Researchers who placed tiny ice packs on the back legs of mice after simulated workouts say they have new evidence that putting ice on sore muscles might be a bad idea. The researchers say they used electrical stimulation to simulate a grueling workout in 40 mice, and tissues from the un-iced mice healed a lot faster than the ones who had the packs applied, the New York Times reports. In the un-iced samples, pro-inflammatory cells removed damaged tissue. They were followed by anti-inflammatory cells and after two weeks, the muscles were fully healed. In the iced mice, the process was a lot slower and there were still indications of tissue damage and fewer regenerating fibers at the end of two weeks. "These findings suggest that icing following muscle damage blunts the efficiency of muscle regeneration," the authors write.
The study published in the Journal of Applied Physiology follows several previous studies that concluded icing sports or workout injuries led to slower healing, the Times notes. "In our experimental situation, icing retards healthy inflammatory responses," says study co-author Takamitsu Arakawa of Kobe University. Arakawa points out a couple of limitations with the experiment: Mice muscles are similar to our own but clearly not identical, and the muscle damage the mice experienced was more of the severity you'd see with a strain or tear, rather than general soreness. The team plans follow-up studies looking at how the process plays out in people who experience lesser levels of damage. (Read more sports injuries stories.)