Exercise Protects Muscle and Nerves from Reperfusion Injury

After five weeks of treadmill running, the mice were subjected to local ischemia by unilateral application of a rubber band tourniquet above the femur for one hour. Following reperfusion, the researchers measured oxidative stress to the cell’s mitochondria.

The IR after tourniquet release caused significant muscle injury and denervation at the neuromuscular junction (NMJ), depressed muscle strength, and neuromuscular transmission in both the sedentary and exercise-trained mice alike. But despite the similar degree of muscle atrophy and oxidative stress, the exercise-trained mice suffered reduced muscle injury and denervation at the NMJ, and improved regeneration and functional recovery following IR. The study was published on November 15, 2018, in the Journal of Applied Physiology.

“Exercise-trained mice had a much better recovery, evidenced by less nerve damage, less muscle damage, and less reduction of contractile function in the muscle immediately after injury and days later,” said senior author Zhen Yan, PhD, director of the UVA Center for Skeletal Muscle Research. “These data suggest that endurance exercise training preserves motor nerve and myofiber structure and function from IR injury and promote functional regeneration.”

“Because of the damage caused by reperfusion injury, doctors now seek to limit the amount of time blood flow is cut off to no more than 90 minutes,” concluded Dr. Yan. “The way we often do that is by putting on a tourniquet to completely stop circulation until the patient can be taken to the emergency room. But there's an issue there: We cannot block it too long; the tissues will be dead. We have to restore the blood flow at some point, but it will cause reperfusion injury. There is a conundrum.”

Ischemia-reperfusion due to temporary restriction of blood flow causes tissue or organ damages under various disease conditions, including stroke, myocardial infarction (MI), trauma, and orthopedic surgery. In the limbs, IR injury to motor nerves and muscle fibers causes reduced mobility and quality of life.

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