Chair

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Typical Western wooden chair

A chair is a piece of furniture for sitting, consisting of a seat, a back, and sometimes arm rests, commonly for use by one person. Chairs also often have legs to support the seat raised above the floor. Without back and arm rests it is called a stool. A chair for more than one person is a couch, sofa, settee, loveseat (two-seater without arm rest in between) or bench. A separate footrest for a chair is known as an ottoman, hassock or poof. A chair mounted in a vehicle or in a theatre is simply called a seat. Chairs as furniture are typically not attached to the floor and so can be moved.

The back often does not extend all the way to the seat to allow for ventilation. Likewise, the back and sometimes the seat are made of porous materials or have holes drilled in them for decoration and ventilation.

The back may extend above the height of the head. There may be separate headrests. Headrests for seats in vehicles are important for preventing whiplash injuries to the neck when the vehicle is involved in a rear-end collision.

See history of the chair for an extended look at chairs from antiquity to the modern day.

Design and ergonomics

This unusual rocking chair is made of rough wood to give it an old-fashioned look.

Chair design considers intended usage, ergonomics (how comfortable it is for the occupant), as well as non-ergonomic functional requirements such as size, stackability, foldability, weight, durability, stain resistance and artistic design. Intended usage determines the desired seating position. "Task chairs", or any chair intended for people to work at a desk or table, including dining chairs, can only recline very slightly; otherwise the occupant is too far away from the desk or table. Dental chairs are necessarily reclined. Easy chairs for watching television or movies are somewhere in between depending on the height of the screen.

Ergonomic designs distributes the weight of the occupant to various parts of the body. A seat that is higher results in dangling feet and increased pressure on the underside of the knees ("popliteal fold"). It may also result in no weight on the feet which means more weight elsewhere. A lower seat may shift too much weight to the "seat bones" ("ischial tuberosities").

A reclining seat and back will shift weight to the occupant's back. This may be more comfortable for some in reducing weight on the seat area, but may be problematic for others who have bad backs. In general, if the occupant is suppose to sit for a long time, weight needs to be taken off the seat area and thus "easy" chairs intended for long periods of sitting are generally at least slightly reclined. However, reclining may not be suitable for chairs intended for work or eating at table.

The back of the chair will support some of the weight of the occupant, reducing the weight on other parts of the body. In general, backrests come in three heights: Lower back backrests support only the lumbar region. Shoulder height backrests support the entire back and shoulders. Headrests support the head as well and are important in vehicles for preventing "whiplash" neck injuries in rear-end collisions where the head is jerked back suddenly. Reclining chairs typically have at least shoulder height backrests to shift weight to the shoulders instead of just the lower back.

Some chairs have foot rests. A stool or other simple chair may have a simple straight or curved bar near the bottom for the sitter to place his/her feet on.

A kneeling chair adds an additional body part, the knees, to support the weight of the body. A sit-stand chair distributes most of the weight of the occupant to the feet.

Many chairs are padded or have cushions. Padding can be on the seat of the chair only, on the seat and back, or also on any arm rests and/or foot rest the chair may have. Padding will not shift the weight to different parts of the body (unless the chair is so soft that the shape is altered). However, padding does distribute the weight by increasing the area of contact between the chair and the body. A hard wood chair feels hard because the contact point between the occupant and the chair is small. The same body weight over a smaller area means greater pressure on that area. Spreading the area reduces the pressure at any given point. In lieu of padding, flexible materials, such as wicker, may be used instead with similar effects of distributing the weight. Since most of the body weight is supported in the back of the seat, padding there should be firmer than the front of the seat which only has the weight of the legs to support. Chairs that have padding that is the same density front and back will feel soft in the back area and hard to the underside of the knees.

There may be cases where padding is not desirable. For example, in hot climates, padding with fabric or plastic covers is often uncomfortable against the skin. Where padding is not desirable, contouring may be used instead. A contoured seat pan attempts to distribute weight without padding. By matching the shape of the occupant's buttocks, weight is distributed and pressure at any given point is reduced.

Actual chair dimensions are determined by measurements of the human body or anthropometric measurements. Individuals may be measured for a custom chair. Anthropometric statistics may be gathered for mass produced chairs. The two most relevant anthropometric measurement for chair design is the popliteal height and buttock popliteal length.

