Sailor Brinkley-Cook Shows off Dancer's Physique in New 'DWTS' Rehearsal Photos

Sailor Brinkley-Cook surprised viewers on Monday with her short-notice performance on Dancing With The Stars with pro dance partner Val Chmerkovskiy, and preparing for the next dance is no easy task. The 21-year-old model, who only had three days to prepare for the premiere episode after her mother, Christie Brinkley, broke her arm, shared videos from her rehearsals with Chmerkovskiy on her Instagram Story Wednesday and Thursday. In one clip, she called dancing the "hardest thing" she has ever put her body through.

Brinkley-Cook shared some of the same videos Chmerkovskiy posted Wednesday, notes The Daily Mail. In the background of those clips, Brinkley-Cook was dancing to "Vienna," another song by her mother's ex-husband, Billy Joel. One video shows Brinkley at the rehearsal, wearing a sling.

Brinkley-Cook, whose father is Brinkley's fourth ex-husband, Peter Cook, shared more videos from rehearsal on Thursday. "Dancing is the hardest thing I've ever done with my body," she captioned one clip.

Brinkley-Cook was called in to take her mother's spot with just three days notice, but looked impressive on opening night. The duo danced a foxtrot to Joel's "Uptown Girl," earning an 18/30 from the judges. Fans at home were also surprised by how well she did.

Although she did not look nervous on camera, Brinkley-Cook told Us Weekly after the premiere that she certainly was.

"I didn't want to [do the show] at first, honestly," Brinkley-Cook said. "I was terrified. It was a very scary thing for me.

The whole idea of having to be live on stage, be on TV dancing, that's something I've never done before."
Brinkley-Cook said she was "so scared, but that was the reason I had to do it... I had to surpass the fear. I had to be stronger than the things that scare me."

Brinkley was also encouraging.

"[My mom] told me to have fun with it and to not let fear stop me from doing any of it," Brinkley-Cook told Us Weekly.

Brinkley-Cook later shared an emotional statement on her Instagram page.

"Wow. I have so much to say but for right now i'm just going to say THANK YOU," she wrote. "To my incredible partner [Chmerkovskiy] for being so patient, my mama for being so courageous and inspiring, the whole dancing with the stars cast and crew for their kindness, & everyone who tuned in and showed so much love and support. So incredibly grateful to have had this moment. The journey's just getting started!"

While fans embraced Brinkley-Cook on the show, sources told Radar Online that the other young stars this season - Ally Brooke, 26, and Lauren Alaina, 24 - are not happy.

"Ally and Lauren seem irritated that another young celebrity has come into the mix. They are annoyed there is another young girl to go up against," the source told the site.

Dancing With The Stars airs Mondays at 8 p.m. ET on ABC.

Photo credit: ABC/Eric McCandless