Get moving! Exercise decreases inflammation, facilitates wound healing

Jun 01, 2008, 4:00am

The benefits of exercise to wound healing have been linked for the first time to decreased inflammation. The study was conducted in mice at the University of Illinois at Urbana-Champaign and published in the American Journal of Physiology: Regulatory, Integrative and Comparative Physiology.

Key Points

National Report - The benefits of exercise to wound healing have been linked for the first time to decreased inflammation, according to a study that was conducted in mice at the University of Illinois at Urbana-Champaign and published in the American Journal of Physiology: Regulatory, Integrative and Comparative Physiology.

A growing body of research has established that lower levels of inflammation are associated with faster wound healing and less scarring in mammals.

Fetal tissue repairs itself remarkably well, but the skin's capacity to heal declines with age.

He formed the hypothesis that moderate exercise might speed wound healing by decreasing the level of proinflammatory cytokines that are associated with aging, and set out to test it in the mouse model.

To control the amount of exercise, he ran the study animals on a motorized treadmill for 30 minutes both before and during wound healing, while the control animals had no opportunity for exercise.

A skin biopsy instrument was used to create four full-thickness dermal wounds, and the rate of wound closure was assessed over 10 days. The process was repeated four months later, with the wounds harvested at one, three and five days and the levels of cytokines measured.

"The old mice that exercised healed faster than the old mice that did not exercise," and the difference was significant (p<0.05), Dr. Keylock tells Dermatology Times.

Analyzing the wounds, he found significantly (p<0.05) lower levels of tumor necrosis factor alpha (TNF-alpha), keratinocyte chemoattractant (KC), and monocyte chemoattractant protein-1 (MCP-1) in the older animals that exercised.

"All of the young animals had lower levels of inflammation, whether they exercised or not. And exercise brought the levels of inflammation in the older mice down to levels that were similar to, but not quite as low, as those seen in the younger animals.

"We didn't report that in the study because we didn't test enough young mice" to adequately power that outcome, Dr. Keylock says.

He says the benefits of exercise on wound healing occur early in that process, up to six days post-wounding. The time to 20 percent closure was 2.5 days faster in the aged exercised mice; the time to 80 percent closure was 51 percent faster.

Dr. Keylock says researchers selected moderate exercise for the study "because we thought we would see larger reductions in inflammation that way."

The exercise the mice received corresponds with a human taking a brisk walk for 30 minutes a day, five to six times a week.

He thinks it likely that a certain minimal amount of exercise, possibly less than that in this study, is necessary to generate the healing benefits. But after that is achieved, the benefits are likely to plateau, and more exercise is not going to result in a significantly greater benefit.

Physicians should encourage their older patients to do regular aerobic exercise prior to and after surgery. He says, "It will help their wound heal faster and decrease the likelihood of scarring," in addition to all of the other benefits of exercise, such as improving strength, muscle tone, and bone density, and decreasing body fat.

Dr. Keylock believes these findings will have application for other conditions with high levels of inflammation, such as diabetes and obesity; exercise is likely to improve wound healing in these patients, as well. His future research will look at these issues in a diabetic population.

Inflammation is a double-edged sword in wound healing - it can help and it can damage.

"It is important to understand what kinds of cells are involved and what mediators are produced by these cells," says Zofia Zukowska, M.D., Ph.D., chairman of the department of physiology and biophysics, Georgetown University School of Medicine.

"Macrophages are very necessary for new blood vessel formation. Removing them the wound environment may impair wound healing. It's not an absolute that inhibiting inflammation would be helpful to wound healing.

"Exercise by itself has been shown to improve vascularization, so it's not surprising that it has beneficial (effects) in improving blood flow to the wound and washing out toxic elements to improve wound healing," she says.