Dinamic visual acuity
If you are playing sport like racquetball, tennis, soccer or hockey, it is important that you be able to clearly see object while you and/or the object are moving fast. Without good dinamic visual acuity, you are going to have a difficult time in sports like these.
To improve dinamic visual acuity, cut different size letters out of a magazine and stick them on a stereo turntable and try to identify them (from about armīs lenght) at 33, 45 and 78 rpms. As it gets easier, use smaller letters.