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【Farewell Pain Special Topic】Choose the right chair cushion to support the waist and protect the spine Find the correct sitting posture and bid farewell to pain

【Farewell Pain Special Topic】Choose the right chair cushion to support the waist and protect the spine Find the correct sitting posture and bid farewell to pain

Article: Zhang Shumei “Ming Pao”

(Hong Kong News) It is true that “going to work is harmful to your health”. Many people sit and work in the office all day, which is prone to various pains.

Prolonged sitting and poor posture are one of the curses. Some people will add functional seat cushions and lumbar cushions, hoping to relieve the pressure on the lower back. There is a dizzying array of styles, one that claims to be ergonomic, one that claims to correct sitting posture, and some that claim to reduce stress.

In this issue, experts are invited to dismantle it, from the design to the materials used, to find a good working posture together.

Physiotherapist: Hu Cunxiao

What is a good seat and lumbar cushion?

“It is suitable to help us maintain a neutral position without exerting ourselves when sitting down.” What is a neutral position?

Hu Cunxiao, a visiting assistant professor and registered physiotherapist at the Department of Rehabilitation Sciences of the Hong Kong Polytechnic University, stood up and explained that, viewed from the side, a person’s physiological curvature is naturally S-shaped. pain, lumbago”. When standing up, you can maintain this posture without using any force, but when you sit down, your center of gravity will move forward, and your back will curl up as soon as you relax. You need to use force to maintain a neutral posture. Therefore, the seat needs good support. A suitable seat cushion and lumbar cushion can help Help users maintain a neutral posture naturally when sitting down.

The product advertises “ergonomics”

Products on the market that help correct sitting posture and relieve back pressure can be roughly divided into three categories in terms of design: integrated ergonomic back cushions, seat cushions, and lumbar cushions.

In recent years, more and more products advertise “ergonomics”, but what is ergonomics?

The public’s understanding of ergonomics is mostly about physical ergonomics, that is, products are designed according to different body shapes and structures of the human body, so that users can reduce the pressure on the body caused by bad posture when using the product.

Lu Zhiheng, deputy director of the Public Design Research Office of the School of Design, Hong Kong Polytechnic University, pointed out that ergonomics not only takes into account the physical aspect, but also the psychological and organizational aspects. Psychological ergonomics (cognitive ergonomics), as the name suggests, is to make users feel psychologically comfortable when using products, such as the dazzling lights of e-sports keyboards, which increase the sense of engagement and stimulation when playing games; as for organizational ergonomics (organizational ergonomics) ), “Pay attention to the convenience of the use process. Even if a chair is comfortable for people to sit on, if it is troublesome to assemble and use, it is not a good ergonomic consideration.”

There is a kind of one-piece ergonomic back cushion, which is like a mini chair, covering the buttocks and lower back. The bottom is curved. Hu Cunxiao pointed out that it is similar to the design of a fitness ball, “the bottom will move, (when sitting ) To use different muscles and change the pressure position, so that the pressure will not be concentrated for a long time and feel more comfortable.” The backrest part imitates the curvature of the human spine, and it is claimed that sitting upright on the back of the chair can maintain the correct sitting posture, “but it depends on whether you fit the curvature of the seat cushion (backrest), everyone is different in height, and the concave position of the waist is different “A single style and size is not suitable for everyone. It is recommended to try a seat before buying.

Lu Zhiheng believes that “(this back cushion) only supports the lower back, and the upper back (for a long time) may unconsciously shrink inward, requiring effort to adjust the sitting posture”, and it may feel uncomfortable to use for a long time.

When a person maintains a neutral posture, that is, there is a concave position behind the neck and waist, the pressure on the spine is the lowest, and it is not easy to have neck pain and low back pain.

The raised part of the lumbar pad should be placed in the concave position behind the waist to support the lumbar spine.

Special Design: Adjustable Fit Chair

Hip-shaped seat cushion reduces pressure

Seat cushions come in a variety of designs, from boxy to hollow-centered and angled forward, with some more hip-shaped.

