Gait and Gait Analysis

Travelling short or medium distances for us is easily accomplished by walking, which is convenient and easy but needs our muscles and joints to be in good condition and to be pain free. Having enough muscle power and sufficient joint range of movement in the legs is necessary for efficient walking. As walking progresses one leg gives the body support while the other swings through to be placed forward and in its turn to take weight. The swing and stance phases are the easiest way of understanding where either leg is at a particular point.

The process of going through all the stages and getting back onto the same foot again is known as the gait cycle. Both feet are down on the ground for about 10% of the gait cycle, with a single down on the ground for about 40% percent overall. The remainder is made up of the swing part of the cycle as the legs are being brought through to be placed down on the ground again for the next step. As walking gets faster the duration of these phases of the gait cycle reduces and when we start running then there is no double support phase when both legs are on the ground at the same time.

The stance and swing phases consist of a precise and repeatable series of movements during normal locomotion, with five different stages of stance phase. These are initial contact, loading response, mid stance, terminal stance and preswing, although initial contact is often referred to as heel strike. Heel strike is a slight misnomer as some people do not heel strike or at least weight transfer to the heel later in the phase. Heel strike allows shock reduction and maintenance of stability and speed whilst accomplishing weight transfer to a new leg.

The swing phase occurs as the other leg supports the weight of the body, taking the body centre of support to be placed over the foot in what is referred to as mid stance which initiates the phase of single leg support. The supporting foot lifts at the heel as the cycle progresses into terminal stance, a phase which stops when heel strike is obtained on the other foot. The swing phase is about to start and preswing consists of the last part of the double support phase before the leg goes on into swing. There are three swing phases, initial, mid and terminal, which allow the leg to be brought forward for the next heel strike and for the leg to clear the intervening ground.

Energy conservation and shock absorption are important parts of efficient gait. The joint contact forces can be increased if there are joint restrictions or loss of muscle power, leading to structural pathologies in the abnormally loaded areas. Sixty percent of the bodyweight loads extremely quickly onto the leg in the early stance phase, taking only twenty milliseconds.

The leg joints absorb and control these forces as they act as shock absorbers and dampers. When the leg is placed initially on the ground the forward forces involved tend to make the knee bend so we resist this by making the knee straighter even though this increases the forces through the joints. Loading forces are minimised by eccentric muscle action by the hip adductors and quadriceps.

Walking always takes energy but these demands are relatively small for normal adults walking on the level at their natural speed. We each tend to have a naturally chosen walking speed which minimises the amount of energy we expend. All muscular or neurological conditions slow walking speed down but do not necessarily increase the amount of energy used per time due to the slower cycle. Even though the energy cost per unit time may not change the actual cost of getting along a particular distance can increase markedly, for instance more than 3 times the normal in stroke.

Using a wheelchair cuts energy requirements per distance by 50% and allows speed to be maintained. The choice of using a wheelchair may be made by a patient when the amount of energy to get across a certain distance exceeds a certain level, often when the load exceeds 300% of what would be normally required.

Autor: Jonathan Blood-Smyth

Jonathan Blood Smyth is Superintendent of a large team of Physiotherapists at an NHS hospital in Devon. He specialises in orthopaedic conditions and looking after joint replacements as well as managing chronic pain. Visit the website he edits if you are looking for physiotherapists in Brighton or elsewhere in the UK.

Added: February 16, 2009
Source: http://ezinearticles.com/