Here is a detailed description of how you should run. It concentrates on your leg action. I got sent a copy of it and I think it comes from brianmac.co.uk.
Middle Distance Running Technique Guidance on the running technique of the middle distance runner is provided in the form of a series of pictures and associated notes that highlight the main technical points. The foot strikes the ground below the centre of gravity (which is around the central area of the hips) The strike is slightly on the outside of the foot and from the ball of the foot to the mid-foot. There is then a role across and a dropping of the heel.
The leg’s role is supporting and driving. As the foot strikes the ground there is also some flexion in the knee. This should not be too excessive, so leg strength must be developed to ensure stability in and around the knee. There is also some movement around the hip girdle. This can be excessive, so strength exercises for the whole region, especially abdominal and lower back, are required. It is very important that this region is kept stable, thus giving a strong platform from which to drive. As the torso moves ahead of the foot, the drive is initiated and the achilles and calf are placed under great stress. It is therefore important that stretching and strengthening of this area be incorporated into training.
Muscle fibres in the calf respond to a reflex action as they are placed in near full stretch and contract quickly, thus apparently straightening the foot, forcing the athlete back up higher on their fore-foot. (This makes the foot a further lever, often forgotten by many runners). The foot “grips” the ground as the torso moves ahead, forcing the leg into full extension. Once again, strength and flexibility of the hamstrings are important. After the athlete has reached almost full stretch, a reflex action occurs in the muscle fibres of the hamstring, quickly shortening it and pulling the foot up off the ground. This allows the whole of the limb to swing back a bit further.
Hip mobility and the ability to stretch the quads at the front of the leg are also vitally important. The upper part of the leg is drawn forward by the action of the quads and hip flexors beginning to shorten. The foot continues on an upward curve, with the help of the contracting hamstring and the hinge effect of the knee joint. It swings into the gluteus maximus (backside), so shortening the lever and making it easier to bring forwards. The thigh continues forward and the swings upwards, the head of the foot drops from its high point and accelerates downwards and forwards. The knee reaches its high point, which is not quite as high as that of a sprinter (i.e. at an angle of around 90 degrees to the rear leg).
The foot ends its swing through at a point just ahead of the knee. The leg maintains a slight angle at the knee (the leg is not straight). Having reached its high point the thigh starts a downward swing; this initiates an acceleration of the foot backwards. The foot once again strikes the floor in a backward motion, adding to the athlete’s forward motion.
General Notes: There is a very slight “rolling” of the shoulders as the arms keep the body balanced with a pumping action The shoulder joint should be very supple so that as the arm swings through it do not pull them up too much The shoulder girdle and the hip girdle twist slightly in opposite directions, counter balancing each other The arms do not work to hard and work with the diagonally opposite leg The arm should swing loosely by the side and should be bent at around 90 degrees. As the arm swings back, there is little or no straightening Hands are held in a very relaxed “fist” with the thumb resting on the forefinger The thumb should be uppermost and the elbows hang close but comfortably into the side of the body The body is held upright with the back relaxed but straight with minimal forward lean.