Body links, sometimes known as the link system, is a method of applying general engineering principles to the skeleton. You simply reduce each bone (in some cases groups of bones) into a straight line. So the skeleton now looks like a stick man.
Take a few minutes to familiarize yourself with body links and you will soon develop a greater understanding of how your own body moves and works.
Body links allow you to perform reach and accessibility assessments as well as physics calculations (like generating the moment created during a lifting action) on a basic model. The results are surprisingly close to using the dynamic, skeletal model in most cases.
The other benefit of the body link system is that joints are reduced to a simpler function as well. The joint is simply represented like a hinge with a range of motion in a plane on the X, Y, and Z axis.
It may not sound much easier at the moment, but it is, and that’s why they created visual aids. You can break the body down into some basic sections.
- The arm consists of 3 links: the upper arm, the lower arm and the hand with joints at the shoulder, elbow and wrist.
- The leg consists of 3 links: the upper leg, the lower leg and the foot with joints at the hip, knee and ankle.
- The spine consists of 3 links: the chest, the lumbar and the pelvis with links at the torso, waist and pelvis. The pelvis is represented by a large triangular link.
- The shoulders and spine link to the collar bone. The collar bone links to the neck which links to the head.
You probably already know how the leg and arm work. What might be new to you is the back and neck.
The spine is made up of 25 bones, but most of the time it acts like 3 pieces. The chest link makes up about 60% of the overall spine with the lumbar (the small of the back) and the pelvis splitting the remaining difference. The neck has two main pivot points, the top and bottom of the neck. Try moving each link in isolation until you get a knack for how they move.
Now you are probably wondering what this is good for. It is good for a lot of things.
- The simplified body structure makes it easy for you to draw out your own ergonomic setups using your personal measurements.
- The simplified joint movements aid in those layouts as well as calculate stress on your body. You could use the average joint movements or measure your own range of comfort for inclusion in your ergonomic setups.
- And the simplified understanding arms you with more knowledge in your quest to fit your world around you to your needs.
Now that you have finished this overview on body links you can find more detailed information in Part 1 of a series on body links.
