Kourtney Kardashian went without makeup as she took a selfie at the gym on Tuesday, Jan. 14 Credit: courtesy of Kourtney Kardashian

Kourtney Kardashian is kicking it into high gear at the gym. The Keeping Up With the Kardashians star went makeup-free in a new selfie she took during a quick workout break on Tuesday, Jan. 14.

"Day one," Kardashian, 34, wrote simply. Alongside the mirror snapshot, the mother of son Mason, 4, and daughter Penelope, 6 months, posed with her right leg up and her dark locks swept to one side. She gave a determined face for the camera as she wore tight-fitting workout pants, a white sports jersey t-shirt and neon green sneakers. During the same workout session she also posted a keek video of herself on a step machine. "Back at it!" she quipped.

Of course Scott Disick's leading lady isn't the only Kardashian to take a selfie while breaking a sweat. This month alone, Kourt's most famous sister Kim has posted two booty selfies at the gym, with younger sister Kendall Jenner photobombing in the second. 

"Barging in on Kim's booty self," the 18-year-old model wrote on Jan. 10. In the snapshot, Jenner stood behind the 33-year-old as they both wore workout pants and sports bras.