For centuries, people have trained race horses by making them pull heavy weights. But after Mehmet Kurt lost a horse due to overtraining, he decided to create a training vehicle that was safer and could be adjusted for individual training needs. Natalie Avon writes in Popular Science:
The horse isn’t pulling the four-and-a-half-ton, $427,000 vehicle. Rather, the vehicle keeps pace with the animal, and trainers fit the horse with equipment such as an electrocardiogram machine, oxygen masks and movement sensors to monitor its performance. They can then subtly regulate the horse’s speed for optimal training.
http://www.kurtsystems.com/index.htm via Popular Science