Are you sitting comfortably?

People are spending longer and longer periods of their days sitting down, at work in front of their computer screens; at home in front of their televisions or in front of their home computers surfing the net; or in their cars driving to their work or homes. Hence, there is an urgent need to look at domestic seating and design new furniture based on sound ergonomics.

Introduction

People are spending longer and longer periods of their days sitting down, at work in front of their computer screens; at home in front of their televisions or in front of their home computers surfing the net; or in their cars driving to their work or homes. Hence, there is an urgent need to look at domestic seating and design new furniture based on sound ergonomics. The furniture we currently use in our houses is not ergonomically ‘correct’, is not suitable for what we want to use them for and they are dimensionally wrong for the majority of people. If the health and safety regulations for the work place were to be applied to the home environments, some of the furniture we use in our homes could possibly be classified as ‘illegal’. Why do we have to wait for regulations to improve the ergonomics of domestic furniture?

By the age of 40 or younger we expect to experience some kind of back pain. This can only get worse as we spend a greater proportion of our days sitting on furniture which does not fit us, does not support our body adequately, is too soft and is not designed for the purpose we actually want to use it for. Because badly designed domestic furniture does not kill people like the fumes from burning of the wrong type of foams, people accept the lack of ergonomic considerations and ill effects of badly designed furniture on their backs. However, in recent years, there has been a few litigation cases where the public tried to sue the manufacturers or the retailers for the back pain they suffered which they argued was due to the ‘unergonomic’ nature of the domestic furniture they had been sold. With the introduction of recent ‘General Product Safety Regulations, 1994’ manufacturers and retailers could be held responsible for providing furniture which could adversely affect people’s backs.

What is so bad about the majority of currently available domestic furniture?

One of the major problems is that the dimensions of furniture does not match the sizes of people who use it.

With the possible exception of dining and bedroom chairs, easy chairs especially sofas, are much too deep for the majority of the adult population. This forces people either to sit at the front edge of the seat and slouch (lumbar unsupported, spine in C-shape instead of the natural S-shape) or sit with their feet sticking out. To remedy the situation people will buy cushions to stuff behind their backs or pouffes to support their lower legs and feet. The ergonomic solution for this would be to design a seat depth which is suitable for short users, or to offer different seat depths.

The seat heights are often too low, which makes getting up difficult, especially for the elderly. If the seat is too high, sitters’ feet cannot touch the floor and the blood flow to the lower leg and the feet is restricted, causing discomfort and sometimes the feeling of pins and needles. Short people will compensate for this defect by sitting on their legs on the seat which becomes uncomfortable after a while, hence forcing them to ‘fidget’ in their seats; or they will use a pouffe to rest their legs on. Whilst young people can feel comfortable in a low seat with the seat base sloping downwards at the back, elderly people prefer a seat height corresponding to their popliteal height (heel to back of knee) and with a non-sloping seat base. So, designers must decide on their intended user population and use the appropriate seat height and slope.

The angle of the backrest and the height of the backrest is not suitable for the purpose the seats are used for. Most people will use their easy chairs and sofas to relax in, possibly to read or watch television. This would require an angle of approximately 115 degrees between the seat and the back rest, so that the sitter is in a reclined posture. This angle is present in currently available furniture but the problem with this furniture is the back rest not being sufficiently high. When one is in a reclined posture the head must be supported, otherwise the neck and shoulder muscles will have to work hard to keep the head from falling backwards. This at best causes fatigue and at worst forces the sitter to slouch in order to rest their head at the top of the back rest. This slouch has the same ill effects on the spine as the slouch due to the seat being too deep. The ergonomics solution would be to design high back chairs with a neck cushion, the position of which can be adjusted to suit the user.

Seats are too soft, so when we sit in them we sink into the seat. Initially, this may feel comfortable but soon one will feel the lack of support for the ischial tuberosities (bony parts of our pelvis on which we sit). A good seat should provide a firm support for the buttocks. In fact the density of the foam at the back of the seat should be greater than the foam at the front of the seat. Seats which are soft when they are new, become deformed very quickly and provide too little support for the buttocks.

Many people purchase sofas with the intention of lying on them. Some sofa arm designs cause to bend and harm their necks.

Contact: Levent Çaglar
E-mail: info@fira.co.uk