Kneel on the ground or floor with both hands and knees on the ground.

Slowly lift right arm and left leg up as you exhale while keeping your core engaged.  Inhale and return to the starting position and then exhale as you lift the left arm and right leg.  Continue to alternate while keeping your neck in line with your spine and being careful not to tense up your neck and shoulders as you lift the arm.

You can make this more challenging by kneeing on a Bosu.

This can be very advanced by  kneeling on a stability ball.

Continue for 10-15 reps per side.

2-3 sets