Ergo Flooring

A COMFORTABLE STAND

BY WENDY DUNK

"...muscle fatigue can build up into an intolerable pain if you try to stand in one position for too long."

Almost everyone has experienced sore and aching feet, knees, hips or back after a day of standing or walking on a hard surface. To a certain extent, the discomfort can be blamed on our physical condition, our shoes, and on "just not being used to it".

Standing and walking are, however, essential components in a wide variety of jobs, and even in well designed jobs the standing and walking activities can lead to fatigue and discomfort when they are performed on hard, unyielding floor surfaces.

Studies have found that workers report improved comfort and decreased perceptions of fatigue when they work, stand or walk on more elastic surfaces such as wood, cork, rubber or carpet (compared to hard surfaces such as concrete and tile).

For this reason, "anti-fatigue mats" are in widespread use in many industries. Manufacturers claim that they are not only more comfortable than hard floor surfaces, but that they actually reduce muscle fatigue and improve circulation in the legs.

SHOCK VALUE

Each step we take transfers our entire body weight to one foot, then the other, over and over again, many thousands of times each day. (A recent study of hospital nurses, for example, found that they can walk an average of nearly 10 miles on a single shift.) Depending on how vigorously we walk, the actual dynamic force with each step may be far greater than our static body weight -- our entire body weight is in motion, and is snapped to a complete stop as each foot hits the ground. The pounding our heels get with each step generates a shock wave of forces that travel up the leg, through the hip and pelvis to the back.

Walking on a hard surface increases the magnitude of the shock wave that travels up the leg with each step, since hitting the hard surface stops the foot instantly. And most of the energy is directed back up the leg. On a softer surface, the foot hitting the floor depresses the floor surface very slightly and thus generates less of a shock wave.

When joints are exposed to these increased stresses over a long period of time, the result can be permanent joint damage.

STANDING HURTS

Standing on any surfaces for long periods of time -- especially if it's in one position -- can give rise to a whole other set of problems, and for a very different set of reasons. The way our muscles work when we stand is somewhat different from the way they work when we walk, and this contributes to muscle fatigue and discomfort.

During walking, some muscles are working dynamically to change our position. While we are standing still, muscles are working statically to hold us in the required posture. When muscles are working statically they are contracting continuously, compressing the blood vessels, whereas muscles that are working dynamically compress and relax cyclically, acting like a pump in the blood system.

When a muscle is performing heavy static work, the constant compression prevents the blood from flowing through the muscle properly, and it quickly becomes fatigued. Discomfort from muscle fatigue can build up into an intolerable pain if you try to stand in one position for too long. In the long term, the lasting effects of doing so repeatedly can be damage to the joints, ligaments, and tendons, including arthritis due to mechanical stress, tendonitis and degeneration of the joints.

During standing, blood pooling occurs in the feet and legs because there are no dynamic contractions of the leg muscles to assist with pumping the blood against gravity back to the heart. This tends to accelerate muscle fatigue and, over time, the blood pooling can also lead to chronic swelling of the feet and legs and varicose veins.

Because our joints are designed to move, periods of prolonged immobility place a greater stress on them. This increased joint strain can lead to discomfort in the short term, and possibly to degenerative damage to the joints if the stresses are repeated over a long period of time.

The feet themselves are also a major source of discomfort among workers who stand or walk for extended periods. Foot complaints among these employees include common disorders such as calluses, blisters, corns, and bunions. These complaints, while often painful, are rarely considered dangerous. Over the long term, however, the affects of continuous standing and walking on the feet can include more serious conditions such as a malformation of toes and fallen arches, which in turn can lead to more serious problems.

JOB DESIGN

One of the most important steps toward reducing discomfort due to standing and walking is to design jobs to reduce the employee's exposure to these activities. Expanding jobs to include a variety of activities (not just standing in one place); providing an opportunity to sit at regular intervals; or providing a footrest to allow employees to change posture or shift their body weight from one leg to another are all examples of how this can be accomplished.

