Faigenbaum and Myer, 2009 completed a literature review of youth involved in resistance training. As anyone in the field can observe, younger and younger children are weightlifting and more children are participating in sports. Resistance training should be used to prevent injury and enhance sport performance at that age- not the other way around.
It was determined that the two greatest factors leading to injury among youth was poor supervision or poor coaching with youth not emotionally responsible enough to follow instruction. Once these factors were accounted for, the overwhelming majority of injuries were removed. Further, youth injury in weight lifting is quite low. Among 8-14 year olds weight lifting the rate of injury was 0.7 per 1000. Among American football players of the same age group in was 4.3 per 1000. This indicates that weightlifting for young children is 6 times safer than American football.
The greatest injury reported among the 8-13 year olds was hand and foot injuries from dropping and pinching the weights (rather them placing them down and holding them correctly). Older youth (16-19) reported back injuries and strains as their most common complaint.
I have heard doctors tell parents that children shouldn’t lift more than 5lbs. When you consider that many toys weigh more than that, one wonders what the doctor is thinking. Children require supervision and technique must be reinforced but they can lift heavy, like anyone else.