Introduction to Sports Biomechanics: Analysing Human Movement ...

way and is known as a rigid body. Human body segments, such as the thigh and
forearm, are often considered to be close enough approximations to rigid bodies to be
treated as such. The complete human body is not a rigid body, but there are sports
techniques, as in diving and gymnastics, in which a body position is held temporarily, as
in a tuck or pike. During that period, the performer will behave as if he or she were a
rigid body and can be described as a ‘quasi-rigid’ body. In most sport activities, the
human performer does not behave as one rigid body. We then need to use the following
model.
General motion and the human performer – the ‘multi-segmental’ model
Figure 3.5 General motion.
MORE ON MOVEMENT PATTERNS – THE GEOMETRY OF MOTION
Most human movements involve combinations of rotation and linear motion, for
example the cross-country skier shown in Figure 3.5.
Such complex motions can be represented by a linked, multi-segment model of the
performer, where each of the body segments is treated as a rigid body. The rigid bodies
are connected at the joints between body segments. Such movement patterns can be
very difficult to analyse, but simpler representations of the structure of the movement
can be very helpful, as we shall see below.
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