Biomechanics and Kinesiology in Sports
What the domain covers
Biomechanics applies mechanical principles to human movement. The exam tests Newton's laws, lever classes, types of motion, stability and muscle actions.
Core content
- Newton's first law: a body remains at rest or in uniform motion unless acted on by a force. Second law: force = mass × acceleration. Third law: every action has an equal and opposite reaction; ground reaction force in running is an example.
- A lever has a fulcrum, load and effort. First class: fulcrum between load and effort (seesaw; neck extension). Second class: load between fulcrum and effort (wheelbarrow; calf raise). Third class: effort between fulcrum and load (biceps curl); most human levers are third class.
- Motion: linear (straight line), angular (rotation about an axis) and general (combination).
- Stability improves with a wider base, a lower centre of gravity and the centre of gravity over the base.
- Muscle actions: isometric (no change in length), isotonic concentric (shortening), isotonic eccentric (lengthening) and isokinetic (constant speed).
Worked example
In a biceps curl, the elbow is the fulcrum, the biceps insertion is the effort and the hand-held load is the load. Because the effort lies between the fulcrum and the load, it is a third-class lever. In a calf raise, the toes are the fulcrum, body weight at the ankle is the load and the calf muscle is the effort; the load lies between fulcrum and effort, so it is second class. The reasoning depends on the positions of the three points.
Traps that cost marks
Reversing second- and third-class levers; calling isometric contraction a change in length; and describing torque as force alone rather than force times perpendicular distance.