Introduction to Sports Biomechanics: Analysing Human Movement ...

THE BODY’S MOVEMENTS
Movements of the human musculoskeletal system
As we noted in Chapter 1, a precise description of human movement requires
the definition of a reference position or posture from which these movements are
specified. The two positions used are the fundamental (Figure 1.2(a)) and anatomical
(Figure 1.2(b)) reference positions. With the exception of the forearms and hands, the
fundamental and anatomical reference positions are the same. The fundamental
position of Figure 1.2(a) is similar to a ‘stand to attention’. The forearm is in its neutral
position, neither pronated (‘turned in’) nor supinated (‘turned out’). In the anatomical
position of Figure 1.2(b), the forearm has been rotated from the neutral
position of Figure 1.2(a) so that the palm of the hand faces forwards. Movements of the
hand and fingers are defined from this position, movements of the forearm (radioulnar
joints) are defined from the fundamental reference position and movements at other
joints can be defined from either.
Planes and axes of movement
As we noted in Chapter 1, movements at the joints of the human musculoskeletal
system are mainly rotational and take place about a line perpendicular to the plane in
which they occur. This line is known as an axis of rotation. Three axes – the sagittal,
frontal and vertical (see also Box 1.2) – can be defined by the intersection of pairs of the
planes of movement as in Figure 1.2. These movements are specified in detail and
expanded upon in the next section.
Movements in the sagittal plane about the frontal axis
THE ANATOMY OF HUMAN MOVEMENT
Flexion, shown in Figure 1.3, is a movement away from the middle of the body in
which the angle between the two body segments decreases – a ‘bending’ movement.
The movement is usually to the anterior, except for the knee, ankle and toes. The
term hyperflexion is sometimes used to describe flexion of the upper arm beyond the
vertical. It is cumbersome and is completely unnecessary if the range of movement is
quantified.
Extension, also shown in Figure 1.3, is the return movement from flexion. Continuation
of extension beyond the reference position is known, anatomically, as
hyperextension. The return movement from a hyperextended position is usually
called flexion in sports biomechanics although, in strict anatomical terms, it is
described, somewhat cumbersomely, as reduction of hyperextension.
Dorsiflexion and plantar flexion are normally used to define sagittal plane movements
at the ankle joint. In dorsiflexion, the foot moves upwards towards the
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