For someone seated, the popliteal height is the distance from the underside of the foot to the underside of the thigh at the knees. It is sometimes called the "stool height". (The term "sitting height" is reserved for the height to the top of the head when seated.) For American men, the median popliteal height is 16.3 inches and for American women it is 15.0 inches[1]. The popliteal height, after adjusting for heels, clothing and other issues is used to determine the height of the chair seat. Mass produced chairs are typically 17 inches high.

For someone seated, the buttock popliteal length is the horizontal distance from the back most part of the buttocks to the back of the lower leg. This anthropometric measurement is used to determine the seat depth. Mass produced chairs are typically 38-43 cm deep.

Additional anthropometric measurements may be relevant to designing a chair. Hip breadth is used for chair width and armrest width. Elbow rest height is used to determine the height of the armrests. The buttock-knee length is used to determine "leg room" between rows of chairs. "Seat pitch" is the distance between rows of seats. In some airplanes and stadiums the seat pitch is so small that there is sometimes there is no leg room for the average person.

For adjustable chairs, the aforementioned principles are applied in adjusting the chair to the individual occupant.

Arm rests

Traditional Japanese chair with zabuton and separate armrest Bus shelter with seats with arm rests in between

A chair may or may not have armrests. If so, armrests will support part of the body weight through the arms if the arms are resting on the armrests. Armrests further have the function of making entry and exit from the chair easier (but from the side it becomes more difficult). Armrests should support the forearm and not the sensitive elbow area. Hence in some chair designs, the armrest is not continuous to the chair back, but is missing in the elbow area.

A couch, bench, or other arrangement of seats next to each other may have arm rest at the sides and/or arm rests in between. The latter may be provided for comfort, but also for privacy e.g. in public transport and other public places, and to prevent lying on the bench or coach. Arm rests prevent or complicate both desired and undesired proximity. A loveseat in particular, has no arm rest in between.

See also seats in movie theaters, and pictures of benches with and without arm rests.

Chair seats

A bench is long enough for several people to sit on

Chair seats vary widely in construction and may or may not match construction of the chair's back. Some systems include: Solid center seats where a solid material forms the chair seat.

  • Solid wood, may or may not be shaped to human contours.
  • Wood slats, often seen on outdoor chairs
  • Padded leather, generally a flat wood base covered in padding and contained in soft leather
  • Stuffed fabric, similar to padded leather
  • Metal seats of solid or open design
  • Molded plastic
  • Stone, often marble

Open center seats where a soft material is attached to the tops of chair legs or between stretchers to form the seat.

  • Wicker, woven to provide a surface with give to it
  • Leather, may be tooled with a design
  • Fabric, simple covering without support
  • Tape, wide fabric tape woven into seat, seen in lawn chairs and some old chairs
  • Caning, woven from rush, reed, rawhide, heavy paper, strong grasses, cattails to form the seat, often in elaborate patterns
  • Splint, ash, oak or hickory strips are woven
  • Metal, Metal mesh or wire woven to form seat

Standards and specifications

Design considerations for chairs have been codified into standards. ISO 9241-5:1988[2], "Ergonomic requirements for office work with visual display terminals (VDTs) -- Part 5: Workstation layout and postural requirements " is the most common one for modern chair design.

There are multiple specific standards for different types of chairs. Dental chairs are specified by ISO 6875. Bean bag chairs are specified by ANSI standard ASTM F1912-98[3]. ISO 7174 specifies stability of rocking and tilting chairs. ASTM F1858-98 specifies lawn chairs. ASTM E1822-02b defines the combustibility of chairs when they are stacked.

The Business and Institutional Furniture Manufacturer's Association (BIFMA) defines BIFMA X5.1 for testing of commercial-grade chairs. It specifies things like[4]:

  • chair backstrength of 150 pounds (68 kg)
  • chair stability if weight is transferred completely to the front or back legs
  • leg strength of 75 pounds (34 kg) applied one inch (25 mm) from the bottom of the leg
  • seat strength of 225 pounds (102 kg) dropped from six inches (150 mm) above the seat
  • seat cycle strength of 100,000 repetitions of 125 pounds (57 kg) dropped from 2 inches (50 mm) above the seat

The specification further defines heavier "proof" loads that chairs must withstand. Under these higher loads, the chair may be damaged, but it must not fail catastrophically.

