Vibrations and physical strain – a dangerous cocktail

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Vibrations, physical strain and stress. Different work environment factors can act in unison to form a dangerous cocktail that increases the risk of occupational injuries.

There are a number of well-known health risks to take into account on board ships. These include heavy lifting, stress, vibration, awkward working positions and chemicals, to name but a few. Research shows that if people are exposed to several unhealthy factors at the same time, their effects may be multiplied and increase the risk of occupational injuries. One such dangerous combination is physical strain and vibrations from hand-held tools. Eva Jangdin is an ergonomist at the Occupational and Environmental Health Clinic at the Örebro University Hospital, and has many years of experience with patients exposed to this type of combined strain disorders.

Nerves and joints
–“Vibrations are kinetic energy that is propagated in the body, and people often tense their muscles more when working with vibrating hand tools compared with non-vibrating tools. If you also have a poor working position, stress on the body is even greater,” says Eva Jangdin.

The combined strain results in tense muscles, at the same time as nerves and joints are affected. Blood flow decreases in the muscles and sensation in fingers and hands may be reduced. To compensate for the loss of sensation, people often hold the tool even harder – which only adds to the negative effect. One example of an injury that can be linked with vibrating tools and physical strain is carpal tunnel syndrome. Common signs and symptoms are numbness and pins and needles in the hands and fingers, especially at night. There may also be reduced sensation in the fingers, and an operation may be required to remedy the symptoms. Other problems associated with vibration injuries and physical strain are osteoarthritis in the finger joints, aches in the arms and reduced strength despite the same muscle volume. There are other factors that may contribute to increased strain when working with vibrating hand tools, including whole body vibration. Standing on a shaking deck and chipping rust with a bent back under static muscle strain can cause pain in the back and arms.

”Whole body vibrations are propagated through the floor into the body, often resulting in problems in the lower back and the neck. The fact that feet are not affected by whole body vibrations in the same way as hands are by hand-held tools is because they are often better protected by the outer sole of the shoes,” says Eva Jangdin.

But you should be careful about reducing vibration exposure to the hands by using thicker gloves, according to Eva Jangdin.

”Thick gloves reduce the sensations in the hands and may make you hold the hand tool even harder, which increases exposure to vibration. There are special vibration-protecting gloves, but we don’t like to recommend them since they can give a false sense of security and make you think you can work for longer than the recommended time.”

Other factors that may make working with hand-held tools even worse are low temperatures and stress. Superficial blood vessels constrict when they get cold, resulting in lower blood circulation and poorer muscle function. Stress is harmful in several ways.

Reduces deep breathing
”When we become stressed, the body reacts by tensing the muscles and preparing for fight or flight. We can manage this for a short while, of course, but if we work under long-term stress we do not breathe deeply and the amount of oxygen in the blood and muscles is reduced, which makes them tired. This results in a higher risk of strain injuries. Stress also affects our cognitive abilities, which increases the risk of accidents at work, says Eva Jangdin.

Linda Sundgren

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