Taking a dive (into first base)

Legend has it that Eddie Cuthbert of the Philadelphia Keystones was the first player to slide into a base in 1865. The argument about diving into first base likely began that very same evening at the local tavern. The grand majority of baseball people argue that running through first base is far faster than throwing yourself at the ground and skidding into the bag.

The “Run-Through-The-Bag,” or RTTB, crowd is pretty serious about defending its turf. In 2004, the Minnesota Twins coaching staff fined Nick Punto every time he dove into first base. Manager Ron Gardenhire and general manager Terry Ryan eventually had to give in because Punto just couldn’t stop himself from taking the dive.

That pales in comparison to the events of Sept. 28, 2013. The Braves rallied to within a run of tying the Phillies. They had two on with two outs when Chris Johnson hit a ball deep into the hole at short. Jimmy Rollins gloved it and fired to first. Johnson, in a desperate and unsuccessful attempt to beat the throw, dove into the base. Upon returning to the dugout, coach Terry Pendleton physically went after him.

In addition to the “simple physics” that running is faster than sliding, RTTBers cite a higher probability of injuries such as jammed fingers and bruised ribs. They also claim that umps are more likely to call you out because diving interrupts their usual technique of watching for a foot hitting the bag.

The Base Divers (BDers) argue that the physics isn’t that simple. Besides, by diving you prevent injuries associated with landing on a raised bag such as rolled ankles and pulled groins. They claim the confused ump will more often call the runner safe. Furthermore, those calls really demoralize the opposition and fire up your own team.

It is very difficult to settle the arguments about injuries and bad calls, but the simple physics can be examined. There are two notable scientific attempts to answer the question.

In 2007, MythBusters devoted an episode to baseball in which they showed that sliding into a base was faster than not. However, this applies to steals of second or third where the runner must come to a stop. Not surprisingly, they did find that sliding was faster that staying upright and slowing down. This agrees with this author’s findings.

In 2010, ESPN’s Sport Science with John Brenkus focused exclusively on diving toward first versus running through the bag. The result indicated that it is one-hundredth of a second faster to run through the bag. Is that significant?

Well, a 90-mph throw from a shortstop will travel about 16 inches in that time. The distance the very fast runner moving at 20 mph covers in one-hundredth of a second is about 3.5 inches. Both of these distances should be discernable by the ump as he decides on the call. So, it would appear—case closed—the RTTB crowd is correct.

The BDers say, “Not so fast.” The video clearly shows that during the dive, the diving runner gets ahead of the pace set by the player running through the bag. The player running through only regains the lead as the diving runner skids on the ground prior to reaching first. So, if the BDer had made a better decision as to when to dive, he would have won the race. Let’s look at some features of sprinting to get some additional insight into the situation.

image

The force a sprinter feels due to the ground (red) is more or less directed along his leg as shown at the right. The stronger the sprinter, the larger this force will be. The horizontal component of this force (green) propels the runner forward.

To accelerate more rapidly, the sprinter must lean forward. In fact, at the beginning of a race where acceleration is critical, sprinters lean as far forward as possible, thus increasing the horizontal part of the force and, therefore, acceleration. Now we have an explanation for the BDer pulling ahead of the RTTBer. By leaning forward, runners increase the horizontal force pushing them forward.

There is another force on a sprinter working against the motion, air drag. The air drag depends upon several factors, but only two are important here. The air drag grows as the speed increases, and it is proportional to the frontal area of the sprinter. Since air drag grows as a given sprinter accelerates, eventually the air drag becomes equal to the horizontal force exerted by the ground. At this point, the sprinter has reached his maximum speed.

Now, we have another reason that a dive at the finish might be sensible. When a runner lays out, his frontal area drops by a large factor, reducing the air drag that would otherwise be slowing him down. I can hear the skeptical RTTBer now, “So, why don’t sprinters dive toward the finish line?” The answer can be found in the rules which award the race to the runner who’s torso crosses the finish line first. Baseball has no such constraint. A fingertip reaching the bag is as good as a belly button.

