To cope with the end of a crazy, exciting, exhausting rookie campaign, Bryce Harper did two of his favorite things: spend time with those closest to him at home in Las Vegas, and lift weights. He took a month off after the Washington Nationals’ season ended abruptly in October, and then began the offseason routine that altered his already athletic, growing and built body.

The reigning National League rookie of the year reported to spring training nearly 20 pounds heavier than his playing weight at the end of last season, a chiseled, linebacker-sized 6 feet 3, 230 pounds, ready for the physical and mental rigors of his second season in the major leagues.

“I take a lot of pride in my workouts,” he said, sitting in the clubhouse at Space Coast Stadium this week. “I work as hard as I can to get ready for the season.”

The Nationals’ grandiose hopes for this season rest, in part, on the broad shoulders and unspeakably high expectations for 20-year-old Harper. As a rookie, he injected life and power into the Nationals’ lineup and, despite some growing pains, helped propel them to their first NL East title. He recorded one of the greatest teenage seasons in baseball history, smashing 22 home runs, posting a .817 on-base plus slugging percentage, scoring 98 runs and evolving into an strong defensive player.

The goal this year, though, is higher. “The World Series is the biggest thing on my mind,” he said.

As for his personal ambitions, Harper has been mum since arriving in Viera for spring training. If he were to share them, he insists, people would think he is crazy.

“More extra-base hits,” Manager Davey Johnson said, jokingly, earlier this week. “Probably with more stolen bases, more runners thrown out. You name it, there’s probably a litany of lists. . . . It’s probably .390 with 50 [home runs]. But whatever I get, I’m going to be happy with.”

Tim Soder, who has trained Harper for the past two offseasons, has heard Harper talk about his personal goals for 2013.

“I don’t think he knows how to spell second,” Soder said. “He wants to be number one.”

Harper built his body as big and strong as he could during the winter, an offseason activity he has made a mission since high school. He loses weight quickly; playing baseball nearly everyday for the next eight months, especially the hell-bent way Harper does, can do that to a body. By the end of spring training, Harper figures he will lose 10 pounds.

Since mid-November, when he started lifting again, Harper set his alarm for 4:50 a.m. four times a week, was up by 5 and was at Soder’s training facility in Las Vegas by 5:30 to join a group of minor league and major league players. The intense, non-stop workouts last between 90 minutes and two hours, a little longer on leg days. His older brother, Bryan, 23, a Nationals minor league pitcher, accompanied him.

“It gives me a good time to relax and hang out and clear my mind,” Harper said. “Lifting and stuff really helps me clear my mind. I love it.”

After winning the NL East in 2012, the Washington Nationals are coming into the year with a cacophony of hype. But Thomas Boswell says focusing on this year’s potential is missing the point. (Brad Horn/The Washington Post)

The Nationals wanted to move Harper out of center field as soon as possible, to prevent the mental and physical wear and tear on his muscular body. That was part of the reason for the late-November trade for Denard Span, the type of leadoff hitter and center fielder the Nationals have long coveted. But to Harper it didn’t matter where he was going to play, he was going to show up to camp at 230 pounds even if he was the everyday center fielder.

“I was like 220 last year [for spring training],” Harper said. “So I may be like 250 next year. I’m still growing. I’m still going through those spurts where you’re getting stronger.”

Harper has always lost weight during the season. He lifts only twice a week during the year, just as maintenance, and does bodyweight exercises. After games end and he has showered and talked to reporters, it’s often past 10 p.m. or close to 11, too late for a normal-sized dinner. Harper would often just drive home across the Potomac River to his apartment in Pentagon City and instantly fall asleep.

What sustains him is breakfast — his favorite meal of the day — and a peanut butter and jelly sandwich just before games start. When he is home, however, he gets three hearty meals a day, if not more. He eats whatever his mother, Sheri, makes and places before him. One night the menu is fettuccini, another it’s enchiladas or shepherd’s pie. “She makes everything good and everything is fresh,” he said.

“I just eat as much as I can,” Harper added. “I don’t really care. I don’t really have a diet. I’m still going to eat Fruity Pebbles and Captain Crunch and all these cereals at 12 o’clock at night. I don’t really care.”

Harper mostly hung out at home over the winter. His room at his parents’ house is intact. He played with his dog Swag, who lives there. He spent time with his sister Brittany, her husband and their 5-month-old son, who live in Wyoming. He went to University of Nevada-Las Vegas basketball games. He tried golfing for the first time (”I loved it, but I’m terrible,” he said.) He took trips to Los Angeles, including an appearance on “Jimmy Kimmel Live.” The Harper family went on cruise around Hawaii in late December and, of course, Harper lifted with his father, Ron, on the ship.

“[My parents] love having me around,” he said. “They don’t have me around for nine months. So I’m an absolute homebody. Our family is really close.”

Throughout his entire career, Harper’s baseball ability has had him playing against older players. And in the Nationals’ clubhouse, he is around players on average six to seven years older. Kids his age are in college, not playing in the major leagues. But when he visited his girlfriend Kayla Varner, a soccer player at Brigham Young University, over the winter and watched her games, Harper didn’t regret missing out on college. He is living his dream of playing major league baseball.

“I don’t need to go to college or do any of those parties or anything like that,” he said. “I like playing the game of baseball. I like being around my family and friends. And I’m Bryce when I’m around them. And I’m Bryce in here [the clubhouse]. This is what I love to do.”

Harper admits his rookie season was both exciting and stressful, the mental and physical toll evident. He endured the longest, most arduous slump of his career during the summer. He didn’t rest during the all-star break. Fans chased him for his autograph and photos inside and outside Nationals Park. Reporters vied for his time in the clubhouse. But Harper considers it all a blessing.

“I’d rather be the guy that has everybody doing that than not,” he said. “I love playing the game every single day. I love having fans. And I have a great group of guys that helped me get through those hard times and I can talk to them about anything.”

On Sunday, the first day of full-team workouts, Harper joked with teammates during stretching and warmups. He drilled balls over the left field fence with ease during batting practice, almost in midseason form.

“Anything he sets his mind to he will achieve,” his brother Bryan said in an e-mail. “He told me last year in the middle August, he was going to make a push and get that Rookie of The Year Award, and look what he did in September. I truly believe he can do anything he wants to do in his career . . . Anything he puts his mind to he can achieve. If he wants to win the MVP, he will.”