There’s a revolution happening in the batting cage. We’ve noticed that batted-ball data is changing slightly and that hitters are saying different things about the intentions of their swings. But on the ground, where these hitters are training to improve, a few new tools have appeared that are helping those hitters to realize their intentions with better results. Those tools make a link between hitting and pitching that may open our eyes to the possibility of better development practices in both places.

They don’t look like the bats to which we’ve become accustomed.

Those are weighted bats from Axe. Weighted balls can improve pitch velocity for pitchers, and there’s evidence these bats can improve bat speed for hitters in much the same way. Maybe it’s no surprise, then, that Driveline Baseball — already a leader in weighted-ball training — has embraced these new tools and offered them to their hitters.

“I was up there for three days and my exit velo went from 103 to 106 and that was just working with the overload and underload bats,” said an awed Lucas Erceg of the Driveline campus in Kent, Washington. That’s the Brewers prospect who just hit the ball nearly out of the stadium this spring.

Of course, that’s just anecdotal. Results may vary, as they say. But there are more rigorous studies that back up Erceg’s enthusiasm for overload and underload bats. Coop DeRenne at the University of Hawaii did a study with 50 hitters which found a significant increase in bat speed using over- and under-weighted bats. Jason Ochart, the hitting instructor at Driveline, also did his own study, with 18 batters over eight weeks. The results were eye-opening.

Over- and Under-Weighted Bats and Exit Velocity Comparison Over/Under EV Control EV % Change Exit Velocity – Tee 3.3 1.29 156% Exit Velocity – Front Toss 4.8 1.02 371% Launch Angle 2.1 -1.48 244% EV = exit velocity, represented here by peak mph

The overload bat, the weighted one, makes sense from a weight-lifting standpoint. It’s designed to work out a hitter’s baseball-specific muscles. It follows the same logic discussed by Andre Agassi in his autobiography Open. In it, Agassi recounts a conversation he had with his trainer, Gil Reyes.

I tell him about running with Pat on Rattlesnake Hill, how I feel I’ve hit a plateau. He asks, “How much do you run every day?

Five miles.

Why?

I don’t know.

Have you ever run five miles in a match?

No.

How often in a match do you run more than five steps in one direction before stopping?

Not very.

I don’t know anything about tennis, but it seems to me that, by the third step, you’d better be thinking about stopping… The trick is to throttle down, then hit, then slam on the brakes, then hustle back… You need to focus on building the muscles necessary for starting and stopping.

Baseball players work hard on adding muscle and will do bench press work, but how often are they pushing a weight with both arms off their chest during the game? The trick to training is to do baseball activities in a way that will make the player better at those activities. An overload bat allows the hitter to strengthen the muscles he requires to swing hard, so an on-and-off regimen with those bats, with rest and recovery built in, is akin to Agassi running more shuttle sprints than long jogs.

But there’s another aspect to the weighted bat that may not be obvious at first. The weight begets better mechanics. “One of the common themes is that many of our younger players just don’t get into the ground and use their body correctly,” said Cubs minor-league hitting coordinator Andy Haines. “If you put a heavy object in their hands, without even coaching them, they have to use their bigger muscles more efficiently. They can’t fire from the top. They naturally get into the ground because they want to move the weight better, they do it in sequence, and let their big muscles distribute energy to their little muscles.”

That sequence is very important. Power distributes from the big muscles to the small muscles in a sequence that many call the “kinetic chain.” “The energy is distributed from the body’s center of mass,” as Haines puts it. In this way, hitting and pitching are similar, and weighted bats and balls offer the same opportunity. Instead of teaching little movements that break apart the swing, these instruments allow hitters and pitchers to retrain their entire sequencing.

So that’s the logic of the overload bat. What about the underload bat, though? How does that work? It seems weird to swing a light bat, and it doesn’t fit our narrative so far. In Erceg’s opinion, baseball has once again learned from another sport here. “Olympic sprinters will train running down hill because it gives them that quick-twitch muscle, the pistons firing, so they keep their feet moving,” the Brewers prospect said in camp this spring. “That’s the same concept with the underload bats.”

Haines, who says that the Cubs are using the over- and underload bats in their minor-league camp, explained further. “Muscles fibers are like pistons. They fire fast, or they fire slower, in the recruitment phase. So the heavier weight, the muscles are firing slower for strength, but with a light bat, they fire fast for quickness. So you get the best of both worlds.”

You’ll hear a professional talk about swinging a fungo in the on-deck circle instead of a weighted bat. That might be to get that “quick” feeling, but it also brings up another important point. There’s evidence that swinging the bat with the donut on it right before an at-bat can actually be detrimental to bat speed. Isn’t there the same risk with weighted bats and in-season work?

