In the last issue we considered some of the adaptations that occur in horses during training. To recap, we know that improvements in cardiovascular and muscle function occur quite quickly after the onset of training. In fact, maximum aerobic capacity (VO2max) can increase by up to 10% after as little as two weeks of a regular exercise program. On the other hand, strengthening of the horse’s supporting structures (i.e., bone and tendon) occur much more slowly, and injury problems can develop if these structures are subjected to excessive overload too early in the training program. Thus, while the cardiovascular and energy-generating systems adapt quickly, we must design training programs that allow sufficient time for adaptation of supporting structures while at the same time provide the stimulus necessary for attainment of peak fitness. Training programs that provide a solid foundation of moderate intensity distance work before beginning any speed work will allow this goal to be realized.

To use this disciplined approach, we need methods for judging how hard the horse is working during training bouts. As well, it is useful to be able to measure improvements in fitness during a training program. By doing so, the speed or intensity of the workout can be stepped up in a controlled manner, helping reduce the risk of over-training or injury.

In laboratory settings, a large number of fitness parameters can be measured, but most of us do not have access to such facilities. Fortunately, much information can be gained by monitoring your horse’s heart rate. Heart rate is perhaps the best, and certainly the most practical, means for judging work effort during exercise. As we will discuss later, heart rate during exercise and recovery is a very useful guide to a horse’s progress during training.