Yao is at the crossroads of making a decision now. Do I let it heal by itself, or do I try another method? Rest is the healer. If you keep disrupting the healing, by constantly putting the same load and stress on the foot, it is not going to heal.
Yao has had bone fractures in the past. Are some people more prone to getting fractures?
They are. One reason could be foot mechanics. Is he a flatfoot? Does he have a higher arch? Does he have maybe a short leg and a long leg? If you upset the mechanics, you can concentrate the stress in a way that it is not normally focused. These are things we look at to explain why people that are healthy and built to play these sports keep getting hurt.
Another thing is that Yao is seven feet, six inches [2.28 meters] and has a foot size of 18. That is a small foot for someone so tall, so the pressure his body exerts is distributed over less area. We have players at Temple that are a foot shorter than him and wear a size 20.
Presumably, Yao would be forced to retire if he kept getting fractures or the fracture never heals properly. So how did he most likely injure his foot?
I have a general observation that people may be under the assumption that this is something you might get from jumping. Yao has over a two-foot- [60-centimeter-] high vertical leap. Yet it is not so much causing injuries as the running up and down the court. Due to the soft tissue of the foot and the nature of the arch, there is not as much impact coming down from a layup shot as there is running up and down the court.
What are the risks for everyday or recreational athletes?
Runners tend to develop more stress fractures than walkers. In running there is a flight phase where you are off the ground with both feet and landing on one foot.
We have the rule of three: three times your body weight on impact. So, if you are 100 pounds [45 kilograms], you are hitting the ground with 300 pounds [135 kilograms] of force. A walker always has one foot on the ground; therefore, the force is divided between legs, and only 1.5 times the body weight goes to a foot.
Overdoing it is the high risk. You know when training for a marathon you can only run 100-mile weeks for so long before the osteoclast cells begin acting. The bones are constantly remodeling to adapt to the stress and get to the point where the osteoblast cells cannot keep up with the osteoclast cells, which are removing bone tissue.
Yao reportedly is feeling no symptoms and has no physical signs from the fracture. Is it possible a person might not know if they have a fracture?
Yao is probably not training. The minute he would go back and train he would feel it. You cannot play through it. In other words, something like tendonitis starts to feel better after you warm up and while you play, but a stress fracture does not get better. It gets worse.