Large institutions that make bulk purchases will reference these standards within their own even more detailed criteria for purchase [5]. Governments will often issue standards for purchases by government agencies (e.g. Canada's Canadian General Standards Board CAN/CGSB 44.15M [6] on "Straight Stacking Chair, Steel").

Accessories

In place of a built-in footrest, some chairs come with a matching ottoman. An ottoman is a short stool to be used as a footrest but can sometimes be used as a stool. If matched to a glider, the ottoman may be mounted on swing arms so that the ottoman rocks back and forth with the main glider.

A chair cover is a temporary fabric cover for a side chair. They are typically rented for formal events such as wedding receptions to increase the attractiveness of the chairs and decor. The chair covers may come with decorative chair ties, a ribbon to be tied as a bow behind the chair. Covers for sofas and couches are also available for homes with small children and pets. In the second half of 20th century, some people used custom clear plastic covers for expensive sofas and chairs to protect them.

Chair pads are cushions for chairs. Some are decorative. In cars, they may be used to increase the height of the driver. Orthopedic backrests provide support for the back. Obus Forme is a major brand in this category and helped develop this market niche. Car seats sometimes have built-in and adjustable lumbar supports.

Chair mats are plastic mats meant to cover carpet. This allows chairs on wheels to roll easily over the carpet and it protects the carpet. They come in various shapes, some specifically sized to fit partially under a desk.

Remote control bags can be draped over the arm of easy chairs or sofas and used to hold remote controls. They are counter-weighted so as to not slide off the arms under the weight of the remote control.

English phrases relating to chairs

A movie or a story is said to keep you on the edge of your chair, if it is suspenseful and engaging.

If you nearly fell off your chair, it was because you were very surprised.

Activities that are likely to be made insignificant or undone by some future event are said to be like rearranging the deckchairs on the Titanic.

When English-speaking philosophers talk about the material world as opposed to ideas, their phrase is tables and chairs.


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When English-speaking philosophers talk about the material world as opposed to ideas, their phrase is tables and chairs. This article incorporates text from the 1911 Encyclopædia Britannica, a publication in the public domain.. Activities that are likely to be made insignificant or undone by some future event are said to be like rearranging the deckchairs on the Titanic. Morales asserts that "coca no es cocaína"--the coca leaf is not cocaine. If you nearly fell off your chair, it was because you were very surprised. In December 2005, Evo Morales, a former coca growers union leader, was elected President of Bolivia and promised to legalize the cultivation and traditional use of coca. A movie or a story is said to keep you on the edge of your chair, if it is suspenseful and engaging. This provision is designed to accommodate Coca-Cola and other producers of coca products.

They are counter-weighted so as to not slide off the arms under the weight of the remote control. Article 27 states that "The Parties may permit the use of coca leaves for the preparation of a flavouring agent, which shall not contain any alkaloids, and, to the extent necessary for such use, may permit the production, import, export, trade in and possession of such leaves". Remote control bags can be draped over the arm of easy chairs or sofas and used to hold remote controls. The Article 23 controls referred to in paragraph 1 are rules requiring opium-, coca-, and cannabis-cultivating nations to designate an agency to regulate said cultivation and take physical possession of the crops as soon as possible after harvest. They come in various shapes, some specifically sized to fit partially under a desk. Article 26 of the Single Convention on Narcotic Drugs states:. This allows chairs on wheels to roll easily over the carpet and it protects the carpet. [1] In Colombia, the Paeces, a Tierradentro (Cauca) indigenous community, started in December 2005 to produce a drink called "Coca Sek." The production method belong to the resguardos of Calderas (Inzá) and takes about 150 kg of coca per 3000 produced bottles.

Chair mats are plastic mats meant to cover carpet. The cocaine itself does not end up in the drink nowadays, however, and is generally sold to the pharmaceutical industry where it is used for various surgical procedures. Car seats sometimes have built-in and adjustable lumbar supports. The Coca-Cola Company buys 115 tons of coca leaf from Peru and 105 tons from Bolivia per year, which it uses as an ingredient in its Coca-Cola formula (famously a trade secret). Obus Forme is a major brand in this category and helped develop this market niche. Coca is used industrially in the cosmetics and food industries. Orthopedic backrests provide support for the back. Several pipes taken from Shakespeare's residence and dated to the seventeenth century have shown evidence of cocaine, which was first introduced to Europe in the 16th century.

