Lie on your back with a neutral spine and your hips and knees at right angles. Press your left elbow into your left knee and, with your elbow straight, rest your right arm against the right knee.
Press your lower back into the floor and draw your belly button into your spine. Lift your shoulders off the ground, while continuing to squeeze your abs and glutes.
Keep your torso and spine stable as you lengthen your right arm and leg out until they are almost parallel to the floor.
Pause briefly before bringing your arm and leg back to the starting position.
Continue this movement for the full 40 seconds.
Once the 40 seconds is up, rest and complete the move on the left side.