Step 2: Begin the first movement by shifting your weight slightly forward so your shoulders are in front of your hands; at the same time, lifting your hips up to stack over your shoulders.
Step 3: Through this movement, you are hinging at the hips, pulling from the abs/core, while keeping your legs straight. The final position is the Pike or an inverted V.
Step 4: Return back to the starting plank position in a controlled manner.
Step 5: Repeat this movement several times.
How to progress the exercise
This exercise can be made more challenging by using one leg instead of two., Hold he non-thrusting leg outstretched and parallel to the thrusting leg. Also, Holding your arms crossed over your chest, as opposed to out by your sides, creates a greater stability challenge for your core.
To avoid arching your back during this exercise, focus on squeezing your glutes, as well as pulling in your abdominals, at the same time. The glutes and the abs contracting at the same time will keep your pelvis posteriorly rotated, which will keep your back flat throughout the movement.