https://www.youtube.com/watch?v=TMRVKPVtrQE
It takes some time to develop a real good crossover step. But once you do, we are talking about a tenth of a second advantage over back foot push. Truth is most every great base stealer uses the crossover. Even guys like Ricky Henderson who would often use the front foot movement as a timing device. Watch the video above or watch the top guys like Billy Hamilton.
Now, anytime the laser is being used, it becomes even more important to master a good crossover. Think about the start line... time starts when you cross that start line with any part of your body. So if you push off with your back foot and move your front foot forward, the clock starts when that front foot crosses the start line. If you push off with you front foot the clock doesn't start until some other part of the body crosses the start line.
3and2,
If your son can run 1,6 pushing off his back foot, he will run 1.5 if he masters the crossover. especially if he masters the best starting technique. You are simply able to gain more distance in the same amount of time. The thing many runners screw up is "accuracy". Think of your belly button being an arrow or your in a narrow tunnel from start to finish and you need to avoid hitting the walls. So when it (belly button) turns towards the target it immediately aligns with the target and stays on target. Then think of power and efficiency... many crossover with their left arm/hand moving forward with their left foot crossing over. This is something that has been taught for many years and it can create problems with balance, power and efficiency. Most every runners arm action is opposite arm stroke with each stride. It would feel strange to stride with your right leg while using a forward stroke with your right arm. So why would anyone want to start and be out of position immediately with left foot and left arm leading the way. Just think how much better position a runner would be in if the left foot and right arm worked together at the start. Now everything in your first stride after crossover is in proper running position. so you not only gain distance, you also reach top speed quicker because there is no adjustment required.
The key is to be accurate and balanced... everything else requires an adjustment. Good athletes don't always notice they are having to make an adjustment, they just automatically make the necessary adjustment. However, those adjustments, no matter how small, are actually taking time to make.
My guess is that your son has always used a certain way of pushing off and is more comfortable doing that. The crossover done properly will lower his times. Many use what is called a false step. this is when the front foot actually moves slightly backward in the first movement to gain power, early speed! That is OK but once again needs to be mastered.
I could go on for ever about this stuff, but don't have the time or energy to go much farther than this. Back when we did the running manual I worked closely with some of the best sprint coaches in the world. Those that coached Olympic sprinters like Carl Lewis and others. I never realized how much was involved before that. Everything from breathing, to using imagination, to visualization, to maintaining looseness. How running hard and running fast are often two completely different things. Anyway, since then we have never worked with any runner that didn't end up cutting at least 2 tenths out of their 60 time, some much more.
