Kristin Cavallari Flaunts Tiny Bikini After Workout Secrets

Kristin Cavallari showed off a new skimpy bikini as she sunbathed in Cabo San Lucas in  with her friends on Friday.

The veteran had on a black bandeau top with gold accents and a pair of thong briefs that made the most of her slender figure.

The Hills veteran added a black cap and sunglasses to keep the summer sun out of her eyes as she pulled her blonde hair into a ponytail while holding a bottle of water.

This comes days after the 39-year-old made a bold impression on the Swimsuit Runway show in Miami.

The star wore her Uncommon James jewelry with a snake-print bikini and sarong skirt as she walked the catwalk with confidence.

A source told the Daily Mail that Cavallari put her all into looking her very best for the high-profile show that also featured Molly Sims and .

The designer and podcast host looked incredibly toned. 

'Kristin worked out three hours every single day to make sure her body was in top shape, she really to get there,' a source told the Daily Mail.

The three hours were broken up into two sessions as she 'spent an hour and a half lifting weights in the gym in the morning, then went for an hour and a half power walk later in the day,' added the source. 

Cavallari is 5ft3in tall and weighs around 114lb. 

'She always works out but she went the extra mile to prove that she is still hot as she approaches her 40th birthday next year,' added the friend. 

Turns out the blonde beauty was also 'nervous as hell' to walk almost naked in front of hundreds of people at the Mondrian South Beach.

'She had the shakes, she was sweating because she was scared to walk the runway, it took a lot of confidence to do that and she stepped up to the plate,' said a friend.

Cavallari walked the runway wearing RESA's Serpent print bikini styles paired with jewelry from her own brand, Uncommon James. 

This comes after she said her kids think Laguna Beach is 'boring.'

She shares sons Camden, 13 and Jaxon, 11, and daughter Saylor, 10, with ex-husband Jay Cutler but admitted the children .

She told People in April: 'They've seen little bits and pieces, but they think it's really boring. They have no interest in watching a full episode.'

My kids are older now. I've got a teen and then some preteens, and so yes, I can have real conversations with them about it now.

'At the end of the day, I'm just Mom. And yes, this is something I went through, but they know me as Mom ... they know that that's not me.

'There's a huge separation [between Laguna Beach] to who they see on a daily basis, and so they kind of think it's all silly,' she added.

The original show premiered in 2004 and followed Cavallari and her high school friends as they navigated life and love in Orange County, California.

Season one starred seniors Stephen Colletti, Lauren Conrad, Lo Bosworth, Morgan Olsen, Trey Phillips and Christina Schuller, along with juniors Cavallari and Talan Torriero.

The two-hour reunion special features Conrad, Cavallari, Colletti, Schuller and Phillips, along with Dieter Schmitz, Alex Hooser, Jessica Smith Evans and Morgan Smith, who starred in the later two seasons.