One strategy that is widely used consists of using footwear specially designed to absorb shock and reduce fatigue. In situations in which the employee covers a large area, or where the environment cannot be controlled, (such as for nurses or security guards) shock-absorbing insoles are often the preferred approach.

There are limitations to the use of insoles however. They can interfere with moisture regulation in the shoe, causing increased heat and moisture, which can contribute to problems such as fungal infections. They also need to be replaced frequently as the material will deteriorate through use, losing the shock absorbing properties. The use of the insoles is also difficult to enforce, as they are not readily visible to supervisors or managers.

Another possible strategy, that might be used in addition to optimizing the job design, is to change the floor surface that workers stand and walk on.

Changing or covering the entire floor surface is often not feasible in many work environments, and many employers provide employees with mats designed to make standing and walking less painful.

Generally, however, it is a combination of work organization and changes to the floor surface that will provide the greatest reduction in discomfort and injury risk.

CONFLICTING THEORIES

Several conflicting theories exist regarding why anti-fatigue mats may reduce fatigue and improve circulation. One suggests that soft surfaces cause the body to sway slightly, which causes the leg and back muscles to contract and relax in a cyclic pattern in an attempt to maintain balance. This decreases the static work in the muscles, and helps to pump blood out of the legs, increasing circulation and reducing the onset of muscular fatigue. Another theory is that, when standing on a soft surface, body weight is distributed more evenly over a larger area of the foot (rather than just the heel and ball of the foot), resulting in improved foot comfort. When the feet are more comfortable, there is a decreased tendency to move around, and this reduction in movement decreases the amount of required muscular work.

There is a lack of agreement among researchers regarding whether or not anti-fatigue mats actually do decrease muscle fatigue or improve circulation. Some studies report no differences in leg and foot swelling caused by blood pooling, while others have found that muscular work in the legs is reduced, and still others report that a reduction in muscular work is found only in the back muscles. However, there is a great deal of evidence that suggests that perceived comfort is improved through the use of these mats. The benefits of improved perceptions of comfort and reduced fatigue on employee morale and productivity should not be discounted.

When selecting mats for your environment, there are a number of things to consider. To reduce tripping hazards, mats should have smooth joins between pieces, and beveled edges. They should have high-contrast colours on the edges. If the environment is wet, select mats that have holes so that water passes through the mat, rather than collecting on top. The degree to which workers report improved comfort and decreased fatigue varies significantly between different types of floor surfaces and mats. Comfort level seems to depend on both the hardness of the surface and on how far the feet sink into it. Hard, anti-slip mats provide little additional comfort, whereas firm rubber promotes increased comfort. Overly soft mats such as foam rubber can actually increase fatigue, as the feet tend to sink in very slightly, increasing the work required to move the feet (consider the fatigue that occurs when walking in soft sand).

Once you have decided what features or properties are important in your workplace, ask various suppliers for samples of mats that meet your criteria. Allow a representative sample of workers to use the mats for an extended period (up to two weeks) and get feedback regarding their comfort levels at the end of their shifts and at the end of the trial period.

Compare their reports using different mat samples and choose the mat that provides the greatest subjective comfort for the largest number of workers. It is generally recognized that when workers are experiencing discomfort or fatigue, their behaviour and productivity at work will be affected. Foot, leg or back discomfort can increase absenteeism and decrease employee morale and productivity.

Regardless of whether mats actually reduce muscular fatigue or improve circulation however there is a great deal of anecdotal and research evidence that suggests that perceived comfort is improved through the use of these mats. The benefits of improved perceptions of comfort and reduced fatigue on employee morale and productivity should not be discounted, and in addition, mats can have other benefits. These include improved shoe traction, decreased breakage of parts or sensitive equipment, and a reduction of drafts and ambient noise levels. Some mats also have special properties such as static dissipation and chemical, electrical, and fire resistance.

Considering all of the potential problems associated with standing and walking, it's not surprising that many companies are taking steps to improve employee comfort and reduce the potential for long term health affects related to these activities. 

Wendy Dunk is an Ergonomics Consultant with Human Factors North Inc. based in Toronto, Ontario.

Top

Back to contents