ARTICLE: The Pains of Standing

Why is it less tiring to stand eight hours on an anti-fatigue mat than eight hours on a hard surface? The secret is how the mats work.

Bill Roberts had worked in a small factory in Lansing , Mich., for 15 years, and in all that time he had assumed aching legs and sore feet at the end of the day were unavoidable consequences of his profession. Standing on a hard concrete factory floor for eight hours every day was bound to tire him out, and there wasn't much he could do about it. Aspirin before he went to bed at night and maybe an ice pack after an especially long day tended to be the extent of Roberts' treatment.

Then he began to notice that when he got out of bed in the morning, he was greeted by pain in his heels. Roberts didn't think much about it at first, but as time passed the pain grew worse until it was like having knives stabbed in his heels when he took his first step in the morning. After he moved around for a while, the sharpness of the pain wore off into a dull ache. But every morning the pain got worse and worse, and his heels began to look bruised and somewhat swollen.

When he finally made it to his doctor's office, it took not more than a short question-and-answer session for the physician to diagnose his ailment. "Plantar fasciitis," Bill Roberts' doctor told him.

Also called heel spur syndrome, plantar fasciitis is the heel bone's reaction to repeated stress or weight bearing. It can be caused by extensive running and exercise, but it is also the result of standing for long periods of time on hard surfaces, such as tile or concrete. Ivory Larry, director of the foot care clinic at the University of Washington Medical Center's Bone and Joint Center , likens plantar fasciitis to other "overuse injuries," such as shin splints and carpal tunnel syndrome.

Constant stress and pressure cause the ligament on the bottom of the foot, know as the plantar fascia, to become inflamed. The plantar fascia forms the foot's arch by working like a rubber band between the heel and ball of the foot. Plantar fasciitis happens more often in older people because their plantar fascias have become more like ropes than rubber bands, and the shock-absorbing pads of fat in the heels have worn down over time. People who are overweight also are at higher risk because their body weight puts additional stress on their feet.

Often, because of tension in the ligament, a bony spur will develop in the heel of the foot. The spur, however, is not the source of pain. The inflammation of the ligament causes the searing pain along the bottom of the foot, which some have compared with being pierced by a pin or knife. The pain is often most noticeable first thing in the morning, and its sharpness usually becomes a dull ache after standing or walking for a while.

Other Problems Associated With Standing

Anyone who stands all day at work knows how tiring it is. Standing for seven or eight hours isn't hard on just the feet, but the entire body, from the heels to the leg muscles to the spine. To learn just how exhausting it can be, ask members of the meatpacking industry, assembly line workers, cashiers, or machinists.

Standing hurts because it is basically a battle against gravity. When standing, your body is continually pulled by the force of gravity; to maintain your position, your body must supply counteracting forces to maintain an equilibrium. This means your muscles are constantly tensed, which results in a static stress situation. Dan MacLeod, director of ergonomics at Clayton Environmental Consultants, put it this way: "The human does not tolerate well standing on a hard surface. It's fatiguing and hard on the feet and spinal column."

Unfortunately, some jobs simply cannot be accomplished sitting down. Stand-up work is necessary when there is no room for a stool, when the weight of objects being handled is more than 4.5 kilograms, or if the worker must constantly be reaching high, low, or far.

Standing for long periods on hard surfaces can lead to several problems. First, standing causes muscles to constrict, which leads to reduced blood flow. This makes muscles and joints hurt, and it causes blood to stagnate, which can cause varicose veins. In addition, long-term standing causes pronation, or extensive flattening of the foot. While this can be simply tiring and a bit painful, it can lead to plantar fasciitis and other serious conditions.

This is where anti-fatigue mats come in.

How Anti-Fatigue Mats Work

The premise behind anti-fatigue mats is deceptively simple. Logic suggests that standing on something soft would be more comfortable. But why would standing on a soft surface be less tiring than on a hard surface, if you're standing for the same length of time?

Here's why: Anti-fatigue mats are engineered to make the body naturally and imperceptibly sway, which encourages subtle movement by calf and leg muscles. This promotes blood flow and keeps the blood from stagnating in the veins, which causes workers to feel fatigued. However, there is a fine line between making a mat either too hard and not causing enough muscle movement, or too springy so the workers use too much energy keeping their balance, thus defeating the mat's entire purpose.

There have been relatively few studies conducted that back up the effectiveness of anti-fatigue mats. One of the problems with such studies is that they are generally subjective, because they rely heavily on questionnaires asking about "perceived fatigue." Researchers run into problems defining just what fatigue is. What is fatiguing to one person might not be fatiguing to the next.

This was the case with one of the best-known studies, which was conducted by Mark Redfern at the University of Michigan in 1987. The study involved 14 workers who stood all day at their jobs at the Ford Chesterfield Trim Plant. They were asked to fill out a questionnaire at the beginning and end of their eight-hour shifts, evaluating their body's overall tiredness as well as fatigue in specific areas of their bodies. The study evaluated nine flooring material conditions that varied in thickness and stiffness, ranging from a concrete floor to a 3/8"-thick anti-fatigue mat.

The results showed the mats had a significant effect on workers' perceived fatigue. The 3/8" anti-fatigue mat had the lowest rating for overall tiredness, which was 50 percent lower than the rating for the concrete floor. Proving that a surface can be too soft, however, the softest mat had one of the highest tiredness ratings. The study also found that the workers' feet had the highest discomfort rating after eight hours of standing. This comes as little surprise, considering that each foot contains 26 bones, 33 joints, 107 ligaments, and 19 muscles, all of which are constantly supporting our body weight.

For more objective testing, some researchers have turned to surface electromyography (EMG), but even that has its problems. One study conducted by the Ergonomics Department at Loughborough University in Loughborough , England , used a pressure plate to analyze standing patterns. Using six subjects standing for two hours at a time, the study found that energy used in calf muscles was conserved by 50 percent when standing on anti-fatigue mats. However, said Steve McCaw, director of the biomechanics lab at Illinois State University , "A problem inherent to the use of EMG is the large variability evident in activity levels across individuals. The variability is present even when muscle activity during a fixed task is used as a normalization factor."

What About Insoles?

Some companies ask why anti-fatigue matting should be limited to mats. "Our premise is, why limit yourself to one certain area when you can have anti-fatigue matting wherever you go, with insoles?" said Brian Gordon, product development engineer at Sorbothane, based in Kent , Ohio . "We haven't found any benefits to having anti-fatigue mats versus using insoles. Actually, we think insoles are better because having an insole is like having a mobile mat."

This claim is supported by several studies, including the Michigan study conducted by Redfern. One of the nine flooring materials evaluated was a "viscoelastic shoe insert," which scored among the three highest in comfort ratings. Another study, by Jeffrey R. Basford and Martha A. Smith of the Mayo Clinic in Rochester , Minn. , concluded that "viscoelastic insoles can effectively improve comfort and reduce back, leg and foot pain in individuals who must stand throughout the day."

*James M. Kendrick is the editor of Workplace Ergonomics News and Environmental Health and Safety News for Stevens Publishing Corp., which publishes Occupational Health & Safety.

(Reprinted with permission of 1105 Media Inc., publisher of Occupational Health & Safety)