Lever systems, examples of their use in activity and the mechanical advantage they provide in movement — AQA GCSE Physical Education

A lever is a rigid bar that turns about a fulcrum when a force (effort) is applied, moving a load. The three classes are defined by the order of fulcrum, load and effort along the lever. In a first-class lever the fulcrum sits between the effort and the load, as when the neck extensors hold the head steady at the atlanto-occipital joint. In a second-class lever the load lies between the fulcrum and the effort, as in a calf raise where the toes act as fulcrum, body weight is the load and the calf muscles supply effort. In a third-class lever the effort lies between the fulcrum and the load, as in a biceps curl at the elbow. Most levers in the human body are third class. To identify a class, locate the joint (fulcrum), the body part or weight being moved (load) and the muscle providing force (effort), then read their order.

A basic lever drawing shows a straight bar with three labelled points: the fulcrum (pivot), the load (resistance) and the effort (force). The class is shown by the order of these points along the bar. Draw a first-class lever with the fulcrum between the effort and the load, for example the head nodding at the neck joint. Draw a second-class lever with the load between the fulcrum and the effort, for example a calf raise with the toes as fulcrum, body weight as load and calf muscle as effort. Draw a third-class lever with the effort between the fulcrum and the load, for example a biceps curl with the elbow as fulcrum, the hand-held weight as load and the biceps as effort. Label each point clearly and add arrows for effort and load so the positioning is unambiguous.

A fulcrum is the pivot point of a lever system, the fixed point about which the lever rotates. In the body, joints act as fulcrums: the elbow joint is the fulcrum when the biceps brachii contracts to flex the forearm, and the ankle joint is the fulcrum during plantar flexion at take-off in a jump. The position of the fulcrum relative to the effort and the load determines the class of lever (first, second or third) and shapes the mechanical advantage the system provides. A lever with the fulcrum between effort and load is first class; with the load between fulcrum and effort it is second class; with the effort between fulcrum and load it is third class. Recognising the fulcrum in a sporting action lets you explain how force is transferred and how range or speed of movement is produced.

The load, also called the resistance, is the force a lever system must overcome. In the body it is provided by the weight of the body part being moved plus anything being lifted or pushed, and sometimes by an external resistance such as a ball or an opponent. During flexion of the elbow, the load is the weight of the forearm and hand, acting through the centre of mass of that segment. The position of the load relative to the fulcrum and the effort decides the lever class and influences mechanical advantage: a load placed closer to the fulcrum is easier to move, while a load further from the fulcrum requires a larger effort. Naming the load accurately in a sporting action lets you explain how the body produces or resists movement.

In a lever system the effort is the force the performer applies to make the lever turn about its fulcrum. It is applied at a point on the lever, at a distance from the fulcrum called the effort arm, and it acts against the load or resistance. In a first-class lever such as a pair of scissors the effort is applied at the handles; in a second-class lever such as a wheelbarrow the effort is applied at the handles while the load sits between fulcrum and effort; in a third-class lever such as a bicep curl the effort is applied between the fulcrum and the load. Naming the effort correctly means identifying which force the muscles supply and where it acts, not confusing it with the load the lever moves.

A linear lever diagram represents the lever as a straight bar with three labelled positions: the fulcrum (pivot), the load or resistance, and the effort. Draw the bar as a horizontal line, mark the fulcrum with a triangle or pivot symbol, and place the load and effort at their correct positions along the bar. In a first-class lever the fulcrum sits between load and effort; in a second-class lever the load sits between fulcrum and effort; in a third-class lever the effort sits between fulcrum and load. Add arrows for the direction of the effort and the load, and label each part clearly so the class of lever can be read from the diagram.

This criterion asks you to read a sporting action and name the joint movement happening at the elbow, the knee or the ankle. At the elbow, flexion bends the forearm towards the upper arm (the upward phase of a biceps curl) and extension straightens it (the downward phase). At the knee, flexion bends the lower leg backwards towards the thigh (the recovery phase of running) and extension straightens it (the drive phase of a jump). At the ankle, plantar-flexion points the toes down and lifts the heel (the push-off in a sprint or a jump), while dorsi-flexion pulls the toes up towards the shin (landing from a jump or preparing to kick a ball). Decide which joint the question names, then decide whether the angle at that joint is closing (flexion) or opening (extension), and at the ankle whether the toes go down (plantar) or up (dorsi).

