Movement Analysis - Levers Planes and Axes
Lever Systems
A lever is a rigid bar (bone) that turns around a fixed point (joint) when a force is applied (muscle contraction). Understanding lever systems helps explain how the body creates movement efficiently.
Components of a Lever
| Component | In the Body | Definition |
|---|---|---|
| Fulcrum (pivot) | Joint | The fixed point around which the lever rotates |
| Effort | Muscle force | The force applied to move the lever |
| Load (resistance) | Weight of the body part or external weight | The force that the lever must overcome |
Classes of Lever
There are three classes of lever, defined by the arrangement of the fulcrum, effort, and load:
| Class | Order | Example in Sport | Mnemonic Position |
|---|---|---|---|
| First class | Fulcrum in the middle (Effort – Fulcrum – Load) | Heading a football (neck joint), seesaw | Like a seesaw |
| Second class | Load in the middle (Effort – Load – Fulcrum) | Calf raise / plantar flexion at the ankle | Like a wheelbarrow |
| Third class | Effort in the middle (Load – Effort – Fulcrum) | Bicep curl (elbow joint), kicking a ball | Most common in the body |
Third class levers are the most common in the human body because they allow a large range of movement even though they require more effort.
Mechanical Advantage
- Mechanical advantage = when the effort arm is longer than the load arm. The lever multiplies force (second class levers have this).
- Mechanical disadvantage = when the load arm is longer than the effort arm. The lever sacrifices force for speed and range of movement (third class levers have this).
Exam note: You may be given a diagram and asked to identify the class of lever, or to label the fulcrum, effort, and load for a given sporting action.
Planes of Movement
A plane is an imaginary flat surface that divides the body. Movement occurs along (within) a plane.
| Plane | Divides the Body Into | Movements in This Plane | Sporting Example |
|---|---|---|---|
| Sagittal (median) | Left and right halves | Flexion, extension | Running, cycling, squats |
| Frontal (coronal) | Front and back halves | Abduction, adduction | Star jumps, cartwheel (arms) |
| Transverse (horizontal) | Top and bottom halves | Rotation | Discus throw, golf swing, pirouette |
Axes of Rotation
An axis is an imaginary line around which the body or a body part rotates. Each axis is perpendicular (at 90°) to its associated plane.
| Axis | Direction | Associated Plane | Sporting Example |
|---|---|---|---|
| Transverse (horizontal) | Runs left to right across the body | Sagittal plane | Front somersault, running stride |
| Sagittal (anteroposterior) | Runs front to back through the body | Frontal plane | Cartwheel |
| Longitudinal (vertical) | Runs top to bottom through the body | Transverse plane | Pirouette, spinning in ice skating |
Linking Planes and Axes
The key rule is: movement occurs in a plane and around the axis perpendicular to that plane.
| Plane | Axis | Movement | Example |
|---|---|---|---|
| Sagittal | Transverse | Flexion / extension | Kicking a ball |
| Frontal | Sagittal | Abduction / adduction | Jumping jack arms |
| Transverse | Longitudinal | Rotation | Golf swing |
Types of Movement at Joints
| Movement | Definition | Example |
|---|---|---|
| Flexion | Decreasing the angle at a joint | Bending the elbow |
| Extension | Increasing the angle at a joint | Straightening the knee |
| Abduction | Movement away from the midline of the body | Raising the arm sideways |
| Adduction | Movement towards the midline of the body | Lowering the arm back to the side |
| Rotation | Turning a bone around its long axis | Turning the head left or right |
| Circumduction | A combination creating a cone-shaped movement | Bowling in cricket |
| Plantar flexion | Pointing the toes downward | Pushing off in a sprint |
| Dorsiflexion | Pulling the toes upward | Landing phase of a jump |
Exam Tips
- When analysing a sporting movement, state all four elements: the joint, the movement, the plane, and the axis.
- For lever questions draw a simple diagram and label F (fulcrum), E (effort), L (load). Then determine the class.
- Remember the mnemonic 1-2-3 = FLE: Fulcrum in the middle (1st), Load in the middle (2nd), Effort in the middle (3rd).
- A common exam question: "Identify the plane and axis of movement when a gymnast performs a somersault" — answer: sagittal plane, transverse axis.
- Practise applying planes and axes to whole-body movements (somersault, cartwheel, spin) as well as isolated joint movements (flexion at the knee).