There are multiple use cases for this type of warm-up. The first is to warm the players up for the activity that they are about to engage in. The second is by integrating this into normal youth club baseball rhythms (e.g., team practices and games), the kids are essentially getting speed instruction and training at every baseball practice/game without necessarily being cognizant of it. The third is that this will introduce new movement patterns which will make the kids better athletes and also prevent injury due to natural immobility baseball players get as they mature.