“Gym selfie with the MILF,” Khloé wrote alongside the picture, which had the two sisters wearing coordinated black workout gear.
Khloé is back in Los Angeles after going on a whirlwind press tour to promote her new TV show, Kocktails with Khloé.
Khloé, 31, has been open about her recent slim-down, saying that she lost around 40 lbs. since adopting a take-no-prisoners attitude to the gym and her diet.
“I definitely think the physical and the mental go hand in hand,” Kardashian previously told PEOPLE. “I feel so good in the gym that it [affects] the rest of my day. It’s a healthy addiction. It’s like buying your sanity!”
The reality star has even become something of fitness and nutrition expert, penning a best-selling book, Strong Looks Better Naked, and frequently sharing gym selfies on Instagram.
Of course, Kourtney, 36, is no slouch when it comes to the gym (just look at those abs!). When Kourtney brought younger sister Kylie Jenner along for a sweat session in December, the 18-year-old said that her sister “has been working hard.”