in mice confirms link between mechanotherapy and immunotherapy in muscle regeneration. ScienceDaily. Retrieved June 29, 2022 from www.sciencedaily.com/releases/2021/10/211006143446.htm