While lying on your back with your feet flat on the floor shoulder width apart and your knees bent allow for a lordotic/curve in your lower back. Now brace your core to ensure no spinal movement takes place during any of the bridge. While maintaining your core brace raise your hips off the ground as you push your knees to the sides about 2-4 inches (this ensures your glutes are doing the work). If you feel as though a hamstring is going to cramp or is cramping go back to the start position and press your knees further out to the side to increase your glute activation. Once there is a straight line from your abs to your quads (thighs) stop and hold this position for 3 seconds. Now without letting go of your core brace lower yourself to the ground. Be sure to not go up too high as you will be potentially hyper extending your spine which may cause some irritation and pain. Your goal should be 12-15 reps for 3 sets with a 3 second hold at the top. Once you can do this you are ready to progress to the Bridge with Leg Extension.