Introduction

Biomechanics is the science of the movement of a living body — the way muscles, bones, tendons and ligaments work together to produce motion. It sits within the wider field of kinesiology, the study of human movement, and is both a primary science (it generates research) and an applied science (its findings are put to practical use in training and performance).

Biomechanics is not limited to the obvious actions of bones and muscles. It also reaches into the mechanics of blood circulation, kidney function and other body processes, and it extends beyond humans to animals, plants and even the mechanical behaviour of cells. For a single action such as a squat, a biomechanical view considers the position and movement of the feet, hips, knees, back, shoulders and arms all at once.

Movement always results from a force. In any physical activity several forces and motions occur together, and while most of the body's movement is driven by forces produced by our own muscles, this is not always so — a push from an opponent, for example, is an external force. The biomechanical study of motion deals with linear motion, velocity, speed, acceleration and momentum.

Motion itself can be of three kinds:

• Linear motion — movement in a straight line (the kind you are mainly asked to understand).
• Angular motion — movement in a circular path around a central point; almost every movement at a joint is angular. …