A general definition of posture is 'the position of a person's body parts', the definition of good or optimal posture is, however, a little more specific. Good posture is the position of least stress, where a balance exists in both the length and strength of skeletal muscle. Posture matters because, when muscles become longer, shorter, weaker or tighter than they should be the balance is lost. This can lead not only to alterations in appearance and function but also to pain.

Although good posture covers the position of each segment of the body, we will concentrate initially on the neck. In 'optimal posture' the head is positioned centrally above the ribcage and the ears are in line with the shoulders (from a side view). This allows the vertebrae in the neck to be stacked neatly and evenly, sharing out the stresses and supporting the weight of a heavy head, which is approximately 10lb in weight.

When the neck and head are not correctly aligned the pressure on the discs is uneven and so damage can occur, bringing with it muscle spasm, disc degeneration, crepitus (grinding) and a range of other symptoms including headaches, neck pain and weakness or numbness in the arms and hands. From a side view the chin would be 'poking' forwards, the head would be positioned forwards and the neck would be out of its natural alignment. The structures which support the head and neck would now be under increased pressure as the weight of the head moves forwards away from the optimal 'posture line' these stresses multiply. As a result the muscles in the back of the neck become short, tight and overworked, whilst the muscles at the front become lengthened and weak. As a consequence of this increased workload the body protects itself by laying down connective tissue over the vertebrae in the base of the neck and upper back, which you may know as a 'dowager's hump'. With age we can add the risk of osteoporosis, especially in the smaller vertebrae of the neck and upper back, which can cause the weakened vertebrae to become wedge shaped, altering posture permanently.

So what can I do?

The good news for everyone receiving this is that we are already doing something. For most of us that means practising Pilates once a week (sometimes twice!) and performing neck, shoulder and upper back mobility and strengthening exercises, but what else can we do?

The answer is to think about posture for the other 167 hours a week, or at least for some of that time. Here are a few examples:

•When you drive, sit tall against the back rest, lift your sternum, tuck the chin slightly and relax the shoulders. Driving can be a very tense activity, especially if you're driving a long distance or are in heavy traffic, the shoulders sneak up under your ears and your chin will move forward, creating tension and spoiling good alignment.

•When you watch TV if possible sit in a chair where your feet are on the floor and your lower back is supported by a cushion. Sit in a tall position, shoulders relaxing back. Keep the chin softly nodded and jaw horizontal.

•If using a laptop or desktop monitor ensure it is high enough for you to look forwards at it rather than down. You may need to put it on some books to lift it closer to eye level, rather than allowing your head to move forwards and down towards it.

•Every time you pass a mirror or a shop window, have a sneaky look at your reflection and briefly check you are standing tall, shoulders back and down, sternum lifted, chin tucked in, eyes on the horizon.

Please note that if you have been diagnosed with osteopenia or osteoporosis it is ESSENTIAL that you not only attempt to maintain good posture but also AVOID trunk flexion exercises (curl ups, crunches, sit ups) as these can increase the risk of wedge fractures. In Seniors and Beginner/Intermediate classes we avoid trunk flexion exercises completely, but if you attend other classes a pelvic tilt would be a good alternative to use. In addition to this we can use safe exercises to 'load' or stress these areas in class to help improve and maintain bone density and muscle balance with the intention of achieving permanent, pain free good posture.