the riders were all thin and wiry-looking and the horses were all much smaller than the standard western breeds and the speed of the horses and the agility of the men was often breathtaking ; the riders literally stood in their stirrups whenever their ponies were in motion and , with the reins in one hand and with a long bamboo pole with a loop of rope on the end in the other , they would charge into the herd and try to cut out a particularly good-looking animal by placing the rope over its head and around its neck and bringing it to a standstill by exerting pressure on the rope and pole as the riders own mount obviously well-trained for the job and responding to the slightest shift in the riders weight swerved and attempted to slow down once the loop had settled around the other ponys neck .