Introduction to Sports Biomechanics: Analysing Human Movement ...

INTRODUCTION TO SPORTS BIOMECHANICS
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omitted or abbreviated to m or M., followed by adjectives or genitives of nouns. The
name may refer to role, location, size or shape of the muscle. An example of a muscle
named after its location is the latissimus dorsi – the broadest (latissimus) muscle of the
back. The flexor digitorum profundus is named after its role – the deep (profundus)
flexor of the fingers. The trapezius muscle – the English name is identical to the Latin
one for this, but for only a few other, muscles – is named after its trapezoidal shape.
Some English names have become accepted, such as the anterior deltoid; obvious
English translations of the Latin names, for example the deep flexor of the fingers
(see above) are – somewhat sadly in my view – not commonly encountered in most
scientific literature.
Muscles are often described by their role, such as the flexors of the knee and the
abductors of the humerus. Most muscles have more than one role in movement; multijoint
muscles have roles at more than one joint.
Structural classification of muscles
The internal structure or arrangement of the muscle fascicles is related to both the
force of contraction and the range of movement and, therefore, serves as a logical
way of classifying muscles. There are two basic types each of which is further
subdivided.
Collinear muscles (Figures 6.9(a) to (e)) have muscle fascicles that are more or less
parallel. A collinear muscle is capable of shortening by about one-third to one-half of its
belly’s length. Such muscles have a large range of movement, which is limited by the
fraction of the muscle length that is tendinous. These muscles are very common in the
extremities and are further divided as follows.
Longitudinal muscles consist of long, strap-like fascicles parallel to the long axis, as
shown schematically in Figure 6.9(a); examples are the rectus abdominis muscle of
the abdominal wall and the sartorius, the longest muscle in the human body, which
crosses the hip and knee joints across the front of the thigh.
Quadrate muscles are four-sided, usually flat, with parallel fascicles, as in Figures
6.9(b) and (c). They may have a rhomboid shape as in the schematic representation
of the rhomboideus major – a muscle of the scapula – in Figure 6.9(b), or
rectangular, as, for example, the pronator quadratus, located on the anterior aspect
of the forearm near the wrist and shown schematically in Figure 6.9(c).
Fan-shaped muscles (Figure 6.9(d)) are relatively flat with almost parallel fascicles
that converge towards the insertion point. A good example is the pectoralis major
muscle on the upper anterior surface of the trunk.
Fusiform muscles are usually rounded, tapering at either end (Figure 6.9(e)), and
include the elbow flexors: brachialis, brachioradialis and biceps brachii. The location
of the last of these is certainly familiar to most, if not all, sport and exercise science
students. The brachialis lies directly underneath the biceps brachii, is a single joint
muscle and is the main elbow flexor.