Earlier this year we purchased our second set of expensive orthotics for my 12 y/o daughter who has significant arch problems and used to barely be able to walk after soccer games. She tells me "a girl has to have shoes" therefore they are constantly lost because we couldn't afford to get multiple sets.
My son, who is currently a freshman on the HS cross country team had been complaining of major pain in his right calf/soleus, which eventually moved into knee pain and now lower back pain. This wasn't a problem early on, but once the pain started to migrate up a familiar path, we knew we needed to address his flat feet issues quickly and really nice (expensive) running shoes were only part of the solution.
We rushed to get him a pair of the M100 for his running shoes, and the T100 for his daily school shoes. He didn't have time to slowly work them in as the product recommended and although he wore them around the house the night we got them, he put them right to work this week for a 9 mile run the following day.
He said for the first time, he didn't feel like his legs and feet were going to come apart at the joints. No back pain after the run, one calf muscle actually stopped hurting halfway through the run, and he was able to take around 5 minutes off a previous 9-mile time.
For a kid that has logged nearly 600 miles and 3 pairs of shoes in the last 6 months, we wish we would have known about these a long time ago. It would be an interesting study to see what kind of improvement these could make for an entire cross country team, both for reduction of injuries/pain and prolonging shoe life.