You are viewing a free preview of this lesson.
Subscribe to unlock all 6 lessons in this course and every other course on LearningBro.
This lesson introduces the three classes of lever as required by the Edexcel GCSE PE specification (1PE0 — Topic 1: Applied Anatomy and Physiology). The human body contains hundreds of lever systems — every time you move a limb, you are using a lever. Understanding how levers work allows you to analyse sporting movements and explain why certain joints and muscles are suited to certain actions. This lesson covers the three components of every lever system, the three classes of lever, and how to identify them using body and everyday examples.
A lever is a rigid bar that turns around a fixed point when a force is applied. In the human body:
Every lever system has exactly three components:
| Component | What It Represents in the Body | Symbol |
|---|---|---|
| Fulcrum (F) | The joint — the pivot point around which the lever rotates | F |
| Load (L) | The resistance being moved — the weight of the body part, an object, or an opponent | L |
| Effort (E) | The force applied by the muscle to move the load | E |
Exam Tip: Edexcel examiners expect you to identify the fulcrum, load and effort in any lever system. Always think: F = joint, L = weight/resistance, E = muscle force. If you are asked to "label" a lever diagram, these are the three labels you need.
The class of a lever is determined by the arrangement of the fulcrum, load and effort. There are three possible arrangements.
In a first class lever, the fulcrum is positioned between the effort and the load.
Arrangement: Effort — Fulcrum — Load
graph LR
E["Effort<br>(E)"] --- F["Fulcrum<br>(F)"] --- L["Load<br>(L)"]
style E fill:#27ae60,color:#fff
style F fill:#e74c3c,color:#fff
style L fill:#4a90d9,color:#fff
Everyday example: A seesaw. The pivot (fulcrum) is in the centre, with effort pushing down on one side and the load being lifted on the other.
Body example: Extension at the neck (nodding the head backwards).
| Component | In the Body |
|---|---|
| Fulcrum (F) | Atlanto-occipital joint (top of spine) |
| Effort (E) | Neck extensor muscles (pulling down at the back) |
| Load (L) | Weight of the face and front of the skull |
Key feature: First class levers can change the direction of a force and provide balance. They are relatively rare in the human body.
In a second class lever, the load is positioned between the fulcrum and the effort.
Arrangement: Fulcrum — Load — Effort
graph LR
F["Fulcrum<br>(F)"] --- L["Load<br>(L)"] --- E["Effort<br>(E)"]
style F fill:#e74c3c,color:#fff
style L fill:#4a90d9,color:#fff
style E fill:#27ae60,color:#fff
Everyday example: A wheelbarrow. The wheel (fulcrum) is at one end, the heavy load is in the middle, and you lift (effort) at the handles.
Body example: Plantarflexion at the ankle (rising onto tiptoes).
| Component | In the Body |
|---|---|
| Fulcrum (F) | Ball of the foot (ground contact point) |
| Load (L) | Body weight acting downward through the ankle |
| Effort (E) | Gastrocnemius pulling up on the heel (Achilles tendon) |
Key feature: Second class levers are power levers. The effort arm is always longer than the load arm, which means a large load can be moved with relatively less effort. This is why the calf muscles can lift the entire body weight when you rise onto tiptoes.
In a third class lever, the effort is positioned between the fulcrum and the load.
Arrangement: Fulcrum — Effort — Load
graph LR
F["Fulcrum<br>(F)"] --- E["Effort<br>(E)"] --- L["Load<br>(L)"]
style F fill:#e74c3c,color:#fff
style E fill:#27ae60,color:#fff
style L fill:#4a90d9,color:#fff
Everyday example: A pair of tweezers or a fishing rod. The pivot is at one end, the force is applied in the middle, and the object being moved is at the far end.
Body example: Flexion at the elbow (e.g. a bicep curl).
| Component | In the Body |
|---|---|
| Fulcrum (F) | Elbow joint |
| Effort (E) | Biceps brachii (inserts on radius, close to elbow) |
| Load (L) | Weight in the hand / weight of the forearm |
Key feature: Third class levers are speed and range of movement levers. A small contraction of the muscle close to the fulcrum produces a large, fast movement at the far end (the load). However, this comes at the cost of power — more effort is needed to move the load compared to a second class lever.
Exam Tip: Third class levers are the most common lever class in the human body. Most limb movements — bicep curls, kicking, throwing, striking — use third class levers because the body is designed to prioritise speed and range of movement over brute force.
| Feature | First Class | Second Class | Third Class |
|---|---|---|---|
| Arrangement | E — F — L | F — L — E | F — E — L |
| What is in the middle? | Fulcrum | Load | Effort |
| Body example | Nodding the head (neck) | Rising on tiptoes (ankle) | Bicep curl (elbow) |
| Everyday example | Seesaw | Wheelbarrow | Tweezers / fishing rod |
| Main advantage | Balance, direction change | Power (large load, less effort) | Speed and range of movement |
| How common in body? | Rare | Uncommon | Very common |
Think of the word FLE (Fulcrum, Load, Effort). For each class, the component in the middle shifts:
This gives you the order 1-2-3 = F-L-E. The middle letter changes each time.