Grete Eliassen utilizes this complex set of three exercises in order to strengthen her posterior chain. The combination of these exercises really challenges the glutes, hamstrings, lower back and even the core. The goal of the exercise is to "light the hamstrings on fire." Grete does five reps of straight leg hip lifts, five reps of bent knee hip lifts and finally five reps of bridging leg curls. The entire course of the excercise focuses on hip extension and knee flexion. Your hamstrings and glutes help stabilize your body when skiing downhill, as your body is in a flexed position, leaning forward from the hips, while your back and core are working really hard to hold your body in that flexed position, making the Swiss Ball Tri-fecta a great exercise to keep you going strong midseason.