WHAT IS THE FDP?

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.

WHAT IS THE ANATOMY?

The FDP is a muscle that originates from the ulna and interosseous membrane which connects the two forearm bones (radius and ulna). The FDP muscle travels down the forearm and then splits into 4 tendons, each attaching to the distal bone of our fingers, allowing the FDP to play a role in finger flexion.

WHAT ARE THE RISK FACTORS FOR A FDP INJURY?

1. Weak FDP muscle. If our FDP muscles do not have adequate strength to handle the strain and stress placed upon them while climbing, they will be more prone to injury.

2. Weak shoulder muscles. Lack of shoulder strength is a risk factor for FDP injury because if our shoulders are not strong enough to handle the demands of climbing, we will be more reliant on our forearm muscles to compensate for this lack of strength, placing added strain/stress repetitively to the FDP which can produce an injury.

3. Tight/shortened FDP muscle. Shortening or tightness of the FDP muscle commonly occurs due to a combination of strengthening the tissue without stretching or lengthening the tissue. Shortened muscle tissues are more prone to injury because they are less able to handle rapid lengthening of the muscle body and/or tendon and are typically weaker in a lengthened position.

WHAT ARE CAUSES OF FDP INJURY?

1. Tissue overload. Tissue overload occurs when the force we place on the FDP muscle exceeds its tensile strength. This can happen when your foot blows off a hold, suddenly transferring all that load to your fingers, or when you don’t or can’t get all your fingers on a hold, meaning the load can’t be spread across all four fingers.

2. Overuse. The FDP is used for essentially every type of climbing hold/grip, making it an easy muscle to suffer from overuse. FDP overuse occurs when the muscles and tendons are not given enough time to rest and recover between climbing sessions. The stress on our muscles is cumulative over time, ultimately leading to weakening of the tissue and a higher risk of more significant or chronic injury.

3. Forced finger hyperextension. When your fingers are forcefully extended beyond their normal range of motion the FDP tendons are lengthened to an unnatural degree which can contribute to overstretching or tearing of the muscle. In climbing, this could occur as a result of an awkward fall, a foot popping while holding on to a small crimp, or hanging from one arm.

WHAT IS THE PROGNOSIS OF AN FTP INJURY?

As with any injury, the prognosis of an FDP injury will depend on its severity. Chronic or overuse-related injuries may have a correlation to the time the issue has been present. A mild to moderate strain will heal in about 2-3 months while a moderate to severe strain can take up to 4 months, however, each individual’s recovery timeline will vary slightly.

FDP INJURY PREVENTION

1. Listen to your body and take adequate time to rest and recover between climbing days and training sessions. Watch for signs of overuse and keep track of your training and climbing frequency and intensity so that you can see if you’re overdoing it with the volume.

2. Strengthening the muscle and tendons through a full range of motion will make them more mobile and more resilient. Ensure you complement strength training with mobility to avoid shortening of the FDP.

3. Work on strengthening a variety of grip positions. Only training one grip type (i.e. full crimp) will not effectively prepare the tissues for the loads and demands placed on them while climbing. Try working on the open hand or 3-finger drag position while hangboarding to strengthen the FDP and make it more resilient to injury in the future.

4. Repeating the same hard move over and over can definitely cause issues. It is always a good idea to limit your attempts at your hardest problem to a good number to prevent an injury.

EXERCISES FOR FDP INJURY PREVENTION AND REHABILITATION

1. Active range of motion: The full range of motion of the FDP muscle involves moving from full finger and wrist extension to full flexion. To create this motion, make a fist and flex your wrist so that your palm moves towards your forearm, then open up the fingers and extend your wrist so that the back of your hand moves towards the back of your forearm.

2. Tissue mobilization: Perform for 3-5 minutes total of self-massage over the affected area with the amount of pressure depending on the stage of your injury.

3. Stretching: To specifically stretch the FDP muscle, stretch the fingers and wrists into extension but keep the elbow flexed (bent). Since the FDP muscle does not cross the elbow joint, keeping the elbow flexed will prevent stretching other finger and wrist flexors so that the FDP is specifically targeted.

4. Submaximal Holds: Submax holds are relatively long-duration holds performed at low intensity. The purpose of this exercise is to stimulate the tissue without loading excessively and causing further injury. You should be producing a comfortable amount of force that is sustained for 30 seconds and repeatable after a 30-second rest. If you are reaching fatigue by the end of the 30 seconds, you are working at too high an intensity and should reduce the load using a pulley system or band assistance, or by hanging off an easier hold. This exercise should be performed on a variety of holds and grip positions: jugs, slopers, 3-finger drag, and crimp positions.

5. Finger Rolls: Hold an Olympic bar or dumbbell and have the weight rest on a bench or your thigh. Start in a fully flexed position with the fingers and wrist flexed and the elbow slightly flexed as well. Slowly lower the weight until it is just about to fall off of your fingers, then curl it back up. This exercise is great for promoting tendon healing by elongating it while under load.

6. Open Hand Farmer Carries: Perform farmer caries in an open hand position to strengthen the FDP. Ideally, this exercise would be done using a crimp block but can also be done by holding a dumbbell with an open hand position.

If you have suffered an injury to your FDP and want to return to climbing as safely and quickly as possible, pay a visit to the Main Street physiotherapists at Elios Health who have the knowledge, experience, and understanding of the demands of climbing to help guide your recovery and get you back to sending your projects! Your treatment will consist of exercises, manual therapy, modalities such as acupuncture or dry needling, and education to ensure your recovery goes smoothly.

Original Article by Rachel Rubin-Sarganis

Photo by Noah Dustin von Weissenfluh