horse - particular distance

Question
hello sir, how can a trainer decide that a horse requires a particular distance to race? for example, horse requires 6F race or 7F race?

Answer
The horse may be too slow to sprint a short distance but too fast and unratable to go a longer distance. Most horses should be able to go a mile unless mentally they will not pace. This is where the training comes in. Anyone can exercise and horse and training his body to do the work, but it takes a lot more to train a horse to run a race efficiently. Many horses have breathing problems too which would only allow them to run short distances. Some are too slow, but has the stamina to go long distances. The trainer will be able to evaluate what kind of athlete he as throughout the training process.