Wednesday 6th July 2016 Lever Systems: L.O.  What are the benefits of different levers on sports performance?

A reminder of how a lever works in our body… First, second and third class levers and their use in physical activity and sport A reminder of how a lever works in our body… The joints of our skeleton not only allow movement, THEY ALSO ACT AS LEVERS The joint itself is the fulcrum (pivot) The effort is provided by the contracting muscles attached to the bone (think of the muscles acting as pulleys) The ‘load’ comes from the body part being moved and any implement used for sport (e.g. a bat or racquet) The human body is a system of levers and pulleys, this enables us to move

Levers have two functions: To move the load a greater distance or through a greater range of movement The closer effort is to the fulcrum, the greater the distance moved To apply force (strength) to an object - NB remember the longer the lever distance from the effort to the fulcrum the greater the force generated E.g. using a wheel brace enables a motorist to undo the nuts on his/her wheels

First Class Levers: In a first-class lever, the fulcrum is located between the load and the effort. A seesaw is a first class lever. First class levers in the body are rare, and few exercises utilise them. Examples, however, are exercises that require elbow extension, such as dumbbell triceps extensions and triceps dips. In each of these exercises, the elbow joint serves as the fulcrum, which lies between the load and the effort applied by the triceps muscle behind the elbow. In a first-class lever, the fulcrum is located between the load and the effort. A seesaw is a first class lever. First class levers in the body are rare, and few exercises utilise them. Examples, however, are exercises that require elbow extension, such as dumbbell triceps extensions and triceps dips. In each of these exercises, the elbow joint serves as the fulcrum, which lies between the load and the effort applied by the triceps muscle behind the elbow. This is a lever where the fulcrum occurs between the effort and load

Second Class Levers: Second-class levers also are fairly rare in the body. In a second-class lever, the load lies between the fulcrum and the effort, as in a wheelbarrow. Exercises that require extending the ankle, such as seated or standing calf raises, employ a second-class lever. In a calf raise, the load (the weight of the body) is positioned between the fulcrum at the toes and balls of the feet, and the effort, which is applied by the calf muscles pulling on the heel. This lever occurs when the load is between the effort and the fulcrum.

Third Class Levers: This lever occurs when the effort lies between the fulcrum and load. This is very common in human movement This is the most common form of lever in the human body In terms of applying force this is a very inefficient lever, but it allows speed and range of movement An example within the body is the forearm during flexion

CLASSIFICATION OF LEVERS: Class 1 lever : fulcrum between effort and load see-saw lever found rarely in the body example : Elbow (extension) : Neck (nodding) Class 2 lever : load between fulcrum and effort wheelbarrow lever, load bigger than effort example : Toes (Calf raise) Class 3 lever : effort between fulcrum and load effort bigger than load, most common system found in body example : Knee (flexion & extension) : Elbow (flexion) .

Two benefits of levers: Mechanical advantage and disadvantage (in relation to loads, efforts and range of movement) of the body’s lever systems and the impact on sporting performance Two benefits of levers: Large loads can be moved with a relatively small amount of effort The distance a load can be moved, or the speed with which it can be moved, can be increased without an increase in effort

Levers in the body… https://www.youtube.com/watch?v=ny8k7 LUUIEk

‘Load Arm’ and ‘Effort Arm’: To work out the benefit of a particular lever, you need to look at the length of the two arms… The distance from the load to the fulcrum is known as the ‘load arm’ The distance from the effort to the fulcrum is known as the ‘effort arm’

Mechanical advantage: When a lever’s effort arm is longer than its load arm it is said to have a mechanical advantage Levers with mechanical advantage can move large loads with less effort Second class levers always have a mechanical advantage

Mechanical advantage in the take-off in long jump: This example of a second class lever has a mechanical advantage because the effort arm is longer than the load arm The effort produced by the muscles, which is relatively small, is able to drive the full weight of the athlete off the ground

Mechanical disadvantage: When a lever’s load arm is longer than its effort arm it is a mechanical disadvantage Whilst they are said to be a ‘disadvantage’, third class levers are able to increase the speed at the end of the lever arm Third class levers always have a mechanical disadvantage

Third class levers at work in the hip joint: The hip joint is at a ‘disadvantage’ as it has to apply a greater force to lift the load Third class levers can take a small movement near the fulcrum and make a large movement where the load is. This provides a large range of movement and a high speed being produced

First class levers: mechanical advantage and disadvantage With first class levers, the position of the fulcrum is key… If the fulcrum is closer to the load, then a small amount of effort will result in more powerful movements of the load If the fulcrum is closer to the effort, more effort is need to move the load, but it can be moved at a higher speed

A summary of the effects/benefits of levers: First Class - can increase both effort and the speed of a body Second Class - tend only to increase the effect of the effort force Third Class - can be used to increase the speed of a body