Kylie Jenner shared a selfie at the gym and promised to be strong after giving birth to her second child, despite recent knee and back pain.

No pain, no gain! Kylie Jenner has taken steps in her fitness journey within months of welcoming her son.

On Monday, the 24-year-old reality star gave her followers another update on her postpartum transformation and shared clips of her story on Instagram when she was in the gym, even though she was struggling with knee and back pain.

"No vacation!" writes next to a mirror selfie posing in a harmonious brown set of sports bras and spandex.

"Four months after giving birth," Jenner added another shot on the treadmill. "My back and knees hurt a lot right now, so it's slowing down my training, but I'm on a mission to step up again. Star Kardashians and Travis Scott will welcome their second child, one boy, in February. Together they are also the parents of 4-year-old daughter Stormi Webster.

In April, Jenner published a post on her Instagram story, where she first gave fans a glimpse of her weight gain - and subsequent weight loss - after her second pregnancy.

"This pregnancy has gained 60 pounds again," Jenner wrote with a black-and-white image of herself running on a treadmill, noting that she currently "weighs less than 40 pounds."

The mogul, Kylie Cosmetics, added that she was "just trying to be healthy and patient" and said that a combination of walking and pilates are her favorite exercises that help her lose weight for an extra baby. After she was born, she announced on her Instagram Stories the following month that her son would no longer call her by that name.

In an April interview with USA Today, Jenner revealed that she and the rapper "Highest in the Room" "have not yet legally changed their names."