Learn about and revise movement analysis with this BBC Bitesize GCSE PE ( Eduqas) study Levers in our body are formed from bones, joints and muscles. Muscles generate tensile forces and apply moments at joints with short lever arms in In the human body there are more joints and muscles than are necessary for Newton's laws of motion give a clear relationship between the changing. The applied force, or effort, is used to move a resistance, or load. In the human body, the joints are fulcrums, and the bones act as levers.
All three types are found in the body, but most levers in the human body are third class. A first-class lever has the axis fulcrum located between the weight resistance and the force figure 1. An example of a first-class lever is a pair of pliers or scissors. First-class levers in the human body are rare.
Lever Systems: Bone-Muscle Relationships : Anatomy & Physiology
One example is the joint between the head and the first vertebra the atlantooccipital joint figure 1. The weight resistance is the head, the axis is the joint, and the muscular action force come from any of the posterior muscles attaching to the skull, such as the trapezius. In a second-class lever, the weight resistance is located between the axis fulcrum and the force figure 1. In the human body, the joints are fulcrums, and the bones act as levers.
The load is the bone itself, along with overlying tissues and anything else you are trying to move with that lever. Power Versus Speed A lever allows a given effort to move a heavier load, or to move a load farther and faster, than it otherwise could.The 6 Types of Joints - Human Anatomy for Artists
If the load is close to the fulcrum and the effort is applied far from the fulcrum, a small effort exerted over a relatively large distance can move a large load over a small distance. Such a lever is said to operate at a mechanical advantage and is commonly called a power lever.
For example, a person can lift a car with a power lever or jack. The car moves up only a small distance with each downward push of the jack handle, but relatively little muscle effort is needed. Lever systems operating at a mechanical advantage and a mechanical disadvantage. When using a jack the load lifted is greater than the applied muscular effort.
When using a shovel to lift dirt, the muscular force is greater than the load lifted. If, on the other hand, the load is far from the fulcrum and the effort is applied near the fulcrum, the force exerted by the muscle must be greater than the load to be moved or supported. This lever system is a speed lever and operates at a mechanical disadvantage.
BBC Bitesize - GCSE Physical Education - Movement analysis - Eduqas - Revision 1
Speed levers are useful because they allow a load to be moved rapidly or a large distance with a wide range of motion. Using a shovel is an example. Regardless of type, all levers follow the same basic principle: Other muscles attach to skin muscles of facial expressionClasses of levers.
The surfaces of the bone making up the joint have a layer of hyaline cartilage, the articular cartilage, which forms a smooth surface for easy movement. Bone ends may be surrounded by a joint capsule, which secretes fluid for lubrication and nutrition.
Joint motion is usually pain free, but age, injury, and some diseases damage the articular cartilage, resulting in arthritis. Biomechanics applies the principles of physics to human movement.
Some joints work like levers, others like pulleys, and still others like a wheel-axle mechanism. Most motion uses the principle of levers. A lever consists of a rigid "bar" that pivots around a stationary fulcrum. In the human body, the fulcrum is the joint axis, bones are the levers, skeletal muscles usually create the motion, and resistance can be the weight of a body part, the weight of an object one is acting upon, the tension of an antagonistic muscle, and so forth.
Levers are classified by first, second, and third class, depending upon the relations among the fulcrum, the effort, and the resistance. First-class levers have the fulcrum in the middle, like a seesaw. Nodding the head employs a first-class lever, with the top of the spinal column as the fulcrum.
Second-class levers have a resistance in the middle, like a load in a wheel-barrow.
The body acts as second-class lever when one engages in a full-body push-up.