Understanding the musculo-skeletal system is important in predicting human strength and in avoiding injury through the appropriate design of tasks. There are approximately 200 bones in the human body. With the majority of the human body being made up of water, we need the structure provided by bones to stop from approximating bags of jello. The main function is to provide the internal framework for the body. The long bone provide links between the joints and are the lever arms to which tendons attach.
Ligaments connect bones at their articulations, the points where they come together.
This is the range through which various connected body segments can move The motion involves the interaction of two or more joints and muscles. When muscles contract they move bones, thereby changing their position and moving the body or changing its posture. As noted in the previous lecture on anthropometry, design should be based on the 5th-percentile limits when personnel must position their bodies to operate or maintain equipment, and on the 95th percentile to accommodate a full range of unrestricted movement. This should be considered a minimum requirement, with extentions to more extreme individuals in the population being a desirable goal. The spinal column is a bony system of particular concern to designers, because it is the site of many work-related injuries.