Frequent Icing Stimulates Skeletal Muscle Regeneration Following Injury With Necrosis in a Small Fraction of Myofibers in Rats

Icing interventions on the injured skeletal muscle affect the macrophage-related regenerative events and muscle repair. However, despite its importance for the practice in sport medicine, the influence of different icing protocols on muscle regeneration remains unclear. Here, using a rodent model of mild muscle injury with necrosis in a small fraction of myofibers, the injured animals were allocated to four groups: non-icing control (Con) and a single treatment (Ice-1), three treatments (Ice-3), or nine treatments (Ice-9) with a 30-min icing each time within two days following injury. Muscle regeneration was compared between the groups on post-injury days 1, 3, 5, and 7. The results showed that compared with the Con group, muscle regeneration was faster in the Ice-9 group (but not in the Ice-1 and Ice-3 groups), as indicated by more rapid accumulation of satellite cells within the regenerating area and enlarged size of regenerating myofibers (p<0.05, respectively). There was also less macrophage accumulation (p<0.05) and a trend toward early removal of necrotic myofibers in the damaged/regenerating area in the Ice-9 group (p=0.0535). These results demonstrate that in the case of mild muscle damage, more frequent icing treatment is more effective to stimulate muscle regeneration.