Trotting races are a specific form of races that involve horses moving with a specific gait, namely a trot, where the diagonally opposing legs move in unison.
These racers involve riders who sit in carriages, known in racing parlance as sulkies featuring two wheels and a light weight frame that is attached to a harness on the horse or pony. Because the race is run at a trot and because the horse has to carry a load which includes the jockey and the apparatus he sits in, it is a delicate balance between speed, stamina and restraint.
Horses are made to gallop and it takes a lot for the jockey to pull back on the reins and try to make sure that the horse does not bolt off into a gallop. If the horse does so, then it is disqualified.
As a result, if you watch these races, it is immediately apparent that the jockey sits back in his or her harness with legs braced and extended, pulling on the reins to ensure that the horse stays in a trot.
These races involve a great deal of tactics and strategy. It would be easy to just bolt off and hope for the best, but if a jockey over exerts the horse which has nothing left in the gas tank for the final push, then the whole affair would have been useless.
The horses and jockeys start out on a fixed line, but then converge into the apex and the bet race line. In doing so, the jockey must show skill in not hitting other sulkies and not spooking the horse by driving it too close to other competitors.
Even if a team starts out on the outer lane, they all converge on the run in and it often becomes a very close run affair as the horses start to pull on the reins. This is where the discipline of the jockey comes in, holding the horse to prevent it from hitting a gallop, while at the same time pushing for the fastest trot possible.