Contact stress occurs when a worker places direct pressure on their tendons, nerves or blood vessels by resting or striking a part of their body against a hard or angled surface. It can lead to tissue damage and, over more extended periods, lead to musculoskeletal disorders (MSD), a leading cause of workplace injury. MSDs make up the largest category of workplace injuries and cost employers over $300 billion annually in direct and indirect costs.

While contact stress is often not considered to be as dangerous as certain other ergonomic hazards, it can impair worker productivity and precision and can disable workers for life. Avoid this issue by identifying common risk factors at your workplace and educating your employees to recognize and prevent contact stress.

Contact Stress Defined

There are two distinct types of contact stress: internal and external. Internal contact stress happens when muscles, nerves, tendons, or other soft tissue rubs, or presses, against bone or tendons in a way that causes the tissue to bruise or over-extend. External contact stress occurs when a part of the body comes into contact with a hard surface such as a desk or machinery.

Contact stress can become more intense if the force is excessive or if the contact surface is relatively small relevant to the body part that comes into contact with it. The more pressure applied, the more serious the injury or damage is likely to be. Fat and muscle can protect the body from contact stress, so the parts of the body most at risk are those with the least amount of protective tissue.

As nerves or blood vessels are pinched or bruised, a person with a contact stress injury may feel pain or numbness. He or she may also suffer impaired motion and stiffness. These are early warning signs that employees should be told to look out for.

Causes of Contact Stress

There are several common causes of contact stress in the workplace. These include:

• Tasks involving handling objects with sharp or uneven edges
• Tools or equipment with handles or triggers that have sharp grooves, edges or hard grips
• Movements or activities that require contact with hard surfaces
• Controls that require the use of the palm to operate
• Tool handles that are too short or hard that press into the base of the hand
• Kneeling, resting or leaning on a sharp or hard surface
• Forceful exertion with unprotected parts of the body
• Walking or kneeling on hard surfaces
• Machinery or office setups that require maintenance of an awkward posture

In addition to engaging your employees in identifying the causes of contact stress, provide information on the additional risk factors that can affect the severity of a contact stress injury.

Contact stress causes should be assessed in conjunction with these additional risk factors, which include magnitude, duration, vibration and cold.

• Magnitude refers to the amount of pressure applied to the part of the body. It includes both the force of the pressure and the speed at which it is applied. The more pressure applied, the more the chance of injury increases.
• Duration is the amount of time that a worker is exposed to contact stress. The frequency of exposure is important, but so is the total amount of exposure over time. Many of the most severe contact stress injuries are cumulative in nature and develop following repeated exposure.
• Vibration and cold, alongside other ergonomic hazards, can also be mitigating factors and increase the dangers for workers.

Areas Prone To Contact Stress Injuries

Several key areas of the body are more prone to contact stress injuries than others. This is mostly because these are also the body parts your workers are most likely to use in the kinds of activities that tend to cause this stress.

Hands

The fat pads that cover the palms of the hands work to protect them from injury when you grip items or use tools. Pressure applied to a different part of the hand, such as the side of fingers where there is little protection, however, can cause injury as the digital nerves or blood supply are compressed. An example of this might be prolonged use of scissors or small knives. The use of tools, such as pliers, with hard grips can also cause this type of damage.

The Ulnar Nerve

The ulnar nerve runs the length of the hand and arm from the tip of the ring and baby fingers to beyond the elbow. As it runs close to the surface at both the wrist and the inside of the elbow, it puts these two areas at risk. Leaning on your elbows or wrists for long periods of time, as well as prolonged flexion of the elbow, can cause permanent damage to the nerve. Compression of this ulnar nerve can also lead to tingling, persistent pain, a weakened grip and even muscle atrophy.

Feet and Knees

Continuous walking on a hard surface, such as those found in many warehouses and manufacturing plants, can damage both feet and knees. Kneeling on hard surfaces or against sharp edges can also cause damage if it occurs over a long period.

Although employers must minimize or eliminate the risk of contact stress, your employees can help. Educate them about the risk and about what they can do to mitigate it.

Tips To Reduce The Risk of Contact Stress Injuries

Here are a few additional tips you can implement to control the risks to you and your employees:

• Encourage workers to use knee pads and padded work gloves
• Pad or round out the edges of tools, objects and workstations
• Buy and use tools with long handles and spring-assists
• Remind everyone to distribute pressure evenly and avoid kneeling or standing on hard surfaces
• Avoid the use of the hand or knee to strike objects
• Rotate jobs and take rest breaks
• Use team lifts or mechanical material handling tools wherever possible