After a particularly strenuous workout or sports injury, many of us rely on ice packs to reduce muscle soreness and swelling.but a Cautionary New Animal Research The icing was found to alter the molecular environment inside injured muscles in harmful ways, slowing healing. The study involved mice, not people, but adds to a growing body of evidence that muscle icing after strenuous exercise isn’t just ineffective; it can backfire.
Check the freezer or freezer in most gyms, locker rooms, or athletes’ kitchens and you’ll find ice packs. Almost as common as water bottles, they are often tied to aching extremities after strenuous exercise or possible injury. The reason for cooling is obvious. Ice cubes numb the affected area, reduce pain, and prevent swelling and inflammation, which many athletes believe helps their sore muscles heal faster.
In recent years, however, exercise scientists have begun pouring cold water on the supposed benefits of ice packs.in a A 2011 study, For example, those iced torn calf muscle Later they felt as much pain in their legs as those who were left alone with their sore legs, and they were unable to return to work or other activities as quickly as possible.Likewise, a 2012 scientific review ends Athletes who ice sore muscles after strenuous exercise—or, for those with masochism, immersion in an ice bath—recover muscle strength and strength slower than their unfrozen teammates .one left Sobering 2015 Weight Training Study Men who regularly used ice packs after a workout were found to have worse muscle strength, size, and stamina than men who didn’t recover from ice packs.
But little is known about how ice actually affects sore, damaged muscles on a microscopic level. When we ice these tissues, what happens deep within them, and how could any molecular changes there affect and possibly hinder muscle recovery?
So for the new study, published in March in the Journal of Applied Physiology, researchers at Kobe University and other institutions in Japan, long interested in muscle physiology, collected 40 young, healthy males. mouse. Then, by repeatedly contracting the calf muscles through electrical stimulation of the animals’ calves, they actually simulated a long, exhausting leg day in the gym that eventually led to muscle tearing.
Rodent muscles, like ours, are made up of fibers that can stretch and contract with any movement. Overload these fibers during unfamiliar or unusually strenuous activity and you can damage them. After healing, the affected muscle and its fibers should be stronger and better able to withstand the same amount of force the next time you work out.
But now researchers are interested in the healing process itself, and whether freezing changes it. So they took muscle samples from some of the animals immediately after the simulated exercise, and then tied tiny ice packs to the legs of about half of the mice, leaving the rest unrefrigerated. For the next two weeks, the scientists continued to collect muscle samples from the two groups of mice every few hours and days later.
They then examined all the tissues with a microscope, paying particular attention to what might be happening to inflammatory cells. As most of us know, inflammation is the body’s first response to any infection or injury, with pro-inflammatory immune cells flocking to infected areas, where they fight off invading bacteria or clear damaged tissue and cellular debris. Anti-inflammatory cells then enter, quelling the inflammatory response, and promoting healthy new tissue formation. But inflammation is often accompanied by pain and swelling, which is understandable, and many people dislike and use ice to reduce pain and swelling.
By looking at the mouse leg muscles, the researchers found clear evidence of damage to many of the muscle fibers. They also noticed that in the unfrozen tissue, pro-inflammatory cells rapidly clustered. Within a few hours, the cells were busy removing cellular debris, and by the third day after contraction, most of the damaged fibers had been removed. At that point, anti-inflammatory cells appeared, along with specialized muscle cells that rebuild tissue, and by two weeks the muscles appeared to be fully healed.
This is not the case in iced muscles, where recovery appears to be significantly delayed. It took 7 days for pro-inflammatory cells in these tissues to reach the same levels of pro-inflammatory cells as the third day in unfrozen muscle, and the clearance of debris and arrival of anti-inflammatory cells was similarly slowed. Even after two weeks, the muscles showed lingering tissue damage and molecular signs of incomplete healing.
The result of these data is that “in our experimental situation, freezing impedes a healthy inflammatory response,” said Takamitsu Arakawa, a professor of medicine at Kobe University’s Graduate School of Health Sciences who led the new study.
But, as Dr. Arakawa points out, their experimental model simulates severe muscle injury, such as a strain or tear, rather than simple soreness or fatigue. Obviously, this study also involved mice, which are not humans, even though our muscles have a similar makeup. In future studies, Dr. Arakawa and his colleagues plan to study milder muscle damage in animals and humans.
But for now, his findings suggest, he said, that damaged, sore muscles know how to heal themselves, and our best response is to calm down and put an ice pack in a cool place.