. >> dr. joya specializes in treating concussions.e said a strong blow to the brain can change a child's brain chemistry. >> when we are concentrating, when we are thinking, remembering, when we are reading, when we are doing math problems, thing that is are required inschool, you are asking them to do a lot of work. >> he says a brain with the c concussi concussion, is like having a tired brain, it is hard to concentrate. if you stress it and overstress that brain that is not capable of doing the same amount of work that it can normally do, you are putting a greater burden on it. >> he started playing again. even after suffering from two concussions, he hopes to avoid a third. >> i'm excited to get back. >> dr. joya said there is no set standard when a child can miss school. most kids are given tests that can help determine how long the recovery time should be. childhood obesity is a problem throughout the name. the earlier children get active the less likely they will become overweight. morgan is 3 years old and loves to run, and pl