Spring training is upon us. Pitchers and catchers have reported and it’s nonstop baseball preparation until Opening Day.

But don’t dare think it’s all fun in the Florida and Arizona sun for baseball players. Spring training is a six-week marathon of grueling physical and mental conditioning -- as these photos can attest.

Players are put through exhausting exercises that only elite professional athletes could possibly endure. Exercises such as lifting a leg into the air.

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And more lifting of a leg into the air.

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The agony doesn’t stop there, though. Sometimes the skipping is so intense it can be difficult to carry on a conversation with your teammates. Sometimes.

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Don’t forget about this. This could be tiring. You don’t know.

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The stretching is just as vigorous. Here we see White Sox pitcher John Danks stretch his elbow nearly to the center of his torso.

John Danks worked on his breaking ball Tuesday and felt strong and optimistic. Rick Scuteri/USA TODAY Sports

And still more stretching. This is just one of the exercises that gives star baseball player CC Sabathia his pro athlete physique.

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The intense physical demands are even more painful for athletes coming off an injury. Sabathia’s teammate, Mariano Rivera, has to try to endure it through knee pain.

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All this activity can be exhausting, even to the point of players falling asleep mid-workout.

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But some players are gluttons for punishment and do still more exercising off the diamond. Take a look at Blue Jays pitcher R.A. Dickey doing squats while also curling a four-ounce cellphone.

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It’s not all physical fitness at spring training, however. Players are put through baseball drills, as well.

Unfortunately, financial concerns are still an issue for the Mets, who have been forced to practice without baseballs.

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The Orioles look to make another postseason trip using some of the same training methods that allowed Tom Emanski’s teams to win back-to-back-to-back AAU national championships.

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And the Yankees are preparing for October by practicing exiting the field.

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Teams also use spring training to take team photos.

This allows third-base coaches, such as Cincinnati's Mark Berry, to put on their best tough-guy faces.

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We can also see the excitement level of new Pittsburgh Pirates players such as Brandon Inge.

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But there are portraits that have a more menacing tone, such as this one in which John Lackey appears to be threatening to pitch for the Red Sox again.

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Most players don’t threaten their fans at spring training and, in fact, player-fan interaction is quite common. Here people clamor to get close to a player who may have once dated Kate Upton.

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Yes, players have much to do before the regular season begins, and they can be very tired after a long day of hard work. Here we see the Los Angeles Angels walking up a fight of stairs after an exhausting workout.

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Or maybe walking up the flight of stairs is their workout. Either way, spring training is exhausting.