NEW YORK -- Sandy Alderson revealed details Tuesday of a four-week fitness camp seven players from the Mets organization are attending this month near Ann Arbor, Mich.

Alderson said the participants were Lucas Duda, Ruben Tejada, Wilmer Flores, 2013 first-round pick Dominic Smith and three other farmhands.

The GM added that there was nothing punitive about the assignment, and it was voluntary.

The program is tailored to each participant, so some players' sessions focused more on physical training, while others' centered on nutrition.

"We saw this as a great opportunity to get certain people in a concentrated program, with oversight from somebody who works directly for us," Alderson said. "Each of the players is there for a different reason. There's nothing punitive about it. It's really an opportunity. And we've heard back from a number of them that they're having a terrific time. In fact, Jeff [Wilpon] was there one weekend and hosted them at a football game. To a man, they're excited about what's going on.

"We actually expect that some of the players, and maybe some others in addition, will go back in January."