A standing kettlebell windmill is a great core exercise that will also help improve your mobility.

Firstly, choose a weight that is light enough to hold it over your head whilst keeping a tall position. If you use a weight that is too heavy, then you will compensate by using your lower back and compromise your posture. Your weighted arm should be out straight and above your head - as if one side is in a star shape! Place your feet shoulder width apart facing in a 45 degree angle away from the side holding the KB. Throughout the movement, keep your gaze up at the KB to avoid internally rotating your shoulder. Push your hips out towards the weighted side keeping your legs straight and your chest open as you lower your opposite hand towards the inside of your foot. If you are holding the KB in your right hand then you will lower down with your left hand to your left foot.

The movement should be performed slowly and with control, holding a strong core. The focus is on being tall and open, and not how far you can bend down.