Movement Analysis: Lever Systems in Sport
Lever systems in the body work by applying an effort force, generated by a muscle, to move a load around a fixed fulcrum, usually a joint.
Before you start
Make sure you're comfortable with these topics first:
Method
- For any sporting movement, first identify the joint acting as the fulcrum, the muscle providing the effort, and what is being moved (the load).
- Establish the order of fulcrum, load and effort along the lever to classify it as first, second or third class.
- Learn one clear body example of each class: first class at the neck (nodding), second class at the ankle (standing on tiptoes), third class at the elbow (a biceps curl).
- Learn the mechanical advantage equation: mechanical advantage = length of effort arm divided by length of load arm.
- When calculating mechanical advantage, always state the equation, substitute the measurements given, and give a clear numerical answer, then interpret whether it is above or below 1.
- Learn what mechanical advantage above and below 1 means for performance: above 1 means less effort is needed than the load (favours force), below 1 means more effort is needed than the load but the load moves further and faster than the effort point (favours range of movement and speed).
Worked example
During a biceps curl, the effort (the biceps muscle) acts 5 centimetres from the elbow joint, and the load (a hand weight) is held 35 centimetres from the elbow joint. Calculate the mechanical advantage of this lever system, and explain what the result means for the force needed to lift the weight.
- Identify the lever class: this is a third-class lever, since the effort (biceps) acts between the fulcrum (elbow) and the load (hand weight).
- State the equation: mechanical advantage = length of effort arm / length of load arm.
- Substitute the values given: 5 / 35.
- Calculate: 5 / 35 = 0.14 (to 2 decimal places).
- Interpret the result: because the mechanical advantage is below 1, the effort force needed from the biceps must be greater than the weight of the load, but in exchange the hand moves through a much larger range of movement, and at greater speed, than the point where the biceps attaches to the forearm.
Practice questions
Try each question, then tap to reveal the answer.
Q1State the order of fulcrum, load and effort in a first-class lever.Show answer
Answer: The fulcrum is positioned between the load and the effort.
Q2Give a named body example of a first-class lever.Show answer
Answer: The neck, when nodding the head at the joint between the skull and the top of the spine.
Q3Give a named body example of a second-class lever.Show answer
Answer: Standing up onto tiptoes, at the ball of the foot.
Q4State the equation for mechanical advantage.Show answer
Answer: Mechanical advantage = length of effort arm divided by length of load arm.
Q5A second-class lever has an effort arm of 30 centimetres and a load arm of 10 centimetres. Calculate its mechanical advantage.Show answer
Answer: 30 / 10 = 3.
Q6Is the mechanical advantage of most third-class levers in the body above or below 1? Explain what this means.Show answer
Answer: Below 1 - the effort force needed is greater than the load being moved, but the load moves through a greater range of movement and at greater speed than the effort point.
Q7Explain one advantage of a lever system with a mechanical advantage above 1.Show answer
Answer: It requires less effort force than the size of the load being moved, since the effort arm is longer than the load arm, which favours lifting or moving heavy loads.
Exam-style questions
Written in the style of a GCSE Physical Education exam paper, with a full mark scheme.
State which class of lever is most common in the human body.
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A first-class lever has an effort arm of 8 centimetres and a load arm of 20 centimetres. Calculate the mechanical advantage of this lever, showing your working.
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A shot putter uses their arm as a third-class lever to release the shot. The effort (triceps) acts 4 centimetres from the elbow joint, and the shot in the hand acts 32 centimetres from the elbow joint. Calculate the mechanical advantage of this lever system, and evaluate why a third-class lever, despite its low mechanical advantage, is well suited to this movement.
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See real GCSE Physical Education past-paper questions, with official mark schemes →
Free printable worksheet
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