Library · Physiology
The body as a system of levers
Make it clearer
When you pull a nail with the claw of a hammer, the handle acts as the bar and the head resting on the wood acts as the fulcrum. Your body works the same way: the bones are the rigid bars of a system of levers.
The fulcrum is provided by the ends of the bones where they meet, inside the synovial joints, which have a cavity and fluid and are the freely movable ones.
Two forces are still missing. The load is what has to be overcome: the object you lift, or any resistance to movement; your own head is a load when you lift it. The effort, the force that is applied, comes from the contraction of skeletal muscle.
For a muscle to pull on a bone, it has to be anchored to another bone that does not move. The end that moves, the one attached to the bone that is going to be pulled, is called the insertion; the fixed end is called the origin.
And that is what matters: how that connection is built determines how much force you get, at what speed and over what range.
In brief
The musculoskeletal system works as a system of levers: the bones are the rigid bars.
A hammer's handle and head when pulling out a nail.
The articular ends of the bones, inside the synovial joints, act as the fulcrum.
The load is the object being lifted or any resistance; the effort comes from the muscle.
The end that pulls the bone is the insertion; the fixed end is the origin.
Force, speed and range of motion depend on that connection.
Sources (1)
- OpenStax, Rice UniversityAnatomy and Physiology 2e, 11.1 Interactions of Skeletal Muscles, Their Fascicle Arrangement, and Their Lever SystemsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated