Position yourself on all fours with knees underneath the hips and wrists under the shoulders.
Engage your abs and keep your spine neutral, pulling the shoulder blades towards the hips.
Lengthen the left leg until it is straight out and in line with your hips while simultaneously raising and straightening your right arm until it is parallel to the floor. Keep your head and shoulders aligned at all times.
Gently lower your arm and leg back to the starting position and alternate with the other arm and leg.