In this lesson we look at the main components of your back, the different types of back injury, and how your own behaviour adds to the risk of injuring it.

Your back is a complex structure, made up of many parts. Three of them matter most here. The spine. The nerves. And the muscles, ligaments and tendons that support it all.

The main bone in your back is your spine. It provides the structural support for your whole body, and it is made up of bones called vertebrae, with intervertebral discs in between them.

The main nerve in your back is the spinal cord. The spinal cord is what connects the nerves in every part of your body back to your brain.

The supporting muscles, ligaments and tendons in your back all connect to the spine. Together they are what allow your body to move, to bend, and to hold a whole range of positions.

The spine runs all the way from the skull down to the pelvis. It is made up of thirty-three interlocking bones called vertebrae, stacked one on top of the other, forming a slight curve in the shape of the letter S.

Between the vertebrae lie the intervertebral discs. Each disc contains a gel-like material that works as a shock absorber. When you lie down, the discs draw fluid back in, and that takes the pressure off the spine.

The vertebrae are separated by these discs, and that is the weight bearing part of the spine. The discs are filled with a jelly-like substance, and they act as your back's shock absorber. They absorb fluid when you lie down, which removes pressure from the spine.

The spinal cord runs from the base of the brain, about two thirds of the way down the spine. From it, nerves branch out through small gaps between the vertebrae and connect with nerves throughout the whole body. Any tissue that presses on a nerve can cause pain. An inflamed muscle, for example, or a herniated disc.

So what do they actually do? Ligaments hold bones together at the joints. Tendons attach muscles to bones. And muscles have the ability to contract and relax. Three different jobs, working together.

A ligament sprain happens when a ligament is stretched or torn, usually from a direct injury or a sudden twist of the joint. You strain a muscle by stretching it too far, causing tiny tears in the tissue. The muscle is then weakened, and it may not hold the bones of your spine in place properly. That is what causes lower back pain. And muscles fatigue if they are never allowed to rest and recover.

Sometimes the back is injured by a single incident. Lifting something far too heavy, for example. But usually, an injury to the back is the result of cumulative misuse. Repeated poor postures and poor movements, carried out over months or years, that slowly damage your back.

Poor posture. Task repetition. An inactive lifestyle. Poor handling technique. All of these are examples of cumulative misuse. A poor technique, such as twisting while you lift, places your back, your arms and your neck under pressure. Over time, those movements cause real injury.

Task repetition means a task done over and over, continuously. Packaging, or sorting, for example. Repeated tasks increase the risk of injury, because you are putting the same strain on the same set of muscles, again and again.

Poor posture, whether you are sitting or standing, increases the strain on your back and your neck. Bad posture may not cause you any discomfort in the short term. But continual bad posture causes back pain in the long term. Your back muscles support your spine, so good posture makes problems far less likely.

If you carry excess weight and spend most of your time inactive, you are more likely to do harm to your back. Extra weight places additional strain on the load bearing joints. Regular exercise is essential to keep muscles and joints resilient. An inactive lifestyle does the opposite. It weakens them.