In this blog article, you'll find a handy glossary of commonly used terms in ergonomics. It's a useful overview to quickly get to grips with the key concepts!
Herniated disc:
A condition of the back (lumbar disc herniation) or neck (cervical disc herniation) in which the intervertebral disc bulges out. In medicine, this condition is often abbreviated to HNP. Nerves can become trapped, which may cause severe pain or even nerve damage, resulting in loss of muscle function (for example, being unable to pull the foot up towards the shin) or a numb feeling. The pain can be mild, but also so severe that the patient can only move around on hands and knees.
Lumbago:
Lumbago, or a "slipped back", is a form of lower back pain that can sometimes radiate to the buttocks, thighs and legs, but not below the knee: if it does, it is sciatica or a herniated disc. Back pain is sometimes caused by specific treatable conditions.
Lumbago may be accompanied by other symptoms such as back stiffness (pain and tightness when moving the spine).
RSI (Repetitive Strain Injury):
An umbrella term for all kinds of complaints related to repeatedly performing the same movements over a long period, movements that are sometimes small and do not seem strenuous in themselves. Conditions associated with RSI include bursitis and tenosynovitis.
Osteoarthritis:
In medicine, this is the name for a condition affecting the cartilage in the joints.
In everyday language, osteoarthritis is also known as joint wear and tear. It develops when more joint cartilage is lost than the body can produce. The cartilage deteriorates and sometimes disappears completely. With osteoarthritis, the fluid in the joint also decreases. This fluid, called synovial fluid, is needed to keep the joint moving smoothly and to absorb shocks. As the joint cartilage wears away and the shock-absorbing fluid in the joints decreases, bones can rub against each other, which causes a great deal of pain. Osteoarthritis mainly occurs in the joints of the hands, knees, shoulders, neck and hips. In fact, virtually everyone over sixty has some degree of osteoarthritis visible on an X-ray; sometimes it starts at a considerably younger age.
Arthritis:
An inflammation of the joints that can be caused by rheumatic conditions (for example rheumatoid arthritis), injuries or bacterial infection (septic arthritis).
Arthritis should be distinguished from osteoarthritis: painful joints due to wear and tear, without any inflammation. Confusingly, the English name of this latter condition, osteoarthritis, also contains the word "arthritis".
Facet joints:
These are small movable joints of the spine that connect the vertebrae to each other. Without facet joints, the spine would be completely rigid. We would only be able to walk bolt upright and would move very stiffly.
The facet joints can become inflamed due to injury or arthritis, causing pain and stiffness. When the facet joints are affected, this usually causes pain not only at the site of the facet joint, but also radiating to the head, shoulders, buttocks and legs. To reduce the pain, a doctor may prescribe a facet joint block.
Disc:
An intervertebral disc is found in the spine between two individual vertebrae. Intervertebral discs consist of a ring of fibrous cartilage with a gel-like core in the middle. They are somewhat elastic and so help to absorb shocks. A herniated disc in the back is caused by damage to the intervertebral disc.
Scoliosis:
A sideways curvature of the back (spine), creating one or two curves.
It occurs to a greater or lesser degree in 4 out of 100 people. The spine usually also rotates around its axis (this is known as rotational scoliosis), causing a hump.
Lordosis:
A natural curvature of the spine in the front-to-back direction. In lordosis, the convex side of the spine faces forwards. Lordoses are found in the cervical and lumbar spine. A pronounced lordosis in the lower back is known as a "hollow back" (swayback).
Natural curvature:
If you look at your spine from the side, you'll see a double S shape, or 3 curves:
a hollow curve in your neck (= cervical lordosis)
a convex curve at the level of your thoracic vertebrae (= thoracic kyphosis)
a slight hollow curve in your lower back (= lumbar lordosis).
Right at the bottom you also have your sacrum. Some claim that it forms a 4th curve in your spine, but that's somewhat less important.
What matters more is that these curves provide a balance between stability, resilience and mobility.
So you see, "keeping your back straight" isn't quite right. Your back is at its strongest in its natural "hollow-convex-hollow" position.
Synchronous mechanism:
The synchronous mechanism combines a movement of the backrest with a matching movement of the seat. The backrest moves further than the seat.
