Long Term Athletic Development
There have been a few studies that wanted to find out how much pre-pubescent kids were going to gain in strength by going through a strength training program. They took a control group of 10-12 year old boys and girls and they didn't do anything. They put a similar group through a strength training protocol of so many days per week and so many weeks. At the beginning and at the end they did strength tests to find out where the kids started from and the improvement at the end of the program. What they found is that the control group that didn't do any exercise and the group that did actually ended in the same place. They had the same increase in strength regardless of whether they did strength training or not. So it shows you that before puberty hits and testosterone courses through girls and boys, that they're going to naturally increase in their strength as they grow.
The real purpose for strength training of pre-pubescent youth is establishing proper foundations of discipline, movement, technique, mindset, and focus. It is a lot easier to train teenagers and young adults who have had background experience than those starting for the first time. Those who have not had that experience at a younger age are so far behind just starting out than those who have the experience. The central nervous system is neurologically more adept for those that have had that early training. Their body physiologically knows what to expect compared to those that have not trained before, and mentally they are also more prepared.
As a result, they are also more receptive to the skill training in their sport. We have prepared them by trainings foundational skills such as speed, mobility, stability and other elements, often based on their individual growth rates. Canada, Korea and some European countries have been doing Long Term Athletic Development (LTAD) for the past few decades. They start with children at a young age and chart their growth rate all the way through to adulthood and establish their type of training base on their growth velocity – when their spurts are, when they're slowing down. They know when to program in speed, when to program strength or skills or multi-directional movement (eye-hand coordination). When you look at the last winter Olympics the team that had the most medals was Canada. They always get a lot of winter Olympic medals, but have never led as they did in the last one. A lot of top professional golfers are coming out of Korea now.
Hockey is huge proponent of Long Term Athletic Development (LTAD). If you watch how the Canadian hockey world is developing their athletes you'll see that they are starting at young ages and determining when to train them at specific times based on when they're growing.