“The idea of ​​the seat cushion leaning forward is to make it easier for people to maintain a neutral posture.” Hu Cunxiao pointed out that this type of seat cushion adjusts the sitting posture by relying on the pelvis, which is thin in the front and thick in the back. Leaning forward makes it easier to sit up straight, because when the pelvis is tilted forward, the waist will be bent back relatively, so that you can maintain a neutral posture.” Lu Zhiheng added, “Many people concentrate when working, and the body will have the habit of slightly forward , the design with a forward angle is in line with user habits.”

As for the design of the seat cushion to follow the shape of the buttocks, the purpose is to minimize the pressure when sitting down. Hu Cunxiao explained, “The larger the contact point area, the smaller the pressure. On the contrary, the smaller the contact point, the greater the pressure on this point. .”

As for the hollow design in the middle, it is aimed at patients with hemorrhoids to increase the air permeability of the seat cushion.

The Korean honeycomb gel seat cushion, which has been very popular for a while, is covered with a grid of hexagonal holes. Hu Cunxiao pointed out that this will enhance the air permeability of the seat cushion: “The memory foam (and the buttocks) is tightly packed, and it is difficult to breathe, but the honeycomb design Each grid has a few recesses to allow air to come in and out, making it more breathable.”

The surface of the seat cushion is made of soft gel material, which can distribute pressure. However, both of them think the effect of the honeycomb gel seat cushion is mediocre. Hu Cunxiao pointed out, “Unless the angle of the seat cushion is tilted forward, it is just an ordinary pressure-relief seat cushion.”

School of Design, Hong Kong Polytechnic University
Deputy Director of Public Design Research Office
Lu Zhiheng

Hong Kong Polytechnic University
Full-time tutor of the Department of Applied Physics
Cai Shaokang

Lumbar pad double wings cover the lower back for more comfort

Many office workers put lumbar pads on the chairs, some of which are one piece, and some are designed with double wings, which separate the left and right parts like the back, and the angle and height can be adjusted according to the curved surface of the back.

“Separating the two parts is designed to better fit the arc of the back. (The double-wing design) can increase the contact surface between the back and the lumbar pad.” Compared with the one-piece design, Hu Cunxiao believes that separating the two parts can cover better, More comfortable, but not much difference in correcting sitting posture.

He said that he has seen many people use the wrong lumbar cushion, just put it on the chair, and it does not fit the waist arc; if it is correct, you should buy some lumbar cushions that can be adjusted in height, or can be tied to the back of the chair. In the deepest part of the seat cushion or chair, lean on the back of the chair, and then take pictures of the lumbar cushion on the arc of the waist to find the position where the lumbar spine needs the most support.

The coverage of some lumbar pads extends from the lower back to the upper back, so that the thoracic spine can also be supported. Hu Cunxiao thinks it is unnecessary, “The thoracic spine is not so flexible, and it is relatively stiff. Covering the upper back just adds to the comfort.”

Lu Zhiheng thinks that this kind of back cushion that can support the entire waist and even the upper back is the most comfortable, but the price is generally more expensive. Also need to buy different sizes.”

In terms of materials, Hu Cunxiao pointed out that soft materials can relieve the pressure when sitting down, “but not too soft, otherwise the sitting posture cannot be corrected.”

Foam durable and better supporting capacity

Most products on the market use foam as a filling material. Cai Shaokang, a full-time instructor of the Department of Applied Physics at the Hong Kong Polytechnic University, pointed out that foam is more durable and flame-resistant. Among them, medium-density and high-density foam are more suitable for seat cushions. The supporting force is better, because the higher the foam density, the greater the pressure it can withstand.

Memory foam is also one of the commonly used materials. It is durable, soft, and also has a good supporting force. It can evenly distribute the weight on the surface of the object to achieve a decompression effect.