So, to summarize the BD point of view: there is video evidence that a diving runner can pull ahead of a non-diving runner. This can be understood by the increased horizontal force and the reduced air drag created by leaning forward. Therefore, a well-timed dive can win the race to the bag.

At this point, the RTTB crowd still could argue that since the timing of the dive is so critical, it is a better bet to run through the base.

Both sides have valid arguments best summarized when Davey Lopes, first base coach for the Dodgers, was asked about diving into first. He said, “It’s fine. Some people are just comfortable doing it. I wouldn’t teach it.”

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Comments

  1. AaronB said...

    Thanks for the thoughts David, I’ve long loved the science of baseball.  Based on this, wouldn’t a “lean towards the tape”, like sprinters do, actually be the fastest technique?  Base runners would still run through the bag,  but would lean at the bag or towards it, giving them a bit of extra force as they push off to the bag.

  2. gdc said...

    When you are leaning far forward it is harder to take a maximum stride.  When you start you need the short steps to accelerate you up to speed.
    The other difference from sprinting is striding over the base doesn’t count, you have to get your strides so your foot (left?) touches the bag.

  3. Anon said...

    let me just point out that on the ESPN video a couple of those dives/slides are not realistic for MLB as he dives hand first into a base that gives way. That might work at lower levels where the bags are designed that way but not in the bigs.

    However, I’m assuming they took some sort of average of a number of attempts so it’s probably a minimal difference but as the video points out, small differences can be big differences.

  4. Lanidrac said...

    Finally, someone who handles this topic competently and in full!  Thank you for pointing out the difference between sliding and diving for first base.  That ESPN sports science segment really bugged me when I saw it.

    The runner indeed has to time it correctly so that his hand reaches the base at about the time he hits the ground (and unfortunately most attempts get the timing wrong, so it may not be worth it), but as you point out it is faster when done correctly.  I hate it when ignorant sportscasters just dismiss the idea completely whenever it doesn’t work.

  5. Greg Simons said...

    Something that bothers me possibly more than runners diving into first is the recent occurrence of players slamming on the brakes just a couple of steps after touching first base.  You know they have to be slowing down before hitting the bag in order to stop that soon, and I’m sure that costs them a base hit now and again.

    There’s no reason to slow down until you’ve run past the bag.

  6. Tony Cunningham said...

    I should think that the timing of the dive would have to be very precise to maximize the advantage.  You’d have to time it so that the reach would outweigh the extra striding.  If you do it too soon or too late, I assume that any possible advantage would be eaten up.  Perhaps Nick Punto and company have the knack of knowing just when to do it (unless a player’s stride is identical each time down the line, which seems unlikely give the vagaries of the swing and getting out of the box after hitting the ball), but I would imagine that unless players practice it a whole lot, they’d often be off on the timing and so they’d often negate theoretical advantages.  After all, theory and practice are likely to diverge here unless a given player really has it down.

  7. Bob B. said...

    Not directly related, but the whole run through the base or slide always makes me think of Jeremy Giambi and that play at the plate in the playoffs some years ago that the A’s lost and Giambi was widely criticized for “stupidly” not sliding.

    Part of the reasoning I presume was trying to avoid the tag but I always thought it was silly he took so much heat for it considering that it was traditionally viewed as the faster way.

  8. Steve K. said...

    Something else to consider, not directly related to the “which gets you to first base faster” issue but more along the lines of which is more likely to allow you to be safe at first is that by diving, you avoid the possibility of a sweep tag by the first baseman on an errant throw.  While errant throws are relatively rare, especially at the major league level, they do seem to happen at least once every few games that I watch.

  9. Dave W said...

    Another important point is whether you step on the front of the bag or the top of the bag.  Obviously it’s quicker if you step on the front of the bag.  At a coaching clinic put on by the Twins I learned a neat trick that I doubted, but when tried found it to be true, and have since passed it on to players.  When you are running down the line, if you focus on the front of the bag your mind will adjust your stride length accordingly and you will hit the bag every time in perfect stride.  No more injuries from runners taking that long, last lunge at first base and twisting an ankle or jamming a knee. Try it out, it works great.

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