Impact of Distance Changes on Horse Fitness: A Trainer's Perspective

Question
hello sir, if a trainer races his horse at long distance like 1800m once and then gives a next run at short distance like 1000m, does the horse become weak and thin?

Answer
I see no reason to think this to be true based on the change in distance. I have never experienced this although if a trainer is not feeding his horses properly or managing ulcers or other health concerns, a horse may lose more weight than normal when under the stress of training and racing. A fit and healthy horse should be able to run back that shorter distance without a problem as long as he has recovered physically from his last race. A good trainer should be able tell when the horse is ready to run back or needs more time for energy and weight gain.