PE planes, axis, and levers

The frontal plane runs vertically through the body

It divides the body into the front (anterior) and the back (posterior)

Movements in this plane are sidewards movement of abduction and adduction

Practical example:

Abduction and adduction of the legs at the hips for example, doing a star jump, or the leg action in swimming breastroke

The transverse plane runs horizontally through the body

It divides the body into the upper (superior) and the lower (inferior) section

Movements on this plane are rotational 

Practical example:

Arm action (circumdation) when bowling in cricket with rotation at the shoulder joint

The sagittal plane runs vertically through the body

It divides the body into right and left sides

Movements on this plane are the up and down movements of flexion and extension

Practical example:

The leg action that takes place while running

To be able to explain how the body moves, it is useful to see the body as having imaginary lines or planes running through it

These planes divide the body in three ways:

• frontal plane
• transverse plane
• sagittal plane

Levers are important in movement because they allow efficiency and force to be applied to the body's movements

Many bones and muscles work together to form levers, a lever is a bone that turns on a joint

Levers are used to make a small amount of force into a much bigger force, this is known as gaining mechanical advantage

There are four parts to a lever:

• lever arm
• pivot (fulcrum)
• effort
• load

Bones act as lever arms

Joints act as pivots

Muscles provide the effort to move loads

Load forces are often the weight of the body parts that are moved or forces that are needed to lift, push or pull things

Levers can also be used to increase the force of movement, for example when throwing a javelin, small contractions of the arm and back muscles produce a much greater force at the end of the arm

The fulcrum is located between the effort force and the load force on the lever arm

First class levers can increase both the effects of the effort and the speed of a body

An example of this type of lever is the neck joint

Practical example:

At the neck heading a football

The load is between the fulcrum and the effort

Second class levers tend to only increase the effect of the effort force

If you raise up on your toes or plantar flex at the ankle, the second class lever comes into operation

Practical example:

At the ankle when standing on tiptoes reaching for a smash in badminton

The effort is between the fulcrum and the load

Third class levers can be used to increase the speed of a body

They are the most common type of levers in the human body 

Practical example:

At the elbow when doing a bicep curl

Some levers (1st and 2nd) provide mechanical advantage

This means that they allow you to move a large output load with a smaller effort

Load and effort are measured in Newtons (N)

Mechanical advantage is calculated as follows:

Mechanical advantage = Load ÷ Effort 

Example:

Where the load is 500N and the effort is 100N the mechanical advantage would be 500 divided by 100 = 5

An axis is a straight line around which an object rotates

The movement at a joint takes place on a plane about an axis

There are three axes of rotation:

• Frontal axis

example : cartwheel

• Transverse axis

example : somersault 

• Longitudinal axis 

example : pirouette

Q1: Give the three classes of lever (3 marks)

Q2: Explain what is meant by mechanical advantage (2 marks)

Q3: Draw a simple diagram showing the three planes of movement (3 marks)

Q4: Using three different practical examples, describe the axes of rotation (6 marks)