Levers

• The lever is the bone.
• The fulcrum is the joint.
• The effort is the muscular force.
• The load is the weight or resistance.
• Bones act as levers, rigid structures which rotate around a fixed point. This fixed point is known as the fulcrum and in the human body are the joints. The muscles that surround a joint create internal forces that move the bones they are attached to. When a muscle contracts, an effort is created. If this effort is large enough to overcome any load placed upon a lever, such as a weight held in the hand, it will pull on the lever to create movement.
• First class levers: Effort and load either side of the fulcrum in the middle.
• Second class levers: effort and fulcrum either side of the load in the middle.
• Third class levers: load and fulcrum either side of the effort in the middle.
• Mechanical advantage: second class lever systems where the effort arm id greater than the load arm. A large load can be moved with a relatively small effort.
• Mechanical disadvantage: third-class lever systems where the load arm is greater than the effort arm. A large effort is required to move a relatively small load.
• An example of a first class lever is the extension of the neck when preparing to head a football.
• An example of a second class level is the ball of the foot in the take-off phase of a high-jump.
• An example of a third class levers is the flexion of the elbow during a bicep curl.
• The distance from the fulcrum to the effort is known as the effort arm.
• The distance from the fulcrum to the load is known as the load arm.
• A lever is a rigid structure allowing movement.
• There are three orders of lever system depending on where the fulcrum is placed.
• 1st class levers have the fulcrum in the middle.
• 2nd class levers have the load in the middle.
• 3rd class levers have the effort in the middle.
• The effort arm is the distance between the effort and the fulcrum.
• The load arm is the distance between the load and the fulcrum.
• Mechanical advantage is where the effort arm is longer than the load arm.
• Mechanical advantage is in a 2nd class lever.
• Mechanical advantage allows a large load to be moved with a relatively small effort.
• Mechanical disadvantage is where the load arm is bigger than the effort arm.
• Mechanical disadvantage is in a 3rd class lever.
• Mechanical disadvantage means a large effort is required to move a relatively small load.
• An example of a 1st class lever is extension at the neck in preperation for a header in football. The fulcrum is the atlas and the axis, the effort is the trapezium, the load is the weight of the head, and the lever is the bones in the cranium and jaw.
• An example of a 2nd class lever is the plantar flexion in the ball of the foot in the take off phase of a high jump. The fulcrum is the ball of the foot; the effort is the gastrocnemius and soleius; the load is the body weight; and the lever is the tarsals and metatarsals.
• An example of a 3rd class lever is flexion at the elbow during the bicep curl. The fulcrum is the elbow; the effort is the bicep brachii; the load is the weight/resistance; and the lever is the radius and ulna.
• An advantage of a first class lever is they have good stability.
• A disadvatage of a first class lever is they have a limited range of motion.
• An advantage of a second class lever is mechanical advantage.
• An advantage of a second class lever is they have a high force of contraction.
• A disadvantage of a second class lever is they have a low speed of contraction.
• A disadvantage of a second class lever is they have a low range of motion.
• An advantage of a third class lever is theu have a high speed of contraction.
• An advantage of a third class lever is they have a large range of motion.
• A disadvantage of a third class lever is mechanical disadvantage.