In cars, they may be used to increase the height of the driver. showed traces of cocaine (and nicotine), and these studies have been used as evidence of pre-Columbian trans-oceanic contact. Some are decorative. to 395 A.D. Chair pads are cushions for chairs. Samples taken from nine Egyptian mummies that were dated from between 1070 B.C. In the second half of 20th century, some people used custom clear plastic covers for expensive sofas and chairs to protect them. Historical evidence points to a long history of coca export.

Covers for sofas and couches are also available for homes with small children and pets. Modern export of processed coca (as cocaine) to global markets is well documented, and coca leaves are exported for coca tea, flavoring (Coca-Cola), and for medical use. The chair covers may come with decorative chair ties, a ribbon to be tied as a bow behind the chair. Coca has a long history of export and use around the world. They are typically rented for formal events such as wedding receptions to increase the attractiveness of the chairs and decor. Commercially manufactured coca teas are also available in most stores and supermarkets, including upscale suburban supermarkets. A chair cover is a temporary fabric cover for a side chair. Bags of coca leaves are sold in local markets and by street vendors.

If matched to a glider, the ottoman may be mounted on swing arms so that the ottoman rocks back and forth with the main glider. It also serves as a powerful symbol of indigenous cultural and religious identity, amongst a diversity of indigenous nations throughout South America. An ottoman is a short stool to be used as a footrest but can sometimes be used as a stool. Even today, chewing coca leaves is a common sight in indigenous communities across the central Andean region, particularly in places like the mountains of Bolivia, where the cultivation and consumption of coca is as much a part of the national culture as wine is to France or beer is to Germany. In place of a built-in footrest, some chairs come with a matching ottoman. Doing so usually causes users to feel a tingling and numbing sensation in their mouths, similar to receiving Novocain during a dental procedure. Canada's Canadian General Standards Board CAN/CGSB 44.15M [6] on "Straight Stacking Chair, Steel"). The Spanish masticar is also frequently used.

Governments will often issue standards for purchases by government agencies (e.g. The activity of chewing coca is called chacchar or acullicar, borrowed from Quechua, or in Bolivia, picchar, derived from the Aymara language. Large institutions that make bulk purchases will reference these standards within their own even more detailed criteria for purchase [5]. This act of initiation is carefully supervised by the mama, a traditional leader. Under these higher loads, the chair may be damaged, but it must not fail catastrophically. When the boy is ready to be married, his mother will initiate him in the use of the coca. The specification further defines heavier "proof" loads that chairs must withstand. But it is the woman who gives man their manhood.

It specifies things like[4]:. It is important to stress that poporo is the symbol of manhood. The Business and Institutional Furniture Manufacturer's Association (BIFMA) defines BIFMA X5.1 for testing of commercial-grade chairs. Women are prohibited of using coca. ASTM E1822-02b defines the combustibility of chairs when they are stacked. For a man the poporo is a good companion which means "food" "woman", "memory" and "meditation". ASTM F1858-98 specifies lawn chairs. The movements of the stick in the poporo symbolize the sexual act.

ISO 7174 specifies stability of rocking and tilting chairs. It represents the womb and the stick is a phallic symbol. Bean bag chairs are specified by ANSI standard ASTM F1912-98[3]. The poporo is the mark of manhood, but it is a female's sexual symbol. Dental chairs are specified by ISO 6875. In the Sierra Nevadas de Santa Marta, on the Caribbean Coast of Colombia, coca is consumed by the Kogi, Arhuaco & Wiwa by using a special gadget called poporo. There are multiple specific standards for different types of chairs. Coca leaves are often read in a form of divination analogous to reading tea leaves in other cultures.

