Physiotherapy 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.
Achieving all the phases of gait so that you get back onto the same foot you started on is referred to as the gait cycle. The duration of both feet remaining on the ground at the same time is about 10 percent and one leg is standing on the ground for about 40 percent of the time. The rest consists of the swing part of the cycle as the non-weightbearing leg is taken through to a position where it can again bear weight. As our walking speeds increase the duration of the gait cycle phases reduces until there is no double support phase where both feet are weight bearing at the same time, a condition known as running.
The leg joints follow a specific and repeatable series of actions during the swing and stance phases with stance made up of five sections in the order of initial contact, loading response, mid stance, terminal stance and preswing. Heel strike is the common name given to initial contact but some people do not heel strike at all or transfer weight to the heel later in the phase. Heel strike allows the leg which is about to weight bear to take the weight but not compromise speed, stability or shock protection.
While the one leg is supporting the weight of the body the other leg is in swing phase. The first part of the single leg support phase is called mid stance and it is during this phase that the bodyweight moves the centre of gravity and support over the foot. The cycle continues into terminal stance where the supporting foot rises at the heel and then stops when the opposite foot makes contact. The last phase, which is preswing, is preparatory for the swing phase, starting with the last part of both leg support and ending when the heel comes up on one side. The swing phases (initial, mid and terminal) manage clearance of the foot above the ground and the bringing forward of the trailing limb to move to the front.
Efficient gait includes aspects of shock absorption and energy conservation and alterations of joint movement or absence of muscle power may increase the joint contact forces which can lead to pathological changes in the structures abnormally loaded. Almost 60% of the body weight is transferred to the early stance leg in very short period, under 20 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.
Locomotion demands that we expend energy but for most of us the level is low if we are healthy, going at our normal speed and walking on level ground. We minimise the amount of energy we use in walking by choosing a preferred speed which is most efficient. Musculoskeletal or neurological conditions always slow down the walking speed but do not have to increase the energy load per unit time because patients usually slow their cycle down. However, the energy needed to cover an identified distance can increase greatly with more than three times the normal expenditure in the case of stroke.
Wheelchair use allows locomotion speed to be maintained and can cut energy expenditure per unit of distance by fifty percent. Patients tend to choose a wheelchair to get about when the amount of energy necessary exceeds a particular level, especially when it goes beyond three times the normal amount of energy required.
About the Author
Jonathan Blood Smyth is a Superintendent of Physiotherapy at an NHS hospital in the South-West of the UK. 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 Manchester.
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