You can do core training at any age,, But weight training should not start until high school.

i totally agree with u, u shouldnt start weighing some weights until ur older!

Youngsters, especially pre-teens are not physically ready to tackle weight training. In fact the training could most likely cause more harm than good. Endurance training and basic core exercises will help him develop until he gets into high school. Then he needs to decide if he's going to train for football or baseball. Football, for the most part, is based on bursts of speed and bulk strength. In baseball you don't want the bulk because it can hamper the mechanics. For baseball you want reps not higher weights. Football, especially depending on his position, he may want to build up bulk with greater weights.

Put him in swimming, that will give him a jump start on his lungs and heart and the
rest of his body. This will give him balance for the strength traing later. Speed and
endurance will also be there, no heavie weights are needed till he hits high school
or you run the risk of stunting his growth potential.

weight training at age 10 is appropriate so long as it is light weight and high reps and not power lifting. The old studies on stunting grown were done on powerlifters in the eastern block and isn't an issues. The window for strength development in Youth starts to open at age 8 but isn't significant until age 12. But the will to learn also closes from ages 12 to 16. If you start weight training at a young age you do it with the focus on technique and habit not on max weight youth of that age shouldn't be lifting for max. The can do high reps of low weight and really get a head start on other kids. Before the age of 10 the window for Flexibility is very large should be focused on. The window for speed is widest between the ages of 7 and 12.

i would wait to do weight training until the 7th or 8th grade.

his to young

he should start weight training when hes 10 as long as its not power lifting
if hes a tough guy start with 3-5lb dumbbells if he not that tough start of with
2-3lb dumbbells well im thinking hes tough so if i were you ill start of him with 5lbdumbells/weights if he does a lot of sports or carry stuff alot

First of all, you need to prepare his body for lifting heavy weight, which you can start at almost any age, but until he is closer to high school (13ish), you MUST consult a physical therapist before starting him on any type of heavy lifting. Needless to say, asking people via the internet is not the smartest way to get answers to hard questions.. Especially when it concerns your son's physical well being.

That having been said, at age 9, lifting weights would be much too advanced for him. Although, do not underestimate the power of Calisthetics-- the use of body weight to increase strength and endurance --such as push-ups, pulls ups, dips, sit-ups, frog jumps, wall sits, etc-- to build up his strength, as well as his aerobic system, diaphragm(lung) power, his adrenaline glands.
After starting him on a daily (3-5x/wk) Calisthetics/ Circuit program, vary the intensity (fast repititions versus slow and controlled) and progress towards the weight room after a few months of monitoring him. You will be able to determine how much progress he has made very quickly I believe, and you can start introducing him to the weight room after maybe just 4 months.
BUT WORK WITH ENDURANCE FIRST, like others have already stated.
High repetitions, lower weights--- aim for a minimum of 10 repetitions for each set, preferably closer to 15.
Every 4 months, evaluate his progress. I would not start him on heavy lifting, instead you should play with the intensity of the workout. To provide some examples: Reduce the rest period between each set or between each exercise, working out 3 days this week and 5 days next week, 3 exercises Monday, 6 on Wed.

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