Well that's an old wives tale, no Studies have ever been shown that lifting weights stunts or inhibits growth. So stop listening to They because they don't know crap!!
They say that kids should not lift something that is very heavy, as it could cause back injury or stunted growth. Would lifting something very heavy just one time be safe? Or will that result in injury to the kid?
That old yarn is more to protect children from serious injury. Lifting heavy items safely involves a certain amount of care, strength and technique.
It isn’t reasonable to expect children to know these things. It isn’t worth the worst case scenario coming to fruition.
Kids as well as adults should use their legs instead of their backs to lift heavy objects. An injury is a possibility but not a guarantee from lifting the wrong way . I've never heard of stunted growth from lifting heavy objects.
Lifting something heavy will not stunt growth. Lifting something that is heavy can injure people of any age if not done properly. Depending on the age and coordination of the child lifting can be done safely. I wouldn't expect a toddler to safely lift anything of any significant weight. A preteen on the other hand could within reason.