The first time I looked at this the missing portion of the arms bothered me. After looking for a while it dawned on me that their presence would have made turned this image into an average composition. The cropped arms forces the viewer to explore the image and in the end, marvel at your incredible timing taking this shot. Worthy of a ribbon. Good luck.
Back to comment - Great shot. Fantastic colors and the crop works wonderfully. This is my top pick for this challenge. I hope it does well for you. Bumping up.
IMO, a larger crop to put the runner at the left of the frame and more of the track to the right. Then his right arm would have been in the shot. Also, the loss of his left elbow takes away from the action.
Some will probably say you should've put him on the left side, but I think action shots work well with the person moving out of frame. To me, it emphasizes his speed.
Your focus is terrific, and the color composition is very nice.