The quintet - Liam Payne, Harry Styles, Niall Horan, Louis Tomlinson and Zayn Malik - are taking early morning Latin dance fitness sessions as part of their bid to be in top shape ahead of their world tour, which begins in London later this month.
A source told The Sun newspaper: "The lads are not natural movers so them dancing to Latin music is a sight to behold.
"But they know it's good for fitness, so they're putting in the work."
The 'Little Things' hitmakers are also taking part in touch spinning classes, and have been ordered by their management to curb their partying and late nights ahead of the concerts.
It was revealed late last year that the group were told to get in shape ahead of the tour.
A source said in November: "We're concerned about them - and Liam is still healing after he broke his toe when his MacBook fell on it this summer in the US.
"Zayn and Niall have both been on crutches so now they're all on hardcore fitness regimes."
Niall has dislocated his knee a total of 14 times, while Harry was this year forced to take up Pilates to deal with bad posture brought on from his school paper-round.