A lever has a fulcrum (pivot), an effort (the force applied) and a load (the resistance to be moved). The effort arm runs from the fulcrum to the effort, and the load arm (resistance arm) runs from the fulcrum to the load. Mechanical advantage compares these two arms: it is the effort arm divided by the load arm. A lever gives mechanical advantage greater than 1 when the effort arm is longer than the load arm, so a smaller effort moves a larger load. In a first-class lever the fulcrum sits between effort and load (the neck when heading a ball). In a second-class lever the load sits between fulcrum and effort (the calf raising the heel). In a third-class lever the effort sits between fulcrum and load (the biceps flexing the elbow), and because the effort arm is short these levers usually give mechanical advantage below 1 but gain speed and range of movement.

Mechanical advantage compares how far the effort is applied from the fulcrum with how far the resistance (weight) is applied from the fulcrum. You calculate it by dividing the length of the effort arm by the length of the weight (resistance) arm. If the effort arm is 0.60 m and the resistance arm is 0.20 m, the mechanical advantage is 0.60 ÷ 0.20 = 3. A value greater than 1 means the lever multiplies the effort, so a smaller effort can move a larger resistance, though the effort then moves through a greater distance. A value below 1 means the effort must be larger than the resistance but the load moves further and faster. Keep both arm lengths in the same unit before dividing, because the ratio itself has no unit.

On a lever drawing, first locate the fulcrum (pivot). The effort arm runs from the fulcrum to the point where the effort force is applied; the resistance arm runs from the fulcrum to the point where the resistance (weight or load) acts. Label each arm along its own line, not the whole lever. Then compare the two arm lengths: a longer effort arm than resistance arm gives a mechanical advantage above 1, multiplying effort, as when a long crowbar lifts a heavy lid. A shorter effort arm than resistance arm gives a mechanical advantage below 1, so the effort must be larger but the load moves further and faster, as in a pair of tweezers. Calculate mechanical advantage as effort arm ÷ resistance arm to confirm your interpretation.

This criterion asks you to analyse basic movements by naming the type of movement shown in a sporting example. At each joint you identify the movement occurring and link it to the action in the sport. Flexion decreases the angle at a joint, as when the knee bends before a jump; extension increases the angle, as when the knee straightens to drive the body upward. Abduction moves a limb away from the midline, as when a gymnast lifts an arm sideways; adduction brings it back towards the midline. Rotation turns a bone around its own axis, as when a swimmer rotates the shoulder through the water. Circumduction combines these into a circular motion, as in a bowler's arm swing. Plantar flexion points the foot down and dorsiflexion lifts the toes up. Analyse each example by naming the joint, the movement and the direction of the change in angle.

This criterion focuses on flexion and extension at four joints: the shoulder, elbow, hip and knee. Flexion decreases the angle at a joint, and extension increases it. At the shoulder, flexion raises the arm forwards and upwards, as in a front crawl recovery, while extension returns the arm backwards, as in the pull phase. At the elbow, flexion bends the arm, as in a bicep curl, and extension straightens it, as in a throw. At the hip, flexion lifts the thigh forwards, as in a high knee lift, and extension drives the leg backwards, as in the push-off in running. At the knee, flexion bends the lower leg backwards, as in the recovery phase of running, and extension straightens it, as in the kicking action in swimming. Analyse each example by naming the joint and stating whether the angle decreases or increases.

Abduction and adduction are antagonistic movements in the frontal plane at the shoulder joint. Abduction moves the arm away from the midline of the body, as when a swimmer lifts the arm out sideways to begin a front crawl stroke or a defender raises the arm to block. Adduction moves the arm back towards the midline, as when the same swimmer pulls the arm down and in towards the chest. The pair works because the deltoid (especially the middle fibres) abducts while the latissimus dorsi and pectorals adduct. In a multiple-choice question you must match the direction of movement to the correct term and to a sporting example, so check whether the arm is moving away from or towards the body's centre line before choosing.

