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As riders we appreciate the importance of balance. We don't need sophisticated equipment to tell us whether a horse is moving on his forehand or on his haunches. What we can do in the laboratory, though, is measure exactly how much weight is being carried by the front and hind limbs. In this column we'll look at the influence of the position of the horse's head and neck on his balance in terms of the weight distribution on the front and hind limbs. In order to understand the mechanics of balance, it's convenient to divide the horse into several parts: the head, neck, trunk, front limbs and hind limbs. The trunk segment, which includes all the vertebrae, ribs and sternum, together with the contents of the thorax and abdomen, accounts for the majority (57%) of the horse's body weight. Each front limb is about 7% of the weight (14% for the two front limbs) and each hind limb is about 9.5% (19% for the two hind limbs). The hind limbs are heavier than the front limbs as a result of the large heavy muscles in the hindquarters, and this tends to shift more weight to the hindquarters. However, this does not take account of the head (4%) and neck (6%). Although they represent only 10% of the horse's weight, the position of the head and neck, sticking out in front of the body, gives them a relatively large influence on the horse's balance and weight distribution. The standing horse carries 55-60% of his weight on the front limbs and only 40-45% of his weight on the hind limbs.
 One of the objectives of dressage training is to change the horse's balance by shifting more weight onto the hindquarters which allows the forehand to become lighter and more mobile. When the trained horse carries himself in a collected outline, the hindquarters are lowered and the neck is elevated. On the way to achieving this, however, the horse will be worked in a lower, deeper frame. We were interested in finding out more about the effect of the head and neck position on the horse's balance and the study described below was designed as a first step in this process. This study involved measuring the effect of head and neck position on the weight distribution between the front and hind limbs. Of course, this is only one part of the balance equation, and there are other components that will need to be investigated later. The way the study was performed is that we took a group of six horses and weighed them to determine their total body weight. We then had them stand squarely, first with both front hooves on our force plat-e and then with both hind hooves on the force plate. The weight carried by the front limbs and the weight carried by the hind limbs was measured with the head and neck in three positions: in a neutral position, in a lowered position and in an elevated position. These positions are shown in the pictures. Several recordings were made for each horse in each position and average values were calculated. The results showed that with the head in the neutral position, the front limbs carried 58% of the horse's weight and the hind limbs carried 42%. When the head and neck were lowered, the weight on the front limbs increased to 60% and the weight on the hind limbs decreased to 40%. When the head and neck were elevated, the weight on the front limbs was reduced to 56% and the weight on the hind limbs increased to 44%. Therefore, the center of gravity moved closer to the front limbs when the head and neck were lowered and moved closer to the hind limbs when the head and neck were elevated. This is no great surprise, but it was interesting to actually measure the amount by which the horse shifted his weight. Interestingly, when the head and neck were raised, the horses had a natural tendency to sit a little on their haunches. Because we wanted to study the effect of head and neck movements in isolation, we had a helper to steady the hindquarters and try to maintain a consistent position of the rest of the horse's body, so that head and neck movements could be studied in isolation. This simple study proves that, without any doubt, the position of the head and neck influences the horse's weight distribution and the position of his center of gravity. Of course, when the horse is in motion and moving in a round deep frame or in an elevated, collected frame, other parts of his body will contribute to shifts in the location of the center of gravity, and these were not taken into account here. These movements will be the subject of future research projects.
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