Introduction to Sports Biomechanics: Analysing Human Movement ...

INTRODUCTION TO SPORTS BIOMECHANICS
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equipment, this structure gives a material whose strength to weight ratio exceeds that of
either of its constituents.
With the exception of the articular surfaces, bones are wholly covered with a membrane
known as the periosteum. This has a strong outer layer of fibres of a protein,
collagen, and a deep layer that produces cells called osteoblasts, which participate in the
growth and repair of the bone. The periosteum also contains capillaries, which nourish
the bone, and it has a nerve supply. It is sensitive to injury and is the source of much of
the pain from fracture, bone bruises and shin splints. Muscles generally attach to the
periosteum, not directly to the bone, and the periosteum attaches to the bone by a series
of root-like processes.
Classification of bones
Bones can be classified according to their geometrical characteristics and functional
requirements, as follows.
The surface of a bone
Long bones occur mostly in the appendicular skeleton and function for weightbearing
and movement. They consist of a long, central shaft, known as the body
or diaphysis, the central cavity of which consists of the medullary canal, which is
filled with fatty yellow marrow. At the expanded ends of the bone, the compact
shell is very thin and the trabeculae are arranged along the lines of force transmission.
In the same region, the periosteum is replaced by smooth, hyaline articular
cartilage. This has no blood supply and is the residue of the cartilage from which
the bone formed. Examples of long bones are the humerus, radius and ulna of
the upper limb, the femur, tibia and fibula of the lower limb, and the phalanges
(Figure 6.5).
Short bones are composed of cancellous tissue and are irregular in shape, small,
chunky and roughly cubical; examples are the carpal bones of the hand and the
tarsal bones of the foot.
Flat bones are basically a sandwich of richly veined cancellous bone within two
layers of compact bone. They serve as extensive flat areas for muscle attachment and,
except for the scapulae, enclose body cavities. Examples are the sternum, ribs and
ilium.
Irregular bones are adapted to special purposes and include the vertebrae, sacrum,
coccyx, ischium and pubis.
Sesamoid bones form in certain tendons; the most important example is the patella
(the kneecap).
The surface of a bone is rich in markings that show its history; some examples are
shown in Figure 6.6. Some of these markings can be seen at the skin surface and many