RECOMMENDATIONS FOR YOUNG ATHLETES
I want to make clear what is the best training option for young athletes who want to jump higher, run faster, or improve any athletic ability. Any low quality vertical jump program can give beginner athletes a few inches in a month, because beginner athletes can see improvement doing just about anything. That is how many programs on the market survive. The goal should be to see immediate improvements but also to set the athlete up for more gains and less risk of injury throughout the entire athletic career.
Flexibility, strength, explosiveness, springiness, and coordination are the contributors to a vertical jump. However, strength is what either creates potential or limits for the contribution of the other abilities. For example, let's say Athlete A has great explosiveness given the fact that he can hang power snatch 55% of his max squat. If he can't even squat his body weight, his power is still far below what it needs to be for a good vertical jump. Let's say Athlete A also has great reactive ability. It won't do him much good, because his muscle-tendon complex is not even strong enough to absorb or put out much force.
Athlete A needs to make major strength improvements, which will likely lead to a reduction in the other abilities. And in the meantime he is at a high risk of injury. Athlete B is at the other end of the spectrum. He can squat 2.5 times his body weight but has poor explosiveness and reactive strength. He would need to spend time on plyometrics and explosive training to be able to utilize his strength for athletic movements. Athlete B though, is at a low risk of injury due to his strength and flexibility gained in the weight room.
So let's look at typical young athletes. Are they in the weight room doing squats or are they playing sports with friends? Obviously, they're playing sports, which are full of plyometric action. So they naturally develop more reactive strength than raw strength. They are also likely to develop inflexibility, muscle imbalances, and poor biomechanics, problems that can all be eliminated with strength training and simple stretching. But very few middle school kids are lifting and stretching.
Another very important thing to consider is that strength and flexibility are much easier to develop at a young age. The body has incredible ability to build muscle in response to training while it is still growing and developing. In 7th grade, I followed a ridiculous strength training schedule that I created in ignorance, and I didn't even do the exercises correctly. But I was young and on a growth spurt, so it just worked any way.
Given these facts, if you are a beginner athlete, you need to focus on getting strong and flexible. This is reflected in the evaluation process and training phases in the jump science training program. You don't have to eliminate plyometric and explosive training, but focus on strength. This applies to any beginner athlete, but it especially applies if you are still growing. Take advantage of your body's ability to build muscle. I honestly believe most athletes could get their max squat up to two times body weight at age 18 if they start lifting at 14. Why not do that? And do some simple stretching along the way. You will be completely prepared for any kind of advanced training and set up for incredible athletic gains for the rest of your career.