I am a beginning DSLR user and am in the process of deciding on what lenses to get for a 400D to use in a similar situation as your gymnast shots. A couple of options are the Canon 85mm f1.8 (which I noticed you used) and the Canon 50mm f1.4.
Could you possibly indicate focal length, aperture and speed for the photos? Tired to check the EXIF but could not see it.
Did you use a flash on any of the photos?
Thanks for your help.
The only one here with the 85mm f1.8 is the 2nd and I think all others are with the 5D with the Canon 70-200mm f2.8. So I'm getting 1/1000s on this 2nd shot but with your 400D you would still only be able to work at 1/250s as you are limited to ISO 1600 (assuming same lighting conditions).
Flash is not allowed at gymnastics competitions so this is where the high ISO and fast lenses are needed.
Seriously the 50mm is not going to be long enough for most of what you want as you are only working at about 15ft.