In all likelihood, if the load is too heavy, it will affect posture and may lead to serious back pain, with the effects possibly persisting in later life.
The issue of children as pack animals has been raised for decades by both parents and scientists. While more research on limits is needed, a consensus has arisen that to avoid back pain, the load should not exceed 10 to 15 percent of the child’s weight, according to a review article this year in The Journal of Clinical Chiropractic Pediatrics.
The risk of pain is especially high when the weight is carried on one shoulder, said the review, a survey of published studies. Even when a heavy load is evenly distributed, there is a tendency to lean forward to compensate for the weight.
In one small direct study, magnetic resonance imaging was used on healthy children carrying various weights. It found greater compression of the disks of the lower spine with increasing weight, as well as increased asymmetry of the disks. Significant pain was also reported.