Sticking with two wheels, we move on to the noisy but highly entertaining sport of motorcycle trials, with this shot from Heath Brindley of Weston-Super-Mare, UK. Heath has used a powerful flash to freeze the action, catching the intent concentration on the rider's face.
Keeping on with the theme of motorcycles, I thought this shot from John Seymour of Amersham in Buckinghamshire, UK, must be Photoshopped, but he assures me that it isn't. Not that it would have mattered, since edited photos are allowed anyway, but I love the reflection in the helmet visor.
Skateboarding was another popular subject, with several very good entries. The best of the bunch was this ultra-wide-angle shot from Mikk TÃµnissoo of Saue in Estonia. I suspect that Mikk has used a wide-angle adapter to produce the fish-eye effect.