Drew Storen reported last year to Washington Nationals spring training slimmed down, toned and in better shape than he could remember. He spent this winter making sure he wouldn’t make the same mistake.

In baseball, Storen discovered, superlative physical condition can be a miscalculation. He withered to as low as 175 pounds during the summer. His energy waned and he struggled to recover between games. Before this winter, Storen had never weighed more than 185 pounds. He weighs 200 pounds now, thick through the neck and chest, and he thinks he will be better because of it.

“You kind of need to have a little meat to get through the rigors of the season,” Storen said. “I kind of like it. I feel way better.”

Storen had waged the daily battle of a ballplayer, the constant struggle to find, reach and maintain an ideal weight. Though it varies by individual, most players aim to pack on weight in the winter. They know it will melt away through a summer of sweltering pregame workouts and active nights on the field.

Last year, after Adam LaRoche’s attention deficit disorder medication suppressed his appetite, he dropped 10 pounds off his target weight and lost bat speed and power at the plate. Bryce Harper vowed in the fall he would bulk up “as big as a house,” believing extra muscle would sustain him over the marathon season — he entered last spring at 238 pounds and ended the season less than 220.

Doug Fister joined the Washington Nationals this winter after a trade with the Detroit Tigers. A left-handed batter and right-handed thrower, Fister will be an asset to this season’s starting pitcher lineup. (Whitney Leaming/The Washington Post)

“I had an old coach a long time ago,” Nationals head athletic trainer Lee Kuntz said. “He said, ‘Did you ever see a skinny guy finish the Bataan Death March?’ At the time, I was young and I didn’t understand the wisdom of it. But this is a war of attrition. If a guy comes in light, especially in D.C. or if you’re playing a place like Atlanta, you’re going to trend lighter as the season goes. If you come in light, you’re going to be in trouble.”

The Nationals encourage players to weigh in daily during spring training, in part to catch warnings of dehydration. Especially for players coming from warmer climates, spring workouts can cause players to shed weight quickly. In the summer, in scorching cities such as Atlanta, players can lose between five and eight pounds per game, Kuntz said.

Players track their weight with precision. Outfielder Scott Hairston, a 10-year veteran, wants to weigh 197 pounds during the season. He used to come to spring training at about 205 pounds, but his metabolism has slowed with age, and now he arrives weighing 200. He steps on a scale every day during the season; if he loses weight, he eats more protein or lifts more weights. Saturday morning, he weighed 199 pounds. By opening day, he wants to be not 198 or 196, but 197.

“It’s so important,” Hairston said. “I play my best when I’m 197.”

Early in his career, shortstop Ian Desmond bulked up in the winter and entered spring training at 210 pounds. In 2011, he struggled in the first half of the season but, as he shed about 10 pounds throughout the course of the year, he finished strong. He realized he had tended play better in the second half.

“I was like, okay, you’re having really good success at like 210,” Desmond said. “So why are you coming in at 220?”

Desmond now tailors his winter conditioning program to arrive at spring training lean and strong. For the second straight year, he weighs 210 pounds with 7 percent body fat.

“Throughout the course of the year, I can gain weight, so that way I’m not losing energy towards the end of the season,” Desmond said. “I feel like that, for me, has been better. I think my numbers have shown. Who knows if that really matters or not? But I feel good.”

Every two weeks during the season, on the morning of Sunday home games, every player weighs in. It allows the Nationals’ training staff to track how a player’s weight fluctuates during the season and provides a historical record. The number on the scale, over time, creates a data point, a possible indicator of success or failure.

“If you look at a guy’s weight record, you can see how he tends to track,” Kuntz said. “You can also go back and look at their stats. Where was this guy when he was at his best? Did it correspond with any drastic weight gain or weight loss? It kind of helps put another piece of the puzzle together.”

Superstition may drive some players’ desire to hit a specific point on the scale. Just in case, as long the player is within a pound or two of his ideal weight, Kuntz may tell him he weighs that much — and then write down his actual number.

At the end of every year, Nationals strength coach John Philbin meets with every player. He records one final weight and outlines a winter plan. The Nationals’ training staff maintains contact with players’ personal trainers. Philbin calls players once a month early in winter. As spring nears, he either visits players at their homes or calls them twice a month. With each call, he asks for their weight to add to the record.

“We can find out the guys that are sandbagging,” Kuntz said. “ ‘Oh, I’m 210.’ And then come in, and they’re 225. Really, dude?”

While some players fluctuate like the stock market, others remain static. Third baseman Ryan Zimmerman ballooned to 230 pounds after wrist surgery in 2007. But once he could start working out again, he slimmed back down to 220. He has weighed between 217 and 223, he said, for the past five years.

“I don’t really have to do too much,” Zimmerman said. “I make an effort to eat good, get some sleep, things like that. The past five years, that’s just how it’s been.”

Zimmerman is a rarity, a baseball player who manages his weight without obsessing. Most of his teammates keep meticulous watch on their weight, down to the last pound. “I’d rather be 198 than 196,” Hairston said. “You got to know your body.”