I’ve often said that if I were stuck on a desert island and I could only bring one exercise, the humble clamshell would be a strong contender. This exercise is gold for targeting one of the most important and under-utilized muscle groups in our lower body: the deep butt. The deep butt are six little muscles that run horizontally under the gluteus maximus, connecting the head of the femur to the pelvis at various points and angles. These muscles (the obdurator internus and externus, the gemellus superior and inferior, the quadratus