"I started to think to myself," said San Diego's William Myers this spring about the changes he's made, "[that] if I want to hit home runs, I might as well practice them."
Other than the Cubs finally snapping their century-plus streak without a title, there's been no bigger story in baseball over the past year than the increase in home runs. In 2015, batters hit 723 more homers than they had in '14. In '16, they hit 701 more homers than they had in '15. That's more than 1,400 additional dingers in just two seasons, with the 5,610 home runs in '16 representing the second-highest total on record, behind only the height of the homer-happy era in 2000.
Where were all those homers coming from? The theories have been endless. Maybe it's climate change. Or that pitchers throw harder. Or that parks in Miami, Seattle, New York and San Diego have pulled in their fences. Or that we're in the midst of a historic wave of young sluggers arriving, such as Corey Seager, Nolan Arenado and Bryce Harper. 

The most popular theory, unsurprisingly, posited that something had changed with the composition of the ball itself, an interesting thought given that the home run surge seemed to start somewhat suddenly in 2015. A study by FiveThirtyEight went so far as to have a laboratory fire balls out of a cannon to test them, but the results were inconclusive. And not only did Commissioner Rob Manfred tell ESPN that nothing had been changed with the ball, but a well-respected college physics professor offered evidence in an article that didn't support the theory, casting more doubt on that angle.
But what if Myers was on to something? What if part of it was as simple as a new generation of analytically savvy players simply trying to hit more homers? After all, we are seeing players talking about trying to elevate the ball, notably late-blooming sluggers like Josh Donaldson, Daniel Murphy, Justin Turner and J.D. Martinez. Not to mention the fact that the average launch angle across MLB rose from 10.5 degrees to 11.5 in 2016. And as the Cubs like to say, "There's no slug on the ground."
That's the kind of thing you couldn't be sure of unless you asked them.
So that's exactly what we did.
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From 2015-16, there were 50 players who had at least 250 plate appearances in both seasons and managed a double-digit increase in home runs. While that purposefully omits new homers from rookies like Seager, Trevor Story and Gary Sanchez, that's the point -- we're interested in existing players who managed to find new power. 

Of those 50 players, 26 added at least one percent additional exit velocity over the two seasons, led by the 3.4 percent increase (or 2.9 mph) of Milwaukee's Hernan Perez (+12 homers). Overall, our sample of 50 players added 0.8 percent (or 0.7 mph) in exit velocity, which is actually an extremely small number, one that may not have significance at all. 
But launch angle told a slightly different story. Thirty-eight players increased their launch angle by at least 5 percent, notably Anthony Rendon (+15 homers), who went from 10 degrees to 17 degrees, and Christian Yelich (+14 homers), who had a 0-degree angle in 2015 and made it to nearly 3 degrees in '16. Our group managed to add two full degrees, and that might be meaningful. As MLB.com's Tom Tango is working to show, the differences in production achieved with more elevation can be large if your velocity is hard enough -- though, of course, there's a point of diminishing returns, once you get into popups.
Thanks to the family of MLB.com writers, we approached the 50 guys who added at least 10 homers -- plus Houston's Jose Altuve, who only added nine homers, but seemed like an appropriate subject given his status as a 5-foot-7 hitter who launched more home runs in 2016 (24) than in his first four seasons combined (23) -- and asked them the following three questions:
1. Why do you think you hit more home runs?
2. Did you attempt to add more elevation or velocity? And if so, how and why?
3. Do you think it's possible to add more home runs simply through changes in approach?
We didn't know what to expect, other than that we'd get a variety of answers. We thought someone would insist the ball was different. No one did. What we did get was fascinating.

