A friend adjusted the direction of the video camera while I was shooting one of two D300 bodies a couple of years ago. You can hear me clicking away in the background. I had to use two bodies, set up side by side on two tripods because the buffer filled after about 12-14 shots. One usually had a 200-400 and the other had a 70-200 on it. I'd go back and forth to the two bodies as one filled.
I still photograph the running horses, but use a D4 now. The run takes about 1.5 to 2 minutes on average and I fill the buffer even on a D4! That's about 90 14-bit images in RAW. I have a 64 gig Sony XQD series S card in the main slot and a 32 gig Lexar 1000x in the other.
Even though I fill the buffer on the D4, it empties quickly with the S Series XQD cards. I usually come home with about 250-300 photos with the D4 and another 40-60 on a D800 set up beside me with a 70-200 and a remote. At 10 FPS on the D4, I can pick clusters of horses and then do a burst of about 10 shots, then pick another cluster and keep shooting throughout the entire run.