Maximum heart rate
HRmax stands for the highest number of heart beats per minute (bpm) during maximal physical exercise. It's individual and depends on age, hereditary factors, breed, gender and fitness level. It may also vary according to the sports discipline performed. HRmax expresses the intensity of an exercise.
There are many ways to figure out a horse’s HRmax. The most accurate way is to measure it clinically, usually on a treadmill or by carrying out an exercise test that a veterinarian supervises. You can also multiply the age of the horse by 0.9 and then subtract that figure from 223 to get a good working estimate of the horse’s maximum heart rate.