Most of us understand that training results in a change in the direction of the training. If you have to walk uphill every day, your thighs and glutes adapt to the strain and become stronger. Your body adapts to the forces it encounters on a consistent basis.
If you train for a sport and that is the only training you put our body through, you create a bias. We improve at what we consistently do. This problem is apparent in athletes–especially young athletes. These athletes, like young trees, adapt to forces and are shaped by them. This can lead to a predisposition for injury. While the body is adapting in one direction it is not adapting in the other direction that is not being challenged. That is why soccer players are at risk for ACL tears and ballet dancers are prone to patellar tendonitis and knee problems, etc.
As humans, we like to do what is fun. How many of us spend time everyday on our weakness, physical or otherwise? Athletes are the same; they spend time focusing on the training and what will make them better at their sport. Little time is then spent on physical and structural weakness. It is taken for granted that the psoas, hamstrings, rotator cuff, anterior cervical musculature, etc. are strong because the rest of the body feels so strong. With such strength and ability, how can there be any weakness? I have seen it and believe that as we spend our time on skilled sport training without looking to part of that training for injury prevention, we are setting ourselves up for an injury.
Like the weak link in a chain, it takes just one time with just the right stresses, and we develop a limiting injury that prevents further normal function. That injury doesn’t come out of nowhere; we set it up by what we consistently do.