In reply to Fraser:
When I was shooting motorsport, I carried:
1d iv
5d II
400 f2.8 on a monopod and with a 1.4x extender for extra reach
70-200 2.8
24-70 2.8
50 1.4
17-35 2.8
Spare batteries for both, plus cards and sometimes a laptop as well for on the go editing.
All in all, it weighed a lot and it all made for long days!
Post edited at 18:15