Harness dogs can start pulling from eight months old. Previously, they are educated to play a well-defined role. The leaders, in the pole position, are the smartest and most obedient ; they guide, give the impetus to the group and must strictly respect the instructions of the musher (sled driver). Next, come the swing dogs who assist the leaders whom they occasionally second. In the third row, the team dogs set the pace. Finally, the wheel dogs are the most powerful dogs in the team, they help the musher when starting and piloting the sled.