When preparing a horse for athletic events and sporting activities, whatever the discipline or level of difficulty, an important consideration is finding the horse’s “ideal” body weight. This concept is well recognized in human athletics. For weight-bearing competitive sports like racewalking, running, and cross-country skiing, the amount of energy required to walk, run, or ski at any given speed is directly related to body weight. The higher the body weight, the greater the amount of energy required to move the body.

On the other hand, for individuals who are somewhat overweight, a reduction in body mass will provide a competitive advantage. For those athletes, a reasonable approach to enhance performance is a moderate reduction in body mass, particularly fat mass. Of course, it always is possible to get too much of a good thing–excessive loss of body weight actually can decrease performance ability because of loss of lean body mass (particularly muscle) and a lack of energy reserves. Thus, there is an “ideal” body weight and body composition (the relative quantities of lean and fat mass).

What about horses?

We first must recognize that it is the combined weight of the horse, rider, and tack that is important when considering the energy cost of the horse’s movement. The effect of weight carriage is plainly evident in Thoroughbred racing–in handicapped races, lead weights are added to the saddle of the better-performing horses in an attempt to “even” the playing field. There is an old racing adage that says: “Weight will stop a train.” This extra weight increases the amount of energy required to run and can make the difference between winning and losing.

Setting aside the issue of rider and tack weight, it also is likely that the weight of the horse can influence performance. One of the current controversies surrounding the use of Lasix (furosemide)̵