Some of the seat cushions and lumbar cushions made of memory foam claim to be able to “memorize” sitting postures, but Cai Shaokang has reservations, because the seat cushions are not as thick as mattresses and pillows, and the memory effect may not be obvious. As for latex, it is more commonly used in lower-priced seat cushions or lumbar cushions. He pointed out that although the resilience is good, it is more bulky, non-flammable and prone to aging, and the product life may be shorter.

“Many people come to see a doctor with neck pain and low back pain. Most of them are not injured, but because of poor posture (causing the disease).” Therefore, Hu Cunxiao believes that all office workers need to use functional seat cushions and lumbar cushions to prevent sitting posture. Problems caused by bad habits, but also avoid sitting for a long time, get up and move around every 30 minutes or 1 hour.

An ill-fitting chair affects posture

Lo Chi-hang, who was in charge of the project, said that unfit chairs affect the sitting posture of schoolchildren, so a detachable ergonomic chair was designed. The back cushion is made of high-density foam and designed with a curved surface according to the curvature of the lumbar spine. There are two thickness options and the height can be adjusted to fit school children of different shapes.

(Figure A) Waist decompression
1. Stand up straight, hands on hips, looking forward
2. Bend your waist and bend back, then straighten back to the starting position, then bend back, repeat the movement, without stopping for each movement

(Fig. B) Thoracic spine decompression
1. Sit up straight with your back against the back of the chair
2. Put your hands behind your neck, lean your upper body back, return to the center, and lean back again, repeat the movement without stopping at each movement

Hu Cunxiao pointed out that many office workers are used to not sitting on the back of the chair (left), or even sitting on half of the chair; the correct sitting posture (right) should be to keep the back close to the back of the chair, maintain the center of the body, keep the feet at 90 degrees to the ground, and keep the wrists out of the way. higher than palm.

Timely exercise: bend your waist backward to relieve the pressure on the lumbar and thoracic spine

After sitting for a period of time, the muscles of the whole body are very tense. Physiotherapist Hu Cunxiao suggested getting up in time to do decompression exercises to relieve the pressure on the waist and thoracic spine. Do 5 sets a day, 10 times in each set.

Exacerbation of the condition or pain in the clawed hands, beware of the cubital tunnel syndrome

What is Cubital Tunnel Syndrome?

Have you ever tried to wake up due to hand pain or numbness in your sleep, but just move your wrist or fingers a little, and the numb pain will soon be relieved. What should you do when this happens?

If you often have this kind of numbness in your hands, you may be suffering from carpal tunnel syndrome (also known as carpal tunnel syndrome), cubital tunnel syndrome (also known as cubital tunnel syndrome) , or problems with the cervical spine. People have heard a lot about carpal tunnel syndrome, but cubital tunnel syndrome, which has become more common in recent years, is easily overlooked.

Related to bad posture external impact

Cubital tunnel syndrome is a peripheral compressive neuropathy caused by compression of the ulnar nerve in the cubital tunnel (see figure), which is second only to carpal tunnel syndrome in commonness. There are many causes of Cubital Tunnel Syndrome. The most common causes are poor posture or external impact. People who often put pressure on their elbows due to work or living habits are high-risk individuals. The following are some common causes:

1/ Fitness enthusiasts with overdeveloped triceps

2/Construction workers who often need to bear heavy loads, have degenerated elbows or nerve lines are oppressed by bone spurs

3/ The elbow position has been seriously injured

Symptoms extending from the inside of the elbow to the forearm

Patients will experience intermittent numbness and pain at the beginning of the onset. Since the ulnar nerve affects the little finger and the outer half of the ring finger, and it is also responsible for controlling the hand movements of the forearm muscles, many patients’ symptoms will extend from the inner side of the elbow to the Forearm and fingers. Generally speaking, the initial symptoms of patients are relatively mild:

◆Numbness and tingling in the inner elbow and forearm

◆Swelling and weakness

◆Intermittent numbness gradually extends to the little finger and ring finger

In severe cases, long-term numbness extends to the shoulder

Exacerbation of the condition or serious “claw hand” can cause long-term numbness extending to the shoulder.

