Finger flexors (flexor digitorum superficialis and profundus)
Flexor digitorum superficialis, flexor digitorum profundus
Pronunciation: FLEK-sor DIJ-ih-TOR-um
For beginners
These are the muscles that actually close your fingers into a grip — even though they're located up in your forearm, their long tendons reach all the way down to each fingertip.
Show the advanced explanation
Because their tendons cross both the wrist and finger joints, a fully extended (cocked-back) wrist can slightly reduce their grip force compared to a neutral wrist — one reason wrist position matters for maximal grip tasks.
Structure & function
- Location
- Deeper forearm muscles whose long tendons cross the wrist and palm to reach each finger.
- Origin
- Humerus, ulna, and radius (varies by muscle and layer).
- Insertion
- Middle and distal phalanges (finger bones), via long tendons that run through the wrist and palm.
- Main action(s)
- Flex the fingers at the finger joints — the primary muscles responsible for gripping.
- Joint(s) crossed
- Wrist joint and the finger joints
- Movement plane
- sagittal
- Innervation
- Median and ulnar nerves
- In daily movement
- Every act of gripping — holding a bag, turning a key, or closing a fist.
- In exercise
- The primary muscles trained by grip work like farmer's carries and dead hangs; work isometrically during almost any exercise that involves holding a bar or handle.
- Commonly confused with
- Often just called 'the forearm' generically, without distinguishing them from the wrist flexors, which are separate muscles that move the wrist rather than the fingers.
- Common misconceptions
- 'Big forearms mean a strong grip' isn't a reliable rule — grip strength depends on training and tendon/nervous-system factors as much as visible muscle size.
Exercises that use this muscle
As a primary mover
⚠ Safety note
Numbness or tingling into the fingers during or after gripping activity can indicate nerve involvement and should be evaluated.
Sources
“The flexor digitorum muscles flex the fingers and are the primary muscles responsible for grip strength.”
Anatomy and Physiology 2e — OpenStax, Rice University · Ch. 11.5 Muscles of the Pectoral Girdle and Upper Limbs
Peer-reviewed textbook · License: CC BY-NC-SA 4.0 · Last checked 2026-07-19
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