Los Angeles-based fitness expert Gunnar Peterson, Kim Kardashian’s longtime personal trainer, has revealed the unusual and grueling exercise method the reality star will be using to shed her baby weight.

Gunnar Peterson, who also counts Halle Berry and Sofia Vergara among his clients, said he will be making Kim Kardashian push a 200-pound metal “sled” up and down a 90-foot track.

The workout involves her standing behind the apparatus with both hands on the handlebars and driving it forward to generate speed. This motion apparently helps to strengthen the core and tighten the glutes.

Kim Kardashian, 32, who gave birth to her daughter North West on June 15, will be following in the footsteps of top athletes and body builders who swear by the training technique.

Kim Kardashian, who gave birth to her daughter North West on June 15, will be following in the footsteps of top athletes and body builders who swear by the training technique

However, she will no doubt need a few more weeks to recover from her pregnancy as using the device is known to cause high levels of fatigue.

Indeed, the workout is so punishing Gunnar Peterson says that actress Sofia Vergara curses at him in Spanish while she is pushing the apparatus along.

To encourage his clients to keep going and build up speed he tells them to pretend they are reenacting a robbery or playing cat and mouse.

Sled training will form just one part of Kim Kardashian’s step-by-step postpartum exercise routine.

Other treats Gunnar Peterson has in store are dead lifts, power squats, cardio boxing and bouts on the rowing machine.

This combination will target all parts of her body, from arms and shoulders to bum, thighs and core.

Before Kim Kardashian’s pregnancy, Gunnar Peterson said that he worked out with her three to five days per week at his Beverly Hills gym, depending on her hectic schedule.

“She grinds in the gym year round and makes the right choices outside of the gym so the payoff is increased,” Gunnar Peterson previously told Shape magazine.

Gunnar Peterson, a graduate of Duke University, was inspired to become a personal trainer after being overweight as a child.

On her blog Kim Kardashian calls him an “amazing trainer”.

“We always mix strength moves with cardio intervals and I find that combination is what really works best for me… but everyone is different,” Kim Kardashian adds.