Ever wondered what holds your body together? And how the skeleton works and how it’s held together? It all starts with bones, tendons and ligaments.
A baby is born with 300 bones while an adult has only 206 bones. This is because certain bones, particularly those in the skull
and spine, fuse together as the child grows. The smallest bone in the body is the stirrup bone in the ear which is just 3mm long.
The longest and strongest bone is the femur, or thighbone, which makes up about a quarter of a person's height.
At each end of every muscle, the covering of the muscle tapers to form a strong, rope-like length of specialised muscle called a tendon
which, in turn, is connected directly to a bone. The end of the muscle which connects to the relatively unmoving skeletal part is known
as the “origin” of the muscle. The point of attachment to a moving bone is known as the "insertion" of the muscle.
When a muscle contracts, the origin and insertion are pulled closer together, often across a joint. This contraction creates
movement of the joint, allowing the pushing and pulling that make up physical movement.
Often this movement involves a shortening of the involved muscles. This is called a concentric contraction eg. lifting a heavy weight
off the ground. If the opposing force is greater than the muscle force, however, the muscle may actually lengthen as it works to
contract. For example, when you lower a heavy weight down to the floor, your bicep muscle lengthens even though it is tensing. This
is called an eccentric contraction. If, however, the muscle does not change length at all during the contraction, the result is an isometric
contraction e.g. when you push against a stationary wall.
Other types of connective tissue also help to create smooth, controlled movements. Ligaments are tough, stretchable bands that connect the bones
together and help stabilise a joint. Ligaments help guide how the bones move in relation to each other. Nerve receptors in the ligaments and
tendons send information to the brain to help regulate the intensity of muscle contractions and to help avoid injury. For example, if a joint
is extended to its maximum, a signal is transmitted to the brain to avoid any further extension. A fluid-filled sac, called a bursa, cushions
and lubricates the tendons and other tissues sliding across the larger joints such as the hips, knees and shoulders.
Because tendons, ligaments, and bursae take longer to adapt to physical activity than muscle fibres do, these connective tissues are particularly
vulnerable to inflammation and tearing, especially from any type of repeated movement. For this reason, bursitis (inflammation of a bursa),
tendonitis (inflammation of a tendon) and ligament injuries are common overuse problems after prolonged, repetitive activities, such as long
distance running, cycling or even prolonged typing at a computer.
Keeping the bones of the body in a healthy, fit condition through regular exercise is one of the keys to maintaining a lifetime of health and wellbeing.