When we talk about sport we have to talk about the numbers as well. We all know that the “progressive overload” is the basic philosophy of any training system. We start with the athlete that doesn’t have any skills or knowledge and we gradually adding more "weight" so that athlete can adapt to it. Once athlete is adapted to that "weight" then we add more. It is a very simple concept and usually with young athletes we have a linear progression. The most important thing is that we don’t overload “too much” or “not enough”. We have to find that perfect middle. How do we do that? It’s simple, we have to measure the athlete’s capability. This is where qualitative and quantitative measuring come into play.
As a coach you want your athletes to perform movements fluidly and technically correct. If it looks ugly, then you need to make regressions either in the complexity of the exercise (range of motion) or the intensity (weight or speed). In these situations, quantitative feedback can sometimes be counterproductive because it encourages the athlete to push for speed or weight on top of a foundation of poor movement.
One scenario would be measuring the horizontal turn or change of direction. While change of direction can be a useful quantitative measurement it can come at the expense of movement quality. It is important to know which situations are conducive to measurement, and which ones are better for focusing on quality.
First and foremost it is important to work on the movement and technique. Once the technique is mastered then we can introduce external pressure or we can start measuring weight and speed. This is where quantitative measurements come in place. Quantitative measurements are very useful in the sense that they give us the precise picture of the athlete’s ability. With that information we can create plan where we will be certain that the athlete will be able to progress. This is where you find that sweet spot that will ensure proper development.