Joints

All of the bones, except the hyoid bone in the neck, form a joint. Joints are often categorised by the amount of motion they allow. Some of the joints are fixed, like those in the skull, allow for no movement. Other joints, like those between the vertebrae of the spine, allow for some movement. Most of the joints are free moving synovial joints.

Ball and Socket Joint

This type of joint allows for a wide range of rotation and movement. The shoulder and hip are ball and socket joints.

Condyloid Joint

This type of joint allows movement but no rotation. There are condyloid joints in the jaw and fingers.

Gliding Joint

This type of joint allows bones to glide past each other. There are gliding joints in your ankles, wrists and spine.

Hinge Joint

This type of joint allows for movement much like that of a door hinge. The patella and ulna part of the elbow are hinge joints.

Pivot Joint

This type of joint allows bones to spin and twist around other bones. There are pivot joints in the neck and the radius part of the elbow.

Saddle Joint

This type of joint allows for back and forth and side to side motion but limited rotation. There is a saddle joint in the thumb.

Range of motion

Defined as 'the measurement of the extent to which a joint can go through all of its normal spectrum of movement'.

Range of motion can also be used to describe the existing amount of motion around a joint. For example, if a cyclist who rides 100 miles or more per week doesn't stretch regularly, he or she might experience limited motion at the hip joint. The term 'range of motion' could be used to refer to this measurement.

Another example would be a person who sits at the computer all day. Such a person is likely to have tight muscles at the front of the shoulder joint, and overstretched muscles in the upper back. This imbalance in muscle tone will probably alter that person's range of motion at the shoulder.

Range of motion is expressed in degrees of joint angle or circumference (depending upon what type of joint is being measured). Each joint has an established normal range, based on what that joint does and where the two bones comprising it can move no more. In other words, the normal range of movement is determined by the architecture of the bones and the soft tissues that surround the joint to hold it together. Range of motion is related to flexibility. (Asher, 2011)

What are body mechanics?

In the Major Study Performance component of your HSC it is a requirement to further your knowledge and learn about fundamental body mechanics in relation to the dancing body, body systems such as respiration and circulation, kinaesthetic awareness in order to realise efficiency and aesthetics.

Body mechanics is the coordinated efforts of the musculoskeletal and nervous systems to maintain balance, posture and body alignment.

Good body mechanics are essential to move efficiently and to defend against the possibility of injury. Body mechanics is the functional relationship among the various body parts.

Good body mechanics is relative to the type of activity being engaged in, such as floor work, barre work, centre work, moving in space and jumps and aerial work, as well as the somatotype that the individual is endowed with. To maintain proper alignment, the human body must continually combat the force of gravity as it is being pulled toward the centre of the earth. Body segments such the hip and knee that are misaligned react to gravity more adversely than segments that are in good alignment.

The human skeletal system is a complex, dynamic structure. Joints are capable of an enormous amount of motion and the flexibility of the spine multiplies the joints capabilities. Understanding the intricacies of body mechanics takes a lot of work.

Body mechanics pertain to the position of your body when it's moving. Proper body mechanics are important for everyone and especially for people with arthritis or other musculoskeletal conditions. Correct body position can help:

• relieve pain
• reduce stress on joints
• reduce the risk of injury.

With every movement, as you stand, sit, walk, drive, lift, reach, push, pull, exercise, and even sleep, it's important to be aware of your body position. If you can improve your posture when moving, you are essentially protecting your joints.

How do proper body mechanics protect joints?

Proper body mechanics and specifically proper posture can:

• align bones and joints
• reduce wear and tear on joints
• reduce stress on supporting structures (e.g., ligaments) and joints
• strengthen the spine
• strengthen muscles
• prevent muscle pain
• conserve energy.

Movements that incorporate good posture and good body mechanics will help conserve energy. Walking builds muscle strength that in turn helps to protect joints. There is a right way and a wrong way to move. Your body will be healthier and joints will be protected if you make a conscious effort to move the right way. (Eustice, 2007)