ISO 9241-5:1988[2], "Ergonomic requirements for office work with visual display terminals (VDTs) -- Part 5: Workstation layout and postural requirements " is the most common one for modern chair design. Coca leaves play a crucial part in offerings to the apus (mountains), Inti (the sun), or Pachamama (the earth). Design considerations for chairs have been codified into standards. It is believed by the miners of Cerro de Pasco to soften the veins of ore, if masticated (chewed) and thrown upon them (see also Cocomama). Open center seats where a soft material is attached to the tops of chair legs or between stretchers to form the seat. Coca is still held in veneration among the indigenous and mestizo peoples of Peru, Bolivia, Ecuador, Colombia and northern Argentina and Chile. Some systems include: Solid center seats where a solid material forms the chair seat. Coca was historically employed as an offering to the Sun, or to produce smoke at the great sacrifices; and the priests, it was believed, must chew it during the performance of religious ceremonies, otherwise the gods would not be propitiated.

Chair seats vary widely in construction and may or may not match construction of the chair's back. Coca was also a vital part of the religious cosmology of the Andean tribes in the pre-Inca period as well as throughout the Inca Empire (Tahuantinsuyu). See also seats in movie theaters, and pictures of benches with and without arm rests. In testament of the significance of coca to indigenous cultures, it is widely believed that the word "coca" most likely originally simply meant "plant," in other words, coca was not just a plant but the plant. A loveseat in particular, has no arm rest in between. Cocada can also be used as a measurement of time, meaning the amount of time it takes for a mouthful of coca to lose its flavor and activity. Arm rests prevent or complicate both desired and undesired proximity. The coca plant was so central to the worldview of the Yunga and Aymara tribes of South America that distance was often measured in units called "cocada", which signified the number of mouthfuls of coca that one would chew while walking from one point to another.

in public transport and other public places, and to prevent lying on the bench or coach. The perceived boost in energy and strength provided by the cocaine in coca leaves was also very functional in an area where oxygen is scarce and extensive walking is essential. The latter may be provided for comfort, but also for privacy e.g. It is rich in protein and vitamins, and it grows in regions where other food sources are scarce. A couch, bench, or other arrangement of seats next to each other may have arm rest at the sides and/or arm rests in between. The coca leaf contained many essential nutrients in addition to its more well-known mood-altering alkaloid. Hence in some chair designs, the armrest is not continuous to the chair back, but is missing in the elbow area. The practice of chewing coca was most likely originally a simple matter of survival.

Armrests should support the forearm and not the sensitive elbow area. In some places, baking soda is used under the name bico. Armrests further have the function of making entry and exit from the chair easier (but from the side it becomes more difficult). The most common base in the La Paz area of Bolivia is a product known as lejía dulce which is made from quinoa ashes mixed with anise and cane sugar, forming a soft black putty with a sweet and pleasing licorice flavor. If so, armrests will support part of the body weight through the arms if the arms are resting on the armrests. Many of these materials are salty in flavor, but there are variations. A chair may or may not have armrests. Other names for this basifying substance are llipta in Peru and lejía in Bolivia.

For adjustable chairs, the aforementioned principles are applied in adjusting the chair to the individual occupant. A tiny quantity of ilucta is chewed together with the coca leaves; it softens their astringent flavor and activates the alkaloids. In some airplanes and stadiums the seat pitch is so small that there is sometimes there is no leg room for the average person. They traditionally carried a woven pouch called a chuspa or huallqui in which they kept a day's supply of coca leaves, along with a small amount of ilucta or uipta, which is made from pulverized unslaked lime or from the ashes of the quinoa plant. "Seat pitch" is the distance between rows of seats. In the Andes, the indigenous peoples have been chewing the leaves of the coca plant for millennia. The buttock-knee length is used to determine "leg room" between rows of chairs. Some anesthetics such as Novocaine are derived from the coca plant.

Elbow rest height is used to determine the height of the armrests. When chewed, Coca acts as a stimulant to help ignore hunger sensations, thirst, and fatigue. Hip breadth is used for chair width and armrest width. Besides cocaine, the coca leaf contains a number of other alkaloids, including Methylecgonine cinnamate, Benzoylecgonine, Truxilline, Hydroxytropacocaine, Tropacocaine, Ecgonine, Cuscohygrine, Dihydrocuscohygrine, Nicotine and Hygrine. Additional anthropometric measurements may be relevant to designing a chair. The pharmacologically active ingredient of coca is the alkaloid cocaine which is found in the amount of about 0.2% in fresh leaves. Mass produced chairs are typically 38-43 cm deep. The green leaves (matu) are spread in thin layers on coarse woollen cloths and dried in the sun; they are then packed in sacks, which must be kept dry in order to preserve the quality of the leaves.

