Transcript Document
An analysis of human movement: Joints, Muscles and Mechanics in specified sporting actions (including planes and axes)
• • What you need to know: Analyse shoulder and elbow action in push-ups, over-arm throwing and forehand racket strokes Analyse hip, knee and ankle action in running, kicking, jumping and squats.
Levers: You should be able to: 1. Identify and understand the 3 classes of lever and give examples of use in sporting actions.
2. Understand and Explain the relationship of levers to effective performance and the range and speed of movement.
3. Understand the concept of mechanical advantage and disadvantage
Movement Analysis: Dominos
Levers
• A lever consists of three main components, namely: – A pivot (fulcrum); – Weight to be moved (resistance) and – Source of energy (effort or force). In the body the skeleton forms a system of levers that allows us to move. The bones act as the levers, the joints are the fulcrums and the effort is provided by the muscle.
A lever has two main functions: 1.
To increase the speed at which a body can move.
2.
To increase the amount of resistance that can be overcome by a force.
• • Throughout draw example images Give an examples in Sport / Physical Activity
Examiner’s Tip:
• An easy way to remember the order of the components in a particular class of levers is the mnemonic; – ‘1, 2, 3, - FRE’ • Where 1, 2, 3 refers to the class of the lever and F, R, E refers to the middle component.
1. F – as the middle component 2. R 3. E
Classification of levers.
You need to be able to Name, sketch, and label this diagram • •
First Order Levers
In a first order lever the fulcrum is between the effort and the resistance. This type of lever can increase the effects of the effort and the speed of a body. • There are only two examples within the human body.
– An example of this type can be seen in the movement of the head and neck during flexion and extension and in the action of extending the limbs, for example, the arm.
– – Triceps – Effort Elbow – Fulcrum – Weight of the arm - Resistance / Load • Examples: Throwing, racket strokes and press-ups.
Classification of levers.
You need to be able to Name, sketch, and label this diagram • •
Second Order levers
Here the resistance lies between the fulcrum and the effort. This type of lever is generally thought to increase only the effect of the effort force (i.e. it can be used to overcome heavy loads).
• There is only one example of this type of lever system operating in the body.
– Plantarflexion of the ankle involves the use of a second order lever.
– – Joint at ball of the foot - Fulcrum Bones of the foot – Lever – – Body weight – Resistance / Load Muscle – Effort • Examples: Plantar / Dorsiflexing in running, kicking, jumping and when performing squats.
Classification of levers.
You need to be able to Name, sketch, and label this diagram • •
Third Order Levers
These levers are responsible for the majority of movements in the human body. They can increase the body’s ability to move quickly but in terms of applying force they are very inefficient. • • • Here the effort lies between the fulcrum and the resistance and can be seen in the forearm during flexion.
Other examples may include; Hip and knee flexion and extension that occurs during running, jumping and kicking.
The hip flexors, gluteal, quadriceps and hamstrings all act on the respective joint as a third class lever system.
Tasks to Tackle:
•
Label the fulcrum, effort and resistance for flexion of the elbow on this diagram:
Do not abbreviate.
The ‘Effort’ is labelled from the muscle’s insertion, not the muscle itself
•
Mechanical advantage and disadvantage
Force arm – the name given to the shortest perpendicular distance between the fulcrum and the application of force (effort).
• resistance arm – the shortest perpendicular distance between the fulcrum and the resistance. The force and resistance arm can be seen in the 3 rd order lever below:
Mechanical advantage and disadvantage
• When the resistance arm is greater than the force arm, the lever system is at a mechanical disadvantage. – This means that the lever system cannot move as heavy a load but can do it faster. • Mechanical advantage is when the force arm is longer than the resistance arm. – This means that the lever system can move a large load over a short distance and requires little force.
• Key term: mechanical advantage is when the force arm is longer than the resistance arm • Key term: mechanical disadvantage when the resistance arm is greater than the force arm
Mechanical advantage and disadvantage
•
Length of Lever.
Most levers in the body are third class levers and here the resistance arm is always greater than the effort arm (mechanical disadvantage). • • The longer the resistance arm of the lever the greater the speed will be at the end of it. This means that if the arm is fully extended when bowling or passing, the ball will travel with more force and therefore more speed. – The use of a cricket bat, racket and golf club all extend the arm and allow more force.
Activity:
• Compare potential forces being applied to muscles of comparable size – biceps in biceps curls and gastrocnemius in calf raises. – Try doing a biceps curl with a 10 kg bar. It is probably quite hard work, but look at the range of motion achieved; you can move your arm from being straight at the elbow to bring your hand up so it almost touches your shoulder. Biceps curls involve a third class lever system.
• Now use a second class lever system. – Raise yourself up onto your toes and back down again. You are moving a lot more than 10kg! But look at the limited range of movement at the ankle. Most people cannot point their toes sufficiently to get the angle anywhere near straight, and none can get their toes to touch their shin!
• The third class lever system gives an advantage by allowing a great range of movement but gives the disadvantage of limiting the amount of force that can be applied. The second class lever system gives the advantage of allowing much greater forces to be applied, but has the disadvantage of having a very limited range of movement.
Top Tip:
• AQA only ask you to analyse five joints. They are all 3 rd order levers except for the ankle which is a 2 nd order lever and extension of the elbow and knee joints which are 1 st order levers. • Name and sketch the lever system that operates at the ankle joint. [3] • What do you understand by the terms mechanical advantage and mechanical disadvantage [4]
Exam Questions
Jan 2012
Exam Questions
June 2011