Healthy Living

Loud Noises Can Increase Your Risk Of Suffering A Knee Injury, Due To Brain's Confusion

Knee Injuries
Loud noises up our risk for a knee injury. Photo courtesy of Shutterstock

Recent studies have found that knee injuries are the leading cause of high school sports-related surgeries and are considered the most expensive type of sports injury. A study published in the Scandinavian Journal of Medicine & Science in Sports has revealed an unexpected source of an increased risk for knee injuries: loud noises that startle our brain circuits.

Researchers recruited 18 men and 18 women from the University of Delaware who were in their early 20s at the time of the study. Participants sat in a motorized chair that moved either leg at a controlled speed while having their dominant leg strapped at the ankle. A specifically designed arm attached to the chaired raised the knee to a 30-degree angle. During six trials, the arm slowly bent the knee to a 70-degree angle with electrodes recording thigh-muscle activity.

As the arm attached to the chair moved to bend the knee, participants were asked to resist their knee from bending as fast and hard as possible. For three out of the six trials, they wore headphones that produced a short, high-pitched beep right before the knee began to bend that was comparable to a motorcycle, The Wall Street Journal reported. The research team gauged the knee’s stiffness, the muscles ability to resist against the bend with force, and the amount of time it took.

Results found that the high-pitched beep caused a startled response that lead the muscle to stiffen in the first four degrees of bending. When that startled response dwindled, muscle stiffness and activity decreased, and the knee continued to bend to the full 70 degrees. Brain circuits in charge of neuromuscular control, which are often responsible for joint stress and unintentional injuries, in all likelihood caused the initial stiffness followed by reduced stiffness.

A recent study conducted at Center for Injury Research and Policy (CIRP) of the Research Institute at Nationwide Children's Hospital gathered data from the High School RIOTM online injury surveillance system which collects high school injury reports from the nine major sports, including boys' football, soccer, basketball, baseball and wrestling and girls' soccer, volleyball, basketball and softball. The knee was the second most frequently injured are of the body overall, mainly from boys' football and wrestling and girls' soccer and basketball.

"Knee injuries in high school athletes are a significant area for concern," Dr. Dawn Comstock, faculty member at The Ohio State University College of Medicine and one of the study authors, said in a statement. "Knee injuries accounted for nearly 45 percent of all sports injury-related surgeries in our study. Knee surgeries are often costly procedures that can require extensive and expensive post-surgery rehabilitation and can increase risk for early onset osteoarthritis. Without effective interventions, the burden of knee surgeries and rehabilitation will continue to escalate as the number of high school athletes continues to grow."

Source: DeAngelis A, Needle A, Kaminski T, Royer T, Knight C, Swanik C. An acoustic startle alters knee joint stiffness and neuromuscular control. Scandinavian Journal of Medicine & Science in Sports. 2014.

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