There has been a lot talk about a struggling Oakland hitter lately. We won't say his name, so let's just call him J. Reddick. No wait, that's too revealing. Let's go with Josh R. There. The speculation was that he is struggling because Josh R. is moving his head during his swing. Someone asked me if indeed head movement could be the problem. So let's take a look at what hitter's do with the noggin during the swing.
Here is a swing by Josh Donaldson from the side view. Does his head move?
Yes. A ton. Forward and down. His head stays with his body (my cue to hitters is "head over belt buckle") during the stride, then stops moving as his body stops moving linearly. Donaldson's head movement is just a function of his body's movement. Let's take a look at another hitter.
See how much Griffey Jr. moves his head? He lowers his head as his hips are bending during the stride, but then has to make an adjustment due to the pitch location. Griffey Jr. adjusts the bend in his hips pulling his head back up. This allows him to get his arms through and blast a home run.
There has been a lot of talk lately about hitting the outside pitch. Let's see how a couple hitters do it.
Here Brandon Moss does the opposite of Griffey Jr. On the pitch down and away, he has to gain hip bend, bringing his head down to bring his body to the pitch. He was able to take a low and away pitch into the right field stands.
Similar with Andrew McCutchen on the outside part of the plate. See how much bend he gets so he can reach the outside corner. The result is a strong swing resulting in a homerun to center field instead of a fly ball to right. But he has to move his body, which takes his head with it.
Diving into this further, 42% of the pitches McCutchen swings at are on the outside third and beyond. Yet he only 21% of his contact goes to the opposite field. McCutchen covers the plate as well as anyone in the game - and at 5' 10". Looking at his spray chart, McCutchen has 48 hits to right field on pitches on the outer third of the strike zone out of 207. He isn't just poking balls on the outer third into right field. He is moving his body (and his head) to put a good swing on the ball.
Same thing with Robinson Cano. He gets a lot of hip bend to go get the pitch on the outside corner. Result: home run to right-center. It's all in the hips. And when the hips bend, the head moves.
Like McCutchen, 48% of the pitches Cano swings at are on the outside third and beyond, yet only 27% of his overall contact goes to the opposite field.
Take a look at his hits on strikes on the outer third. Keep the head still, go with the outside pitch?
So what gives? Don't coaches teach hitters to keep their heads still so they can watch the ball all the way to the bat? Yes, coaches do teach that. However, hitters don't actually watch the ball hit the bat. Hitters actually make a calculation of where the ball will go by using only about the first two-thirds of the ball's flight while they are striding (for more on this I encourage you to read The Physics of Baseball or The Sports Gene). Hitters have learned to track the ball, make this calculation, and make adjustments all during the stride! In fact, hitters lose sight of the ball in the last 8 to 15 feet of the pitch. And as we saw, the stride is when the head moves the most. Does moving your head hurt your ability to track the ball? Not really (too an extent). Our brain can still process the information while our head is moving. Think about it. If we didn't have this feature, our heads would have to be locked while driving cars.
In fact, keeping your head still can actually be harmful. Check out this swing by Eric Sogard. See how on the inside pitch he keeps his head nice and locked. But this doesn't allow him to adjust his body position and he gets completely jammed.
Compare that with what Donaldson does on an inside pitch. His upper body moves out of the way so he doesn't get jammed.
Now that I have convinced you that head movement isn't important, let me back up a second and say it can be. If someone is taking swings of a tee or on pitches dead down the middle (no adjustments) and they have head movement after the stride is done, then yeah it could (and probably is) a problem. But saying "keep your head still" isn't the solution. That's like solving a flat tire by airing it up. You aren't fixing the problem. The problem is the nail. And in fact, as in with Sogard, telling someone to "keep your head locked in" may actually produce a restricted swing. We have to look at the movement dysfunction and correct it. I might even wager a guess that not moving your head with the movement of the pitch may actually make it harder to track.
And for our pal Josh R., I see neither excessive head movement nor different movement patterns from before on his swing while he was struggling. Was he really "pulling off the ball?"
So what's the verdict? Worry about what the body is doing in the swing, not so much the head.