They're not sure why, but researchers have found that fit kids have stronger language skills. Researchers measured brain activity for aerobically fit and unfit children while reading both normal and jumbled sentences. The fit kids performed better on both sentences. While they can't prove fitness directly causes improved cognitive performance, it appears fit kids' brains may better allocate brain resources for reading.
PositiveTip: Keep your kids active, reading comprehension appears to be yet another benefit.