To begin, start by lying on your side with both knees bent or straight.
Stack your forearm under your shoulder, and push away from the floor, bringing the hips up and away from the ground.
Hold this side plank position with bent knees for 30 seconds, before returning to the floor start position.
To increase intensity, try performing a side plank with bent knees, holding, and eventually progressing to straight legs, with the knees slightly bent.
For an added challenge, you may start by performing plank rotations. From a front plank position, rotate the body to one side, shifting the hips and feet to one side, while you extend the opposite arm.