“Three or four swings with the overload bat, three or four swings with the underload bat, see how it feels,” is how Erceg describes his in-season work. Haines agreed: “We don’t do a ton of repetition with it in spring training, because of the volume and the workload of the day. Not a lot of chance for recovery. That’s more of an offseason, as far as strength-training thing. It’s more of a cage work, smaller volume, for the mechanics right now.”

What do these maintenance drills look like beside some dry swings in the cage? There’s an “internal / external drill where you separate your top and bottom halves,” according to Erceg. And then… then there’s this Happy drill, which should look familiar to anyone who knows about Driveline’s pitching methods.

Shuffle swings AKA 'Happy Gilmores' are a part of our daily tee routine. Here's @daniel_comstock demonstrating that with some 'commentary' ? pic.twitter.com/YDhx4JYDfq — Driveline Baseball (@DrivelineBB) March 9, 2017

According to Ochart, the shuffle swings are about “rhythm, sequencing and separation.” The extra momentum will expose flaws, and the hectic nature of the drill emphasizes feel over specific form. Eventually, this drill starts to sound like a combination of the overload and underload bats: “The extra momentum helps the body move faster and can train the central nervous system to unlock bat speed in the athlete, especially with an underload bat,” but it also “proposes a new challenge to the motor system’s ability to transfer energy via a kinetic link.”

In the end, it’s very much like the “pull downs” we saw with pitching — an effort to bring athleticism and feel back to the mechanical conversation.

We saw some of that with Yonder Alonso’s turnaround. Instead of focusing on details, Alonso changed his mental approach at the plate. He set different targets.

John Mallee, the major-league hitting coach for the Cubs, does the same thing. “We set up the batting cage with markings that show you where the different launch angles are at so you can tell if your hit was good,” Mallee said before a recent spring game. “You have something to aim for.” If you set up a target four feet from the net, 3.5 feet off the ground, and your tee is around 2.7 feet off the ground, you’ve set up a target for 12 degrees — the line drive angle.

Ah, angle. Most of our tools so far have been focused on bat speed, which makes sense because five-sixths of exit velocity comes from the hitter’s own bat speed. But hitting with the right angle is also important. Axe bat, which makes the overload/underload bats you see above, also makes bats that purport to change a hitter’s launch angle via different handles like the two below.

That nonstandard handle was originally designed to help hitters — who often hold the knob of the bat in their palm — avoid the hamate injuries that can come from the traditional bat. A happy discovery recently was that the handle can help the batter alter his launch angle and improve bat speed.

“The comfort benefits were also very clear early on and no doubt opened the doors for conversations and appealed to players recovering from hand or wrist injuries,” said Matt Peterson from Axe bat. “What’s different now compared to just a year or two ago is that we have a rapidly growing contingent of MLB players using the bat and providing feedback on it, as well as more opportunity to collect and analyze data at all levels through sensors, data-capture systems.”

We heard something similar from Mark Trumbo, who said that offseason work in a “flight simulator” helped him feel his way to more fly balls last year. That also echoes something that Mallee said about working with his own son. Working with an Axe bat and a sensor system like Blast Motion and Zepp, Mallee was able to help his son shape the swing he wanted. “I told my son I wanted a positive attack angle, and he was able to look at a number and try to adjust his body to get the right angle.” His son told him that the Axe bat helped him mechanically: “I feel like it doesn’t allow my top hand to turn over and make me cut the ball.”

This author obviously needs a lot of work to get up to speed with Hunter Pence, as his Zepp readout can confirm. “You can learn how to get quicker to the zone” with the Zepp sensor, Pence told me last year, and his bat path confirms he’s found his own way to that outcome using their mapping and data technology. It’s also plain just how much work I’d have to do.

The Axe bat seems to improve launch angle by another means, too — namely, by improving the angle of the hitter’s back. Normally, the bat sorta sticks in a perpendicular manner from the line your back makes. Without the restriction of that knob, though, it’s possible that a batter can change his attack angle without changing the angle of his back. “The handle pre-sets your hand at a natural angle” Haines said of the different Axe handles.

Back to those overload and underload bats: Driveline found that 70% of the users saw increased launch angles using the Axe bats. Add that to the increased exit velocity, and the benefits line up exactly with the changes many major-league hitters are currently trying to make.

A few weighted bats, some targets in the field, maybe a strange bat handle, a sensor or two, and a bunch of hard work, and your bath path may be on its way to optimization. The tools of this revolution will look a little funny. They’ll feel a little funny. But they just might work better.