Machine Seated Pec Deck Flys: Target Area, Preparation, Correct Position and Technique of doing it. If you really care about your fitness, you must visit our website http://www.uft1.com/ to get some great fitness insights. Primary Muscle(s): Pectoralis Major Secondary Muscle(s): Deltoid, Anterior Biceps Brachii, Short head Coracobrachialis Preparation: Adjust the seat so the handles are at shoulder height. Select the desired weight that fits your workout program. Then adjust the handles so when at rest, your chest is slightly stretched. Execution: Grasp the handgrips with your elbows slightly bent. Rotate your shoulders so your elbows point behind you while keeping your elbows from dropping below your shoulders. Place your head and back against the pad and bring handles together in a fluid motion. Then smoothly return to starting position. Repeat Note: For proper breathing, exhale when pushing in inhale on the return.