Dr. Saturday does the NFL combine: The 20 and 60-yard shuttle runs

Quickness is both a gift and something that can be trained.

Holy moly, when I felt like I was really moving, I was still slow.

The 20-yard and 60-yard shuttle runs are great tests of acceleration and quickness changing direction. Those are two attributes I can't say I have in great quantities.

On the 20-yard shuttle run, you start the middle of two cones spaced 10 yards apart. Run five yards to one cone, 10 yards back to the other and then five yards back to your starting point. Voila, you're done.

You never get a chance to get anywhere near top speed, unless somehow your top speed is a gear found after your first step. And as soon as you accelerate, you're slowing down to cut back right away.

With the 60-yard shuttle, you run five yards down and back. Then 10 yards. Then 15. (5+10+15)x2 = 60. The 15-yard legs give you a chance to get moving, but you've got to slow down enough to get in and out of your cut as quickly as possible.

All positions do the 20-yard shuttle. The best time at the 2013 NFL combine was by Dallas Cowboys CB B.W. Webb, who ran it in 3.84 seconds. Only one non-running back, defensive back or wide receiver was in the top 30 last year, and that was former Arizona QB Matt Scott, who ran a blistering 3.99.

I wasn't going to come close to any of those top 30 times. My first two runs were very stiff in and out of my cuts -- you can see that clearly on the video -- and the times showed. I clocked in at 5.26 and 5.28 seconds. It may not be evident to the naked eye on film, but in the final drill I focused on slowing into my cut and keeping my weight on my back leg. The result? A 4.95, a time that beat 14 linemen, including three by 0.01 seconds.

The 60-yard shuttle is run by non-linemen, as the drill isn't the most applicable to guys in the trenches. Because of that, I knew that my time was going to be very slow in relative terms.

I just wasn't prepared for how slow it would be. The fastest 60-yard shuttle in 2013 was run by former Missouri WR T.J. Moe, who hit 10.87 seconds. The slowest was former Connecticut LB Sio Moore. He ran a 12.39.

My fastest time was 14.22, which I got on both my second and third attempts. Yes, that means I am almost two seconds slower than a linebacker. And you probably are, too. These guys are quick.

Up next? The three-cone drill, which is also all about quickness and the ability to change direction.

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Nick Bromberg is the assistant editor of Dr. Saturday on Yahoo Sports. Have a tip? Email him at nickbromberg@yahoo.com or follow him on Twitter!