Kim Kardashian West is Khloe Kardashian's "body motivation".

She shared some bikini pictures of Kim, 35, and wrote: "My body motivation. Mrs. West."

Meanwhile, Khloe revealed she sometimes works out twice a day in order to "shock and challenge" her body.

She wrote on her website: "I definitely don't always do two-a-day workouts, but the reason that I tried them a couple of months back was because I really just wanted to shock and challenge my body.

"First thing in the morning, I would do an intense cardio workout, like running hills. It would really wake me up for the day."

"At around 5 or 6 pm at night, I would head to the gym to work on building muscles. It wasn't only weightlifting, but really any workout to build muscle mass."

However, she doesn't recommend it as a permanent measure.

She said: "Two-a-day workouts should only be for a very short amount of time. Athletes only do it for two to three weeks before they start their season. It's definitely not a lifestyle, and it's way too much on your body to do this for even three months.

"I timed the workouts to be right before my birthday because I was going on a vacation and I wanted to feel good – which I did!

"The downside of working out two times a day is that you have to schedule out your showers and makeup!"