Muscle injury is a common problem in sports medicine. Myofiber regeneration and repair is often hindered by the development of fibrotic tissue, which results in incomplete functional recovery and, likely in part, a reason for re-injury. A common treatment modality following intense eccentric exercise (EEC) is massage; however, the biologic mechanisms of action for massage therapies are still unknown. Studies have shown that mechanically stimulating muscle stem cells before implantation fosters muscle healing. We propose that massage accelerates muscle healing by increasing myofiber regeneration and reducing tissue fibrosis.
PURPOSE: To determine effects of massage on regeneration and repair following EEC.
METHODS: In this pilot study, seven female New Zealand White rabbits were instrumented with bilateral peroneal nerve cuffs for stimulation of the tibialis anterior (TA) muscle. One hindlimb was randomly selected to undergo a damaging bout of EEC. Animals were randomly selected for massage application immediately following EEC, 24 hours after EEC, or 48 hours after EEC. One animal was designated as an exercised, non-massaged control. Massage was applied using a customized device for 4 consecutive days. At the end of four days of massage, animals were euthanized and the TAs excised and frozen for immunohistochemical analysis. H&E and Masson’s trichrome staining was used to determine the amount of muscle regeneration (centronucleated fibers) and fibrosis. Angiogenesis was determined by the number of CD31 positive blood vessels.
RESULTS: Massage resulted in an average 14% increase (normalized to contralateral limb) in the number of CD31 positive vessels. The number of regenerating fibers increased 3.5% with massage compared to an average 0.7% in the contralateral limb. Immediate massage was more effective than delayed massage in promoting regeneration and angiogenesis. Immediate massage was also most effective in reducing tissue fibrosis, resulting in 7% fibrotic area compared to 15% in the control.
CONCLUSIONS: Massage increases the percentage of regenerating muscle fibers, promotes angiogenesis, and decreases fibrosis following EEC injury. Immediate massage was more effective than massage delayed 48 hours for promoting tissue regeneration and reducing fibrosis.
Supported by NIH R01 AT004922 [TMB]