Movement analysis: levers, planes and axes
Physical Education · GCSE · The School
The three classes
The order of FULCRUM, LOAD and EFFORT along the lever names the class. FIRST class has the fulcrum in the middle — the neck, nodding the head. SECOND class has the load in the middle — rising onto the toes at the ankle. THIRD class has the effort in the middle — a biceps curl at the elbow, and most sporting movements. Say what is in the middle and the class follows.
Mechanical advantage, and its price
A second-class lever has the effort arm longer than the load arm, so a smaller effort moves a larger load — mechanical advantage. The price is range and speed: the load moves a short distance slowly. A third-class lever is the reverse — it needs more effort than the load, and buys a large, fast range of movement. Neither is better; they answer different problems, which is why the body uses both.
Planes and axes
SAGITTAL plane, transverse axis: forward and backward movement — a somersault, a running stride. FRONTAL plane, sagittal axis: side to side — a star jump, a cartwheel. TRANSVERSE plane, longitudinal axis: rotation — a spin in skating, a discus turn. Pair each plane with its axis when you learn them; questions almost always ask for both together.
ACTION: rising onto the toes to reach a high ball. JOINT: the ankle. FULCRUM: the ball of the foot. LOAD: body weight, acting through the ankle. EFFORT: the calf muscles pulling on the heel. ORDER along the lever: fulcrum at the toes, load in the middle, effort at the heel — LOAD IN THE MIDDLE, so a SECOND-CLASS lever, which gives mechanical advantage and is why the calf can lift the whole body. Now the plane: the movement is up and down, forwards of the body, so SAGITTAL plane about the TRANSVERSE axis. Four labels and two sentences, and that is a full-mark answer. Try the same on a biceps curl and you should reach third class, sagittal plane, transverse axis.