Karate dojo

Camera Olympus E-510  f/4, 1/250, ISO 800

Ok, this week was difficult... The occasion was very nice: the karate exam in my dojo. But, the conditions to make the photo were not very easy to handle: very low light and people moving fast. I was obliged to shoot at 800 iso all the time. In this picture I really like the subject and the composition, but the lightning is very bad...
Suggestions?