I was not aware of this until I started searching for this information myself. You are right, there are differing opinions about children running marathons.

Our human body has evolved over many millions of years into good walkers and runners. Our legs, ankles, and feet, are well adapted to these activities. With their ability to run, early humans were able to hunt and capture animals for food. Running has been part of human existence and survival for a very long time.

However, long-distance running as a sport, like the marathon, is a relatively recent phenomenon, and it has become very popular in the last few decades. There are many marathons in North America and around the world. Most of the runners are adults, and there are quite a few seniors. Some marathons require the runners to be 18 years of age before they can participate, while others have no age limit as long as parents give their children permission to enter the race.

There have been no large scale research investigating the safety of long-distance running in children. We also don’t know whether there is any long term harmful effects on their growing bodies. There are individual testimonies proclaiming that long-distance running is totally safe and should be encouraged. However, many physicians and scientists tend to take a more conservative stance and advice caution. Even though there is no conclusive evidence that excessive running can cause long-term injury or damage to the developing bones, joints, cartilage, and ligaments, it is prudent to be cautious.

In addition to the physical demand of running, marathon is very much a mind game. There will be times when fatigue sets in, and the runner’s determination becomes the main driving force to keep going to the finish line. Many talks about marathon running as a personal challenge. The majority of young children do not have that degree of maturity when their body is exhausted.

It is useful to talk to your daughter to see how serious she is about marathon running, whether she understands the distance it covers (42.2 km), and that it will take many hours to complete. It is not a simple matter of fitness, it is the endurance of the body as well as the mind.

If she is really interested, it would be important that she has proper training. You may want to enlist a coach who has experience in training young athletes like her. It is important to find one who is not interested in pushing young children to run faster and longer. Excessive training without adequate rest and support can lead to serious injury. Proper footwear as well as clothing are also very important.

If you are a runner yourself, you can take her along with you, adjust your pace and gradually increase the distance to train her endurance. If she is out of breath, it is important to stop. If she has pain anywhere, she has to stop also. Running while injured is unsafe and may lead to more serious injury. You may want your family doctor to check her to make sure that she is physically fit to run long-distance.

It may be a good idea to sign her up for shorter runs to let her get a taste of it and to see how much she enjoys it. Many schools have track meets in the fall as well as the spring. Help her to train for these meets and gauge her interest. Afterwards, you can help her to enroll in 5K and 10K runs in your community. She can gradually build up her distance and her stamina. This would be a much better plan than go directly to a marathon.

There is no question that it is good for children to run. We want to encourage our children to be active: walking, running, skipping, skating, skiing, dancing, as well as many other organized or unorganized activities. Simply playing outside is far better than sitting indoors and watching TV, texting, going on Facebook, or exercising the thumbs on videogames. With the rising prevalence of overweight and obese children, we need to encourage all of them to be active, one way or another.

I hope these suggestions are sensible, in view of the lack of good scientific evidence on this subject.