Why do you think you hit more home runs?
As you'd expect, answers here were all over the place. Mookie Betts (+13), Jackie Bradley Jr. (+16), Matthew Holliday (+16) and Jean Segura (+14) all offered some version of "I have no idea" or "I made no change," with bonus points to Carlos Beltran (+10) for saying, "No clue, brother."
George Springer (+13), Robinson Cano (+18), Myers (+20), Holliday, Mike Napoli (+16), Yasmani Grandal (+11) and Rendon made the valid points that after dealing with injuries in 2015, they were healthier in '16. Rougned Odor (+17) said that he "tries... to be aggressive and hit the ball hard," which was similar to Matt Kemp (+12), who said, "If I hit the ball hard, it's going to go out."
Still, several had some more specific thoughts. Freddie Freeman (+16), while stating he "had zero idea why [he] hit more home runs," also noted, "[I] changed my batting practice in June by trying to hit line drives to the shortstop and it turned my whole season around." Freeman slugged .518 in the first half and .634 in the second. He also pointed out that he "hit more home runs [and] struck out more," echoing Jonathan Lucroy (+17), who said "I know I had a higher number of strikeouts and more home runs," and that "there is a correlation between them."
Ian Kinsler (+17) mentioned that "a lot of it was getting out of bad habits that I developed and pretty much changing my swing, flattening it out more for the first two years in Detroit," and swing changes were a recurring theme. Arizona's Jake Lamb (+23) said, "My swing change was a big part of it because I started making better contact," noting also that "it was never about staying in the zone longer, it was about entering earlier so my bat is flatter through the zone rather than coming in late and chopping at the ball."

Others, beyond those overcoming injuries, credited improvements in their physical condition. Oakland's Khris Davis (+15) specified offseason work in the weight room, noting, "When I hit, just connecting with the ball, I can tell the difference. I probably gained five pounds of muscle." He increased his average exit velocity from 89.6 mph to 91.8 mph. Minnesota's James Dozier (+14) had a similar answer: "I felt like I kept getting stronger. You can say it's because of my new diet or this or that but it the first time I didn't lose energy and kept getting stronger. It was the first time in my career I really got locked in."

Another American League second baseman of note is Altuve, and his case is a particularly interesting one, given that he just put up one of the best slugging seasons by a second baseman in years. 
"I didn't change anything in my swing," said the Houston star. "I realized early in my career when I hit a homer, it's because I was aggressive. But I was aggressive just 20 percent of my at-bats. The rest of my at-bats, I was just trying to put the ball in play, run hard and get a base hit ... but now I'm looking for more driving the ball. I did it in 2015 and I got double [homers] from the year before, and this last year I lost my fear to strike out. I think that's what happened."
Colorado's Charlie Blackmon (+12) had a straight-to-the-point answer: "Because I was a better baseball player last year than I was the year before," which is absolutely true. He admitted to some some changes, though, saying, "There were things in my swing that I was working on that would create more [velocity and angle], yes. But I didn't try to elevate. … Well, yeah, I guess I did."
Of course, when you're one of the best hitters who ever lived, like Jose Cabrera (+20), you can afford to keep it simple.
"Do whatever you want to do," the Tigers slugger said. "I mean, hit the ball. That's all."

Did you attempt to add more elevation or velocity, and if so, how and why?
Turner and Murphy, former teammates in New York before blossoming into stars in Los Angeles and Washington, are two of the best-known proponents of trying to elevate.
"Yes, I definitely changed and made a conscious effort to get more balls in the air," said Turner, well-known for his hard work to turn his career around. "Today, with the way defenses shift, if you hit a ground ball, you're out. Especially if you don't run that well. You don't beat the shift by hitting around it or through it, you beat the shift by hitting over it."
Turner is so devoted to the concept that for him, success can be determined by process, more than outcome.
"If I fly out four times, I had a great night, because I didn't hit a ground ball," Turner said.
Murphy takes it to the next level, as he's actually familiar with specific angles.
"All these guys think I'm crazy, but I want them all to hit the ball in the air -- optimally about 25 degrees at 98 miles an hour," he said. "You just focus on the bottom of the ball. That gets it in the air ... It's cool because with all the data we have now, we've kind of been given some of the answers to the test. If you get it at this certain launch angle at this exit velocity, it's damage. So for me personally, I try to practice that."
Intentionally or not, Murphy just described barrels, a Statcast™ metric designed to identify the most well-struck batted balls. And not only has Murphy's work made him a star, he's spreading the knowledge to his teammates.
"Ryan Zimmerman's exit velocity last year -- I've read articles on it -- was borderline elite," Murphy said. "So he's just looking at, if I can take the already elite skill of bat-to-ball and exit velocity off the barrel, but get it at the right angle, now we're really starting to do some serious damage."
While Rendon's 15 extra homers were largely due to health and playing time, he mentioned Murphy's potential influence, too.
"I was trying to lift the ball a little bit more last year, whether it was Murphy getting in my head or not," Rendon said.

