As coaches, we are in charge of lane placement. Whether it be during a specific set, for a particular practice, or for an entire season of training we have to decide which lanes the athletes will use. Lane placement can be decided based on a number of factors:
1. Each lane should have a leader. Move potential leaders into position based off this need. When lane leaders are homogeneous, the second swimmers in each lane will be homogeneous as well. Not only does this make for a more competitive environment, but it allows a coach to effectively manage the group. Consider the training set of 10x100 (120). If you have you entire first group swimming 1:05s, you can more effectively manage their set -- as oppossed to the situation when you have 3 swimmers swimming 1:05s, two swimmers swimming 1:08s, and one swimmer swimming 1:11s. In the less homogeneous situation, you have to wait until the 1:11 mark to teach effectively to each member of the first group. If each swimmer in your first group is swimming 1:05s, you can begin instruction to the entire group at 1:06, and by the time the second group comes in you'll be free to address them as needed.
2. Create groups based off gender sometimes. It's true that most competitive girls enjoy racing the boys -- they simply like the challenge...but they also don't always like to "beat" the other girls who are not only their teammates, but their classmates and friends. So it's good to let them race the boys. But as girls and get older, the boys generally improve at a faster rate. Even the most well-trained girls have an increasingly hard time staying up with the boys of the same performance level. We have to make sure in case that we separate the girls into "girls heats" and the boys into "boys heats". Certainly with the gender-based lane manipulation, what the answer is one day may not be the answer the next day. We have to figure out when it's appropriate to move people around, and when it's not.
3. Make sure you keep everyone mentally in the game. As a coach you have to watch for kids who are getting beat up everyday by the same people, or for kids who need a different type of challenge to achieve at a higher level. If you find either of these situations to be the case, find time to move the athlete around so they are in a different situation.