This anthropometric measurement is used to determine the seat depth. The first and most abundant harvest is in March, after the rains; the second is at the end of June, the third in October or November. For someone seated, the buttock popliteal length is the horizontal distance from the back most part of the buttocks to the back of the lower leg. They are considered ready for plucking when they break on being bent. Mass produced chairs are typically 17 inches high. The leaves are gathered from plants varying in age from one and a half to upwards of forty years. The popliteal height, after adjusting for heels, clothing and other issues is used to determine the height of the chair seat. The plants thrive best in hot, damp situations, such as the clearings of forests; but the leaves most preferred are obtained in drier localities, on the sides of hills.

(The term "sitting height" is reserved for the height to the top of the head when seated.) For American men, the median popliteal height is 16.3 inches and for American women it is 15.0 inches[1]. The seeds are sown in December and January in small plots (almacigas) sheltered from the sun, and the young plants when from 40-60 cm in height are placed in holes (aspi), or, if the ground is level, in furrows (uachos) in carefully weeded soil. It is sometimes called the "stool height". Bad specimens have a camphoraceous smell and a brownish colour, and lack the pungent taste. For someone seated, the popliteal height is the distance from the underside of the foot to the underside of the thigh at the knees. Good samples of the dried leaves are uncurled, are of a deep green on the upper, and a grey-green on the lower surface, and have a strong tea-like odor; when chewed they produce a faint numbness in the mouth, and have a pleasant, pungent taste. The two most relevant anthropometric measurement for chair design is the popliteal height and buttock popliteal length. Since the 1980s, the cultivation of coca has become controversial because it is used for the manufacture of the drug cocaine, which is illegal in most countries.

Anthropometric statistics may be gathered for mass produced chairs. Since ancient times, its leaves have been used as a stimulant by the indigenous people of Venezuela, Colombia, Ecuador, Peru, Bolivia, Brazil, and northern Argentina; it also has religious and symbolic significance. Individuals may be measured for a custom chair. Coca is traditionally cultivated in the lower altitudes of the eastern slopes of the Andes. Actual chair dimensions are determined by measurements of the human body or anthropometric measurements. . By matching the shape of the occupant's buttocks, weight is distributed and pressure at any given point is reduced. The leaves are sometimes eaten by the moth Eloria noyesi.

A contoured seat pan attempts to distribute weight without padding. The flowers mature into red berries. Where padding is not desirable, contouring may be used instead. The flowers are small, and disposed in little clusters on short stalks; the corolla is composed of five yellowish-white petals, the anthers are heart-shaped, and the pistil consists of three carpels united to form a three-chambered ovary. For example, in hot climates, padding with fabric or plastic covers is often uncomfortable against the skin. A marked characteristic of the leaf is an areolated portion bounded by two longitudinal curved lines once on each side of the midrib, and more conspicuous on the under face of the leaf. There may be cases where padding is not desirable. The branches are straight, and the leaves, which have a green tint, are thin, opaque, oval, more or less tapering at the extremities.

Chairs that have padding that is the same density front and back will feel soft in the back area and hard to the underside of the knees. The plant resembles a blackthorn bush, and grows to a height of 2-3 m. Since most of the body weight is supported in the back of the seat, padding there should be firmer than the front of the seat which only has the weight of the legs to support. The plant is best-known in modern times for the drug cocaine that is manufactured from it. In lieu of padding, flexible materials, such as wicker, may be used instead with similar effects of distributing the weight. Under the older Cronquist system of classifying flowering plants, this was placed in an order Linales; more modern systems place it in the order Malpighiales. Spreading the area reduces the pressure at any given point. Coca (Erythroxylum coca), often spelled koka in Quechua and Aymara, is a plant in the family Erythroxylaceae, native to northwestern South America.

The same body weight over a smaller area means greater pressure on that area. Coca tea. A hard wood chair feels hard because the contact point between the occupant and the chair is small. Huallaga Valley. However, padding does distribute the weight by increasing the area of contact between the chair and the body. Coca-Cola. Padding will not shift the weight to different parts of the body (unless the chair is so soft that the shape is altered). Coca eradication.

