Side Planks

Side Planks are a great exercise for strengthening your obliques, hips and low back.
According to spine expert, Dr. Stuart McGill, strength in a side plank is an excellent exercise for spine stabilization.
The top image shows my client Deborah in an intermediate side plank variation.  Notice that her top leg is in front.  This allows her to use her glutes to move into the position and help stabilize her. It is almost like doing a side bridge.  The weight she is holding is optional.  Adding the weight increases the difficulty of the exercise. Start by holding this position for 10 seconds and build to 30 seconds.
The bottom image is advanced.  As a side note, notice how Deborah smiles during this difficult exercise.  Challenging herself makes her happy! 
By lifting the top leg, she creates a less stable position and puts more demand on her hips and pelvis, and of course her obliques and low back. Once you master the top variation and can hold the side plank for 30 seconds, give this a try but don’t add the weight yet, add it later when you can hold the top leg lift for 20-30 seconds.