The half-kneeling rotation improves core strength and stability with an emphasis on the obliques. The exercise also increases rotational power.
Get in a kneeling position with your legs staggered and your front knee bent at 90 degrees and your back knee on the floor. Keeping your chest tall, bring your arms up so that your hands are just outside your head.
Rotate your torso toward the outside of your front leg. Pause, then return to the starting position.
Squeeze your glutes to help maintain stability.
Do not rotate through your lower back. The twisting occur in your abs.