We deal with this question over and over again, "Is it safe for young athletes to lift weights?"
Emphatically, YES!!! When it is properly performed. Should any young athlete take a max effort lift, NO. But they should learn proper motor patterns and strengthen their posterior chain and create great trunk stability (core for those of you waiting for that word). All these things will happen with light weights so that they can create a more efficient nervous system and have an immediate feedback loop for proper movement.
What I don't hear is "is it safe for my son to jump up in the air and land?" or "is it safe to do sit ups with feet anchored?" For some reason people have a fear of any weight like a dumbbell or kettle bell, yet they have no issue putting their child in pads and letting them ram full speed into another child. Those forces are up to 5x the child's bodyweight but that doesn't seem to bother parents. Or they have an issue with a 10lb kettle bell but the fact that the kid gets up each morning and grabs a gallon of milk out of the fridge, which weights 8lbs, doesn't seem to bother them.
Or that the kid is fine to jump off the swings at school, drop from the monkey bars, and jump out of trees. These things, while none of them are dangerous put an immense amount of force (far greater than any goblet squat) on the knees, ankles, and back. The list of examples are endless. I believe that none of these are inherently dangerous, unless you jump out of a 50ft tall tree or some other extreme example. Just like lifting weights for young athletes teaches and strengthens, unless you take it to the extreme and try to max little kids out, which is as stupid as jumping out of a 50ft tree.
At The Spot Athletics we teach proper form and progress athletes slowly so that they learn the proper way to do things. Does this mean that every rep is done 100% how it should, NO. I've been doing this for 20 years and I still don't do every rep correct. Kids have low attention spans and this is why they use light weights until they possess the requisite attention span and skill level to use heavier weights.
But let's talk about what heavy is. Heavy is relative and not absolute. For me a 500lb. squat is very light because I can do it for 15 reps. I doubt that would be light for any of our parents but they don't seem to come in with this understanding. Kids parents want to put a magical number on what is heavy. It is light if a kid can do it for 15 reps, no matter what the weight is. If Timmy does 100lbs. for 15 reps, it is light for him. It doesn't matter that it is 100lbs.
I am working on an educational series for parents because I really get sick of having these same conversations, over and over again. The fact is it is my job to educate the parents and if I have to answer this question then we have failed in educating the parents if they have been in our facility for at least a month. I know that we will not convince every parent that our way is the safest and best way for their kids to train, but I am going to try because if I have to hear one more parent ask for more running drills to work on their kids "speed" I'm going to kill myself.