It is a common practice to massage your muscles when they are injured or sore; even devices like the massage guns are frequently used by athletes and individuals who often experience such symptoms. However, not many know how, or even if, massaging helps in effective muscle recovery. Does it increase the rate and improve the quality of healing? If so, how?
Researchers of Harvard’s Wyss Institute for Biologically Inspired Engineering and John A. Paulson School of Engineering and Applied Sciences recently issued a study regarding the effect of massaging on muscle recovery. Published in Science Translational Medicine, the study involves mice, their leg muscles, and mechanotherapy. A robotic system, designed for consistent and adjustable compressive forces, is applied onto mice’s leg muscles, which clears the injured muscle tissue of immune cells called neutrophils. These neutrophils are responsible for releasing cytokines, or proteins that regulate immunity and inflammation, and these cytokines are also removed from the tissues with this mechanotherapy. Lead author Bori Seo, Ph.D., states that this study “shows a very clear connection between mechanical stimulation and immune function” and that it has “promise for regenerating a wide variety of tissues…and can also be used in patients with diseases that prevent the use of drug-based interventions”.
For the robotic system, the research was extended to the Harvard Biodesign Lab for maximum efficiency in creating a device that would accurately display results for the study. As previously mentioned, the device was responsible for applying consistent and adjustable compressive forces to the mice’s leg muscles. As the force was adjusted, the team recorded the tissue’s response by observing the ultrasound; there was 10 to 40% strain on the muscles, signifying that the devices were transferring mechanical force. The experiment was repeated for 14 days and the team had stable results: lower amounts of damaged muscle fibers, but with more clarity and relatively larger size, compared to the control set of muscles without treatment.
Additional research was also conducted to determine what exactly caused the mechanical force to aid muscle recovery. They were able to discover that neutrophil activates muscle cell growth while excessive exposure to this factor impairs it instead. Besides the generally known function of neutrophils—to kill and clear out pathogens and damaged tissue, Seo and other scientists were able to recognize how it directly impacts muscle cells. Moreover, it was confirmed that the removal of neutrophils benefited muscle recovery and promoted a faster process. As Walsh, a Paul A. Maeder Professor of Engineering and Applied Science at SEAS, commented, this ‘provides great motivation for the development of external, mechanical interventions to help accelerate and improve muscle and tissue healing that have the potential to be rapidly translated to the clinic”.