Rotation at the shoulder is a turning movement of the humerus around its own long axis, occurring in the transverse plane. Medial (internal) rotation turns the front of the arm towards the body, as when a cricketer winds up to bowl or a thrower draws the arm across the chest. Lateral (external) rotation turns the front of the arm away from the body, as in the cocking phase of an overarm throw or a tennis serve. Rotation differs from abduction and adduction, which move the arm sideways, and from flexion and extension, which move it forwards and backwards. In a multiple-choice question, look for the word turning or twisting around the arm's axis and match it to the correct direction and example.

Circumduction is a movement at a ball-and-socket joint in which the distal end of the limb traces a circle while the proximal end stays still. At the shoulder, the humerus sweeps through flexion, abduction, extension and adduction in turn, so the hand describes a cone-shaped path. Picture a swimmer performing a full arm circle in front crawl, or a bowler rotating the arm through a complete loop: the elbow stays relatively fixed in space while the hand travels round. Circumduction combines several movements at one joint rather than being a single-plane action, and it differs from rotation, where the bone turns about its own long axis without the end travelling in a circle. Recognising this combination helps you describe shoulder action accurately in sporting examples and link it to the levers the arm forms.

At the ankle, plantar flexion points the toes down and away from the shin, as when a performer rises onto the balls of the feet or drives off the ground in a jump; dorsiflexion pulls the toes up towards the shin, as when the foot prepares to land or the heel strikes first in walking. Link each action to a lever by naming the fulcrum, the effort and the load. In a weight-bearing take-off, the ball of the foot and toes stay on the ground and act as the fulcrum, the calf muscles (gastrocnemius and soleus) pull through the Achilles tendon as the effort, and body weight is the load, giving a second-class lever arrangement. Dorsiflexion is produced by the tibialis anterior pulling the top of the foot upwards.

This guidance row tells you how the specification wants lever work connected to real activity. The applied anatomy and physiology content on page 9 pairs a joint type with the movement it produces; this section goes further and pairs a named sporting action with the type of movement occurring at a named joint, then with the lever system involved. The listed sporting actions are examples, not a closed list, so you should be able to take any action from your own sport and analyse it. A sound method is: name the action, identify the joint and the bones forming the lever, state the movement type (for example flexion at the elbow), classify the lever by the order of fulcrum, load and effort, then judge the mechanical advantage. Use this to plan revision and to check your own answers rather than to memorise a fixed set of exam questions.

A lever has a fulcrum, an effort and a load, and its class depends on which of the three sits between the other two. At the elbow in a push-up or a football throw-in, the elbow joint is the fulcrum, the triceps provide the effort, and the body weight or ball provides the load. The fulcrum lies between effort and load, so this is a first-class lever. A first-class lever can give either a mechanical advantage or a speed advantage depending on where the effort and load sit relative to the fulcrum. Learn to name the three points first, then decide the class from their order rather than from the movement itself.

At each joint a lever turns about a fulcrum, and the joint actions you name must match the movement observed. In running, the hip alternates flexion to drive the thigh forward and extension to push the leg back, while the knee flexes to bring the heel up and extends to straighten the leg, and the ankle uses dorsiflexion (toes up) and plantar flexion (toes down) to push off. In kicking, the hip flexes to swing the thigh forward and the knee extends to strike, with the ankle plantar flexing to point the foot. In a standing vertical jump the hip, knee and ankle extend together to drive the body upward, then flex to absorb landing. In a basic squat the hip flexes, the knee flexes and the ankle dorsiflexes as you lower, then all extend as you stand.

This item asks you to identify the shoulder action during a legal cricket bowling delivery and to connect it to the lever system. In the bowling action the shoulder rotates and circumducts through the delivery stride: the arm swings from behind the body, over the top and through, with the shoulder joint acting as the fulcrum. A legal delivery requires the bowling arm to be straight at the moment of delivery, so the elbow does not straighten to propel the ball; the shoulder generates the swing. The upper arm and forearm act as the lever, the shoulder muscles apply the effort and the ball is the load. Read the question to see whether it asks about the shoulder joint action or the lever class before choosing.