Flexor Digitorum Profundus (FDP) is a muscle that extends from our elbows, down our forearms, and attaches to the bones of our fingers via its tendons. The FDP muscle is involved in finger flexion (bending/curling our fingers) making it an extremely important muscle for climbing. Our FDP muscles are involved with a variety of climbing grips (crimps, pinches, slopers, jugs, etc.), and developing FDP strength is essential for climbing performance, but it is also one of the most common sources of hand, finger, or forearm pain and injury in climbers.