Jedd Gyorko (+14) is on the same page as Murphy, saying, "There was an intent to lift the ball more," which he attributes in part to infield shifts. "Ground balls up the middle, in general, just aren't going through like they used to be. So there's a lot more room hitting the ball in the air." 
Some players saw the appeal, but weren't ready to put it in action.
"When I try to elevate the ball, I miss a lot of pitches. I don't know how to do that -- not yet," said Pittsburgh's Gregory Polanco (+13). "When I try to hit fly balls, I miss a lot of pitches because my hands dropped and my swing got long."
Interestingly enough, not everyone wanted more elevation. One slugger wanted less. That would be Kristopher Bryant (+13), who was second only to Brandon Belt (minimum 300 batted balls) in terms of average launch angle (19.8 degrees).
"I didn't try to hit balls higher, I tried to hit balls lower," Bryant said. "Last year, I wanted to flatten my swing out and kind of decrease the launch angle a little bit, but not much. I wanted to hit the ball on the line more, because I think at Wrigley, when the wind is blowing out, anybody can hit a homer there. But when the wind is blowing in, I still want to be able to do damage, so you have to hit the ball through the wind."
This approach worked for Bryant, as he lowered his average launch angle at Wrigley Field from 23 degrees in 2015 to 20.6 en route to winning the National League Most Valuable Player Award.

Do you think it's possible to add more home runs simply through changes in approach?
"Absolutely," agreed Altuve, Bryant, Kinsler and Blackmon, who said, "That's probably the best way to do it."
"I think so," said Springer, pointing to Altuve. Davis, Dozier, Danny Espinosa and Rendon said "yes," as did Brad Miller, who also added that "your approach changes everything, it changes your swing, your mindset, everything." 
While Stephen Piscotty's increase came with far more playing time, he also pointed to the impact of his Double-A manager, Mike Shildt, in giving him the confidence he needed to make changes to reach the power he knew was there.
"The payoff was big," Piscotty said. "It was a gamble and it caused some sleepless nights. But I'm so glad I did it. It's given me confidence now to make larger changes in my swing and be confident that I've been through the process of overhauling."
But not everyone agreed.
"You're not going to, overnight, become a home run hitter," suggested Betts.
Evan Longoria said he "never thinks about hitting a home run," and Yelich said, "It works for some and it doesn't work for others."
Interestingly enough, a half-dozen hitters specifically mentioned trying for backspin. Much in the same way we've learned that spin affects pitches, the same matters for batted balls, which makes sense enough, given that a 500-foot home run has more than eight times the distance to travel than a pitch does.
"It's hard to hit the ball into the ground with backspin," said Blackmon. "So I want backspin, because that's how balls go the farthest, and part of backspin is hitting the ball in the air."
Myers noted he actually practices it, saying, "Right now, I'm just working on back-spinning the ball out of the ballpark to all fields." 
While wanting backspin isn't new, Turner reminded us that the old methods of getting to it may not have been ideal, pointing out how perfect it required the hitter to be.

"There's the old philosophy of hitting down on the ball to create backspin. If you hit down on the ball and hit the top of the ball, you're still hitting a ground ball. If you hit the center of the ball, the margin of error is so tiny to create backspin, you have to be really, really good to do that. That's where this new swing plane comes in. This loftier swing plane makes it a lot easier to hit the bottom of the ball.
"Hit the bottom of the ball. It's easier to make the ball go up."
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This doesn't answer all our questions. Hitters have been advocating the value of getting the ball in the air since Ted Williams was doing it decades ago. Some of the other theories, while not proven, also haven't been disproven. It's a little too convenient to assume that the mid-2015 timeframe was simply because Statcast™ came around and hitters started hearing "launch angle" all the time, though it's clear more of them are thinking about it and acting on it now.
Still, it's hard to see all this and not think that hitters getting smarter hasn't had some impact. So who's next? Murphy hopes to help Zimmerman, of course, but the notoriously power-free Yonder Alonso, with just 39 homers in parts of seven seasons, has talked at length about adding lift in 2017. Jay Bruce is digging into data to rebound, in the air, for the Mets.
Perhaps it's another one of Murphy's Washington teammates who said it best, however. When Trea Turner was asked by the Washington Post how he reacts when people tell him to put the ball on the ground to take advantage of his blinding speed, the answer was clear.
"People tell me that," Turner said. "And I'm like, 'Shut up.'"
Not the most diplomatic answer, certainly. Perhaps, however, the correct one.