Country superstar Carrie Underwood has vowed to "start appreciating" her changing body after struggling to bounce back following the birth of her second child.

The Before He Cheats hitmaker welcomed her son Jacob, a little brother for her four-year-old boy Isaiah, in January (19), and the singer has since returned to the gym to try and get her body back in shape ahead of her next world tour, which kicks off this spring.

However, in a candid Instagram post on Tuesday (19Mar19), Carrie admits it's been a tough few weeks as she comes to terms with how much her figure has changed as a mother-of-two.

"I'm going to be honest, 'bouncing back' after having Jacob has been much more difficult than after I had Isaiah and I've been pretty hard on myself lately," she began.

"I go into the gym and I can't run as fast or as far. I can't lift as much weight or do as many reps as I could a year ago. I just want to feel like myself again...for my body to feel the way that I know it can."

Carrie, who is breastfeeding her newborn, continued, "As I was working out today, I realized that for the past 11(ish) months, my body has not belonged to me. It was a perfect home for Jacob. And even now it belongs to him every time he drinks his milk."

The singer, who is married to retired ice hockey star Mike Fisher, has now decided to adopt a more positive approach to regaining her fitness, because she recognises how hard her body has worked to give birth to two healthy children.

"As I prepare for red carpets and for life on tour, right now I make a promise to myself to start appreciating what my body CAN do and stop focusing on what it can't," Carrie shared.

"I promise to stop analyzing every angle and every curve and every pound and every meal. I'm going to keep staying the path because it is a journey and as long as I'm always working towards my goals, one day I'll reach them. I'm going to take it day by day, smile at the girl in the mirror, and work out because I love this body and all it has done and will continue to do!"

The star will hit the road for the Cry Pretty Tour 360 in May (19).