I asked Raider Nation which of the physical drills they valued most in a running backs. The top vote getter was the 40 yard dash. Second among the options was the 3 cone drill. Here are the results of the top performers in those drills in the 2012 combine.
40 yard dash
1. Lamarr Miller, Miami- 4.40
2. Ronnie Hillman, San Diego State- 4.45
2. LaMichael James, Oregon- 4.45
2. Chris Rainey, Florida- 4.45
5. Cyrus Gray, Texas A&M- 4.47
5. Isaiah Pead, Cincinnati- 4.47
3 cone drill
1. Chris Rainey, Florida- 6.50
2. Doug Martin, Boise State- 6.79
3. LaMichael James, Oregon- 6.88
4. Isaiah Pead, Cincinnati- 6.95
5. Brandon Bolden, Ole Miss- 6.95
Observations: These are two great drills to combine with each other. The 40 yard dash is pure speed and the 3 cone drill shows agility. The backs who perform well in both areas show they have quickness to elude tacklers at the line of scrimmage and the speed to take it the distance. So it says a lot about Chris Rainey and LaMichael James that they were in the top three of both categories.