Negative Impact of Icing Treatment on Qualitative Recovery of Injured Soleus Muscle in Rats: 2992 Board #38 May 31 2:00 PM - 3:30 PM

PURPOSE: Although the RICE (Rest, Ice, Compression, and Elevation) treatment has been recognized as the gold standard of first aid treatment for sports injuries, we and the others previously demonstrated that a transient icing treatment immediately after skeletal muscle injury impaired muscle regeneration. However, the information about the influence of icing treatment following skeletal muscle injury remains limited. This study was, therefore, to investigate the impact of icing as a first-aid treatment on qualitative recovery of damaged muscle in terms of fibrosis and myosin heavy chain (MyHC) profile. METHODS: Male Wistar rats (9-10 weeks of age) were randomly assigned to control (Con), injured, and injured with icing groups (Ice). Bupivacaine (BPVC) was injected into slow soleus muscles bilaterally in order to induce muscle injury in the two injury groups. Application of icing treatment (ice pack, 0°C for 20 min) to the icing group was carried out immediately after the BPVC injection. At 3 days-4 weeks after BPVC injection, soleus muscles were removed and analyzed. RESULTS: Compared with the Con group, a significant increase in fibrotic area was observed after 2 weeks following injury in the injured groups, but after 1 week following injury in the Ice group (P < 0.05). This area was also tended to be higher in Ice than in injured animals during 1-4 weeks of recovery period. In addition, the number of Tcf4-positive nuclei, a fibroblast marker, located in interstitial spaces in both injured groups markedly increased 1 week after BPVC injection. The numbers were tended to be more magnified in the Ice group than in the injured group, then their number in both injured groups gradually degreased thereafter. Injury-related de novo appearance of embryonic, neonatal, IId/x, and IIb MyHC isoforms was noted in both injured groups 1 week after BPVC injection. These MyHC isoforms were significantly decreased toward the undetectable level thereafter. However, the embryonic MyHC isoform was still detectable in icing, but not in injured, animals 4 weeks after BPVC injection. CONCLUSIONS: Our results suggested that icing treatment following skeletal muscle injury will have a negative impact on recovery process (fibrosis and normalization of MyHC profile) of regenerating muscle.