Background

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Introduction

Seating Discomfort

Factors to Consider when Designing a seat

Many studies have been done regarding the topic of ergonomics in the office, on how bad posture can create health problems. But people who drive for a living are also at risk. There is a misconception that sitting all day on a job makes that an easy job. Working for prolonged periods of time in a single fixed posture can lead to muscular problems. Millions of people who earn their living while sitting endure excessive pain, stress and strain. Some people feel it, but most get used to it.

In 2003, Calgary Transit had a fleet of 774 buses in service. Imagine 700 bus drivers driving for 8 hours a day, 365 days a year. For one such bus driver, that is 2920 hours of driving a year. What about truckers, mailmen and thousands of other people who drive for a living? Studies show that lower back injuries often occur in jobs like these.

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Seating Discomfort

We sit on:

• The two bony prominences called the Ischial tuberosities

• The thighs

• The fat and muscles surrounding the bony structures

When we sit:

• The skin begins to react to gravity

• The fat and muscles under the Ischia slowly move out.

• The skin under the Ischia becomes thinner, this is called "core down"

• The longer the person remains seated, the more pronounced this condition becomes

Physiological changes while seated

• Ischial brusae thicken to provide a cushion below the bone and as a result of the tissue damage caused by shear force, prostaglandin E2 is released, first locally and then systematically

• This is a chemical which contributes to depression, fatigue and sluggish reflexes

• Since pressure inhibits blood flow, the tissue immediately around the blood vessels thickens to help keep them open

• Lactic acid concentrates in the muscles (no oxygen)

• Water builds up in the subcutaneous tissues (under the skin)

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Factors to Consider when designing a seat:

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