This posture requires immense abdominal and leg strength in order to support the body for balance. Abducting the arms away from the body strengthens the muscles of the arms, chest, obliques, and lattisimus dorsi located on the middle back. The gluteus medius contracts and adducts the lifted leg while stabilizing the supporting leg. The focus and balance required for the fullest expression of this posture is what makes this an overall body changing posture.
Plank (Uttihita Chaturanga Dandasana)
The arms, chest, shoulders, abdominals, quadriceps, gluteals, calves, and feet are working to assist in holding the body upright. Maintaining this high plank posture with hips level calls on the abdominal muscles for support. Plank pose tones from head to toe.
Side Plank (Vasisthasana)
Supporting the weight of the body on one arm doubles the amount of bodyweight and exerts more effort and energy by increasing calorie burn. The arms, oblique muscles, serratus anterior, quadriceps, and ankles work on overdrive, especially the supporting side of the body.