ergonomics

Force. Impact. Reaction.

Perception: better shoes are the only For every action, there is an equalanswer to tired feetand opposite reaction

Newton's Third Law of Motion famously states: When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body. By the simple act of walking, we subject ourselves to significant forces every day just by putting foot to floor. Fatigue, lower back & leg injuries and plantar fasciitis are just some of the conditions caused, in whole or part, by the forces experienced by the human body through the foot.

"Underfoot comfort" is often discussed, but has never been objectively measured. Until now. Numerous studies going back decades have focused almost entirely on the measurement of subjective fatigue due to prolonged standing on different types of floors and mats. In close cooperation with The University of Pittsburgh Bioengineering Department, we have developed a test method designed to measure the direct impact of walking on the human body. As part of an extensive graduate study on human fatigue attributed to prolonged standing or walking on different flooring surfaces, this test method measures the reduction of Ground Reaction Force (GRF) of floor covering materials. The test utilizes state-of-the-art pressure mapping equipment molded into a test shoe that is free of cushioning and allows the measurement of the return force imparted on the foot, through the floor covering, without the variable of footwear.

The GRF being measured through the foot during one complete cycle of walking for both the left and right foot for two different floor coverings. For reference, the first spike represents the initial heel strike with the floor.

Figure 2

Figure 1A representative mapping of the GRF being applied to the foot as detected by the pressure sensors.

Ground Reaction Force and impact on the human body The data

The results

The average GRF as measured onthe different floor coverings over 50 cycles.

Figure 3

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220

The mileage that staff, students, patients and visitors can walk on any given day has significantly increased over the years. Campuses grow and facilities expand, so providing spaces that support good ergonomics is an ever growing challenge decision makers face as they look to recruit and retain staff, as well as ensure the safety of patients and students. Musculoskeletal disorders account for one-third of all occupational injuries and illnesses reported by employers, constituting the largest job related injury and illness problem in the United States. Indirect costs, such as lost productivity, retraining and sick or administrative time, can be at least 4 to 10 times more than the direct costs.

We selected its four most popular floor coverings and comparatively tested them under identical conditions versus three other very common resilient floor coverings: 2.5mm linoleum, 2mm sheet vinyl and 2mm 'wood-look' sheet vinyl. Each floor covering was tested for 50 cycles and the average GRF measured at the foot was calculated for each. Average GRF is calculated over one entire cycle of walking, from the time the heel first hits the floor through to when the foot is lifted from the foor.

It is challenging to definitively quantify the impact walking, or just simply standing, on certain surfaces can directly have on the human body. However, by utilizing the best possible data and evidence, informed decision makers can select those products that help create the most ergonomically safe environment for their customers and staff.

Note: Relative reduction in ground reaction force will vary depending upon the mass of the person and the walking gait.