Padding can be on the seat of the chair only, on the seat and back, or also on any arm rests and/or foot rest the chair may have. Many chairs are padded or have cushions. A sit-stand chair distributes most of the weight of the occupant to the feet. A kneeling chair adds an additional body part, the knees, to support the weight of the body.

A stool or other simple chair may have a simple straight or curved bar near the bottom for the sitter to place his/her feet on. Some chairs have foot rests. Reclining chairs typically have at least shoulder height backrests to shift weight to the shoulders instead of just the lower back. Headrests support the head as well and are important in vehicles for preventing "whiplash" neck injuries in rear-end collisions where the head is jerked back suddenly.

Shoulder height backrests support the entire back and shoulders. In general, backrests come in three heights: Lower back backrests support only the lumbar region. The back of the chair will support some of the weight of the occupant, reducing the weight on other parts of the body. However, reclining may not be suitable for chairs intended for work or eating at table.

In general, if the occupant is suppose to sit for a long time, weight needs to be taken off the seat area and thus "easy" chairs intended for long periods of sitting are generally at least slightly reclined. This may be more comfortable for some in reducing weight on the seat area, but may be problematic for others who have bad backs. A reclining seat and back will shift weight to the occupant's back. A lower seat may shift too much weight to the "seat bones" ("ischial tuberosities").

It may also result in no weight on the feet which means more weight elsewhere. A seat that is higher results in dangling feet and increased pressure on the underside of the knees ("popliteal fold"). Ergonomic designs distributes the weight of the occupant to various parts of the body. Easy chairs for watching television or movies are somewhere in between depending on the height of the screen.

Dental chairs are necessarily reclined. "Task chairs", or any chair intended for people to work at a desk or table, including dining chairs, can only recline very slightly; otherwise the occupant is too far away from the desk or table. Intended usage determines the desired seating position. Chair design considers intended usage, ergonomics (how comfortable it is for the occupant), as well as non-ergonomic functional requirements such as size, stackability, foldability, weight, durability, stain resistance and artistic design.

. See history of the chair for an extended look at chairs from antiquity to the modern day. Headrests for seats in vehicles are important for preventing whiplash injuries to the neck when the vehicle is involved in a rear-end collision. There may be separate headrests.

The back may extend above the height of the head. Likewise, the back and sometimes the seat are made of porous materials or have holes drilled in them for decoration and ventilation. The back often does not extend all the way to the seat to allow for ventilation. Chairs as furniture are typically not attached to the floor and so can be moved.

A chair mounted in a vehicle or in a theatre is simply called a seat. A separate footrest for a chair is known as an ottoman, hassock or poof. A chair for more than one person is a couch, sofa, settee, loveseat (two-seater without arm rest in between) or bench. Without back and arm rests it is called a stool.

Chairs also often have legs to support the seat raised above the floor. A chair is a piece of furniture for sitting, consisting of a seat, a back, and sometimes arm rests, commonly for use by one person. seat cycle strength of 100,000 repetitions of 125 pounds (57 kg) dropped from 2 inches (50 mm) above the seat. seat strength of 225 pounds (102 kg) dropped from six inches (150 mm) above the seat.

leg strength of 75 pounds (34 kg) applied one inch (25 mm) from the bottom of the leg. chair stability if weight is transferred completely to the front or back legs. chair backstrength of 150 pounds (68 kg). Metal, Metal mesh or wire woven to form seat.

Splint, ash, oak or hickory strips are woven. Caning, woven from rush, reed, rawhide, heavy paper, strong grasses, cattails to form the seat, often in elaborate patterns. Tape, wide fabric tape woven into seat, seen in lawn chairs and some old chairs. Fabric, simple covering without support.

Leather, may be tooled with a design. Wicker, woven to provide a surface with give to it. Stone, often marble. Molded plastic.

Metal seats of solid or open design. Stuffed fabric, similar to padded leather. Padded leather, generally a flat wood base covered in padding and contained in soft leather. Wood slats, often seen on outdoor chairs.

Solid wood, may or may not be shaped to human contours.

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