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 3rd 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 3rd order levers except for the ankle which is a
2nd order lever and extension of the elbow and
knee joints which are 1st 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
Jan 2012: Marking Scheme
June 2011: Marking Scheme