Spectator: UI investigators Study Ill Effects of Vibration on Human Body

Monday, November 15, 2010

By Travis Varner

The rattling of a tractor, the bouncing of a semitruck seat, and even the water turbulence inside the handle of a high-pressure sprayer can be more than just annoying—the vibration may be detrimental to your health.

When the human body comes into contact with mechanical environments that produce vibration, it can experience health effects ranging from minor to life-altering.

“Mechanically induced vibration can result in decreased blood flow, cause numbness, and break down connective and muscular tissue that holds everything in place,” says longtime UI spine researcher David Wilder. “These health effects can alter one’s way of life.”

Wilder is an associate professor of biomedical engineering in the College of Engineering, and with help from the UI Center for Conferences and professors Salam Rahmatalla and Nathan Fethke, he organized the third American Conference on Human Vibration, held on campus in June. Leading scientists in the field from around the world presented findings on understanding, minimizing, and eliminating vibration affecting human whole-body, hand-arm, and cellular systems from both recreational and workplace settings.

Wilder, a member of domestic (ANSI) and international (ISO) standards-setting bodies related to human exposure to vibration, has studied back problems, spine biomechanics, and vibration since the 1970s, and notes that personal health effects may not be apparent for years. When they are, he says, vibration can compromise the musculoskeletal, neuromuscular, and even cardiovascular systems, depending on its frequency.

“You can demonstrate the effect of repetitive loading or stress due to vibration, by bending a paper clip repeatedly,” Wilder explains. “If you bend it back and forth just a little bit, the clip will never break. Once you go beyond that ‘little bit,’ it has a limited life and will fail after a certain number of repeated loads. This occurs in collagen, the fibers that make up human connective tissue, as well. Numerous repeated stretching of those tissues will make them mechanically softer and weaker like the paper clip.”

One of the common results of frequent, forceful vibration is back pain.

Fredric Gerr, professor of occupational and environmental health in the UI College of Public Health, studies musculoskeletal disorders and occupational health in society. He says lower back pain may not be life threatening, but its effects on people are staggering.

“Although back pain doesn’t kill anybody, it does cause suffering, decreased quality of life, and loss of work time,” Gerr says. “Prevention of work-related back pain is a goal that will hopefully be reached.”

Back pain isn’t the only problem created by vibrations. Many hand tools cause something called hand-arm vibration syndrome, a disorder of the hands and fingers. Chainsaws and jackhammers can be devastating on one’s hands if proper safety measures aren’t followed by the manufacturers or the operators.

“Vibrations can damage the nerves of the hands, causing numbness, and can compromise the blood vessels, decreasing blood flow,” Gerr says. “Both of these effects can weaken one’s grip and decrease the effectiveness of one’s hands.”

Wilder says companies have made advances in the past decade to combat the negative effects of whole-body and hand-arm vibrations, often due to improved national and international standards and laws. For example, seats formerly rigidly fixed now bob up and down to isolate the vibrations, and some newly manufactured gloves are made to ANSI and ISO standards to isolate vibration from one’s hand.

These kinds of reforms in standards, laws, manufacturing, and workplace design demonstrate that vibration research is having a positive effect. Although there still is much left to learn, Wilder says the improvements in the field are promising and will help millions of people around the world.

“We can do all the research we want, but if we can’t get the improvements into the system, the workplace, and to the general public, then it isn’t doing any good,” Wilder says. “Continuing to see new technology that combats vibration exposure is satisfying, but the important thing to realize is there is still much to be done.”