[FF30X FAQ] Can my 10 year old son lift weights with me?

Question: Can my 10-year old son start lifting weights with me on the FF30X program?  I have heard lifting weights can stunt a child’s growth. Is it safe for a 10-year old boy/girl to lift weights?

Answer:
Short answer: Safe and effective weight training has been documented with children as young as 6 years of age.
There is an old misconception that weight training can hurt a child’s growth plate in their bones, thus impairing the full development of the bone. While there is some truth in your concern, I label it a misconception because when statistics are reviewed the chances of your child hurting their growth plates playing soccer, gymnastics, or other sports is drastically higher than weight training.
While growth plate injuries have been recorded with weight training they are rare and almost always, linked to a poorly established program or one that is not supervised. All too often kids are in a weight room and mimicking what they see the other kids doing or what the coach, who has a beer belly, no knowledge of exercise science, and has not touched a weight since high school in 1947, tells them to do. 
This  leads to kids lifting weight that is too heavy and doing so with improper form, which are two ingredients for injury by placing too much stress on the body. Also with lack of supervision, a weight room invites horseplay during lifting which also leads to these injuries.
Thankfully, a properly established and supervised weight-training program will help both boys and girls in a number of ways. A few of the documented benefits include increased strength, speed, and agility along with improved coordination and self-esteem. Weight training will certainly increase your child’s sports performance considerably while decreasing their exposure to injury.
Another thing I would like to point out is that if your child learns proper lifting form at age 10, he or she will go through life with proper lifting mechanics which will not only decrease concerns of growth-plate injuries but also help him/her add muscle mass as the proper lifting technique will both be safe and provide the maximal results.
As this background info relates to your son/daughter doing FF30X:
The Apex10 workout in FF30X Phase #1 is a perfect place for your children to start training as all of the exercises involve lighter dumbbells not directly loaded on the spine.
I would like to re-emphasize this point: form is incredibly important. It's essential to make sure your son/daughter is learning the right movement patterns on his pushups, squats, presses, and rows. With proper guidance on form and a light enough weight, your son/daughter will likely experience an increase in strength, speed, flexibility, and overall confidence form following these workouts 2-3x/week.
Research Cited:

Position statement on youth resistance training: the 2014 International Consensus.
https://www.ncbi.nlm.nih.gov/pubmed/24055781

“I have no idea where these myths started, but the evidence is clear: It is absolutely safe for kids to start lifting weights early in life, provided they do so under a well-designed, supervised program,” says Gregory Myer, Ph.D., director of research and The Human Performance Laboratory for the Division of Sports Medicine at Cincinnati Children’s Hospital Medical Center."