Step 1: Starting position is on one leg, facing sideways towards the TRX anchor.
Step 2: One leg is outstretched to the side, towards the anchor, inserted in the TRX stirrups. The position of the supporting leg, including both hips, as well as the knee and toes of the supporting leg, is facing forward.
Step 3: Begin the movement by bending the supporting leg as you lunge sideways towards the anchor. The TRX supported leg remains extended (with a ‘soft’ knee). as it glides toward the anchor. Stop when you feel a stretch in the inner thigh ( not in the knee), then squat back up to the starting position.
Step 4: Repeat this movement several times, then switch legs and repeat.
How to progress the exercise
Progressing the side plank from the forearm position to that with the hand on the floor can be the first step. From there, variations can be made such as reaching top arm up towards the ceiling, lifting top leg up to the ceiling. Basically, reducing the contact point of your body with the floor as well as lengthening the lever arm (ie: arm up to the ceiling, top leg stretched up to the ceiling), will definitely increase the challenge for this exercise. Movement of the upper extremities can also be another option to progress this exercise, creating a need for more dynamic stability. Placing your elbow or hand on a BOSU will add a great balance challenge!
Although the regular plank is the most common exercise, the side plank is sometimes overlooked and should be incorporated into your routine as a foundation for many exercises requiring side to side stability.