For the Grasshoppers, start in a standard push up position with your hands and feet on the ground. From here, twist and elevate your hips while bringing one of your knees to the opposite elbow. Now twist and elevate your hips in the opposite direction until the knee and elbow of the opposite limbs touch. Repeat this motion with as little butt lift as possible for the allotted time and then rest.
This exercise mainly focuses on your core. Bring your knees in activates your abs while twisting causes the oblique muscles to fire. Your shoulders must also being working in order to stabilize your body throughout the exercise.