The unusual secrets behind Britney Spears’ incredible new body

RUNNING backwards, intense core workouts and tennis are how Britney Spears got her body back for her Las Vegas residency.

LAS VEGAS, NV - MAY 17: Britney Spears and Iggy Azalea perform at the 2015 Billboard Music Awards on May 17, 2015 in Las Vegas, Nevada. (Photo by Denise Truscello/Getty Images)

RUNNING backwards, intense core workouts and tennis are how Britney Spears got her Vegas body back.

The Pretty Girls singer’s trainer has spoken to the Daily Mail about how Brit got into shape for her residency in Las Vegas.

Fit ... Britney Spears and Iggy Azalea at the 2015 Billboard Music Awards. Picture: Getty Images

“She loves to run, but I would make her go backwards,” celebrity trainer Tony Martinez told the Daily Mail.

“She’s like, ‘I’m gonna go backwards?’ I’d be like, ‘Yeah let’s go on the treadmill and walk backwards’. She’d be like, ‘I could lose my hamstrings and my glutes. What are you doing to me?”’

Healthy glow ... Britney on the red carpet at the Billboards in Las Vegas. Picture: Getty Images

Martinez put Spears, 33, through “intense” workouts for 40 minutes three or four times a week

“She loves all core workouts. She’s a very tenacious women. She wants to get it done and get it done right,” he said.

Toned and trim ... Brit in 2009. Picture: AFP

At the MTV VMAs in 2007. Picture: Getty Images

Martinez — who has also trained Pink and Janet Jackson — said he also helped the Gimme More singer clean up her diet.

“I pretty much just wanted her to balance out her proteins, carbs, and fat.

“Everything pretty balanced in that aspect because she was doing a lot of cardio so I wanted her energy up the whole entire time.”