If you seek medical treatment as soon as possible and cooperate with appropriate treatment, plus enough rest or stopping certain weight-bearing exercises, many patients can slow down their condition. If left untreated, the condition may worsen and a “claw hand” may appear. In severe cases, the following symptoms may occur:

◆Long-lasting numbness that may spread to the shoulder or forearm

◆Pain is stronger at night, and even wakes up the patient

The hand muscles controlled by the ulnar nerve gradually atrophy, forming a “claw hand”

◆Sluggish hand movements and lack of dexterity

◆Decreased hand grip strength, affecting hand mobility

The initial symptoms of Cubital Tunnel Syndrome are mild. Conservative treatment such as wearing protective gear and physical therapy can alleviate the symptoms.
The initial symptoms of Cubital Tunnel Syndrome are mild. Conservative treatment such as wearing protective gear and physical therapy can alleviate the symptoms.

Conservative therapy Wearing braces Physiotherapy

To diagnose Cubital Tunnel Syndrome, the doctor will usually make a clinical judgment first, check the pain and numbness near the elbow joint, and also test the patient’s hand grip, movement and hand touch to judge the severity of the disease.

In addition, nerve conduction tests and electromyography will be used to conduct detailed examinations to further understand the degree of ulnar nerve compression and whether there is muscle atrophy, and then provide suggested diagnostic methods.

For patients with early-stage cubital tunnel syndrome, in addition to suggesting to stop the bad movements that cause symptoms, they can also choose to cooperate with conservative treatment, such as wearing protective gear, physical therapy, taking or injecting non-steroidal anti-inflammatory drugs, etc. Numbness caused by compression of the bradyulnar nerve.

If the condition is more serious, the patient may consider surgical treatment according to the situation to relieve the pressure on the ulnar nerve. There are two types of surgery: “in situ decompression” and “anterior transposition”. The former is more suitable for patients with mild symptoms. It only needs to incise the thick ligament that compresses the ulnar nerve to release the compressed ulnar nerve; the latter needs to transfer the channel of the ulnar nerve to the front, and then rearrange the ulnar nerve, ligaments and tendons The membrane is positioned so that the ulnar nerve is no longer compressed.

Median Nerve Compression

Painful wrist tendon swelling

Carpal tunnel syndrome is pain caused by compression of the median nerve. People who use keyboards and mice for a long time are at high risk.

The carpal tunnel is a tube composed of the transverse carpal ligament and the carpal bone. The tube contains 9 tendons and the median nerve, which runs from the forearm to the palm of the hand and is one of the three nerve lines that produce sensation in the hand.

Carpal tunnel syndrome is caused by swelling of the tendons in the wrist, which puts pressure on the median nerve line in the carpal tunnel, causing pain and numbness. Tendon swelling can be caused by many things, related to repetitive wrist activities at work, such as lifting, prolonged use of keyboard and mouse, etc.

Elbow stiffness that makes it difficult to straighten

Other causes include local inflammation, gouty arthritis, and pregnancy. Sometimes in some cases of infection, such as tuberculosis infection or tumor, it will also cause compression of the median nerve line in the carpal tunnel.

The cubital tunnel is a duct covered by soft tissue and ligaments on the inside of the dorsum of the elbow, allowing the ulnar nerve to pass through the muscles on the inside of the arm, the palm, the little finger and part of the ring finger.

Cubital tunnel syndrome is caused by the compression of the ulnar nerve in the cubital tunnel. The pressure may be caused by fascia inflammation, elbow muscle atrophy, or osteophytes derived from degeneration of the elbow joint. The patient’s elbow joint is often stiff and difficult to straighten, which is mostly caused by previous trauma or excessive strain.

Text: Li Chongyi (orthopedic surgeon)

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