Low-Intensity Vibration as a Treatment for Traumatic Muscle Injury

Traumatic muscle injuries are a devastating consequence of motor vehicle accidents, limb salvage surgeries for the removal of tumors and military combat. These injuries are characterized by a significant loss of tissue and inadequate healing leading to impaired muscle function, joint stiffness, and loss of mobility. Low-intensity vibration (LIV) is a promising candidate for physical therapy that provides mechanical stimulation without requiring active muscle contraction. The goal of this study was to determine if LIV improves the healing of injured muscle and if these effects are mediated by IGF-1 and associated downstream pathways using a mouse model of laceration injury and a cell culture model of myoblast differentiation. We found that whole-body LIV (WBV) at 45 Hz and 0.4g increased myofiber area, while WBV at 90 Hz and 0.2g increased both myofiber area and diameter at day 14 in a mouse model of laceration injury. Additionally, we showed that local LIV at 90 Hz and 0.2g increased both myofiber area and diameter in injured muscle at day 14 post-injury while also increasing percent area of peripherally-nucleated myofibers (associated with mature muscle) and decreasing percent damaged area. These LIV-induced effects on muscle were not associated with an increase in IGF-1 protein or mRNA expression. Furthermore, LIV also increased differentiation and growth of cultured myotubes at day 6 post-differentiation. There was an increase in total Akt in muscle at the day 7 post-injury and in cultured myotubes at day 3 post-differentiation while, phosphorylated to total Akt ratio increased at day 14 post-injury in muscle and at day 6 post-differentiation in cultured myotubes. Taken together, LIV enhances growth of myofibers following laceration injury, muscle cells are capable of directly transducing LIV signals into enhanced differentiation and growth, and Akt may be involved in this process. Therefore, LIV could be a promising therapeutic option for the healing of traumatic muscle injury.