Muscles, explained · Lesson 6
Forearm muscles: how do you build a stronger grip?
For a stronger grip, train the extensors on the back of your forearm too: when you squeeze, they’re the ones holding your wrist. With your wrist bent toward your palm, your grip loses about half its strength, because your flexors are already short. In 13 healthy volunteers, eight weeks of holding the wrist lifted against resistance made their grip stronger.
Which muscles make up the forearm?
Your forearm holds about twenty muscles (Revol et al., 1991), in two groups. On the palm side, the flexors close your fingers and bend your wrist: that’s wrist flexion. On the back, the extensors open your hand and lift your wrist: that’s wrist extension. Their tendons cross your wrist all the way to your phalanges, your finger bones.
Your forearm doesn’t do it all: the small muscles of your palm provide about half of your grip strength (Dell and Sforzo, 2005).
Why does a bent wrist weaken your grip?
Bend your wrist toward your palm, then squeeze hard: you lose about half your grip. In 100 adults, with the wrist held by a splint at 30° of flexion, grip was only half of what it was with the wrist held at 45° of extension: 13.9 kg vs 27.9 kg (Bhardwaj et al., 2011). In 10 others, a flexed wrist cost 40 to 50% of maximal grip (Mogk and Keir, 2003).
The reason: lifted, your wrist keeps your flexors long enough to pull hard; bent, they’re already short, and a short muscle pulls with less force. That’s the length-force relationship of muscle, measured in isolated frog fibers (Gordon et al., 1966).
Why do your extensors work when you squeeze?
When you squeeze, your flexors also pull your wrist toward your palm: gripping or pinching always creates a force that bends the wrist, and the extensors are what balance it so it doesn’t bend (Snijders et al., 1987).
They hold it back, and lift it: with no instructions, 20 adults squeezing as hard as they could set their wrist at about 35° of extension (O’Driscoll et al., 1992).
How do you build grip strength?
Train your extensors too: they hold your wrist. In 13 healthy volunteers, eight weeks of static wrist extension work, at 70% of their strength, five times a week on one side only, made grip stronger on the trained side (Shimose et al., 2011).
Is the hammer curl the best forearm exercise?
The bulge that swells near your elbow during curls is the brachioradialis. It doesn’t close your hand: it bends your elbow. In 21 beginners, 12 weeks of dumbbell curls grew it by 13.5% and 17.6% on MRI, depending on the curl (Kobayashi et al., 2026).
And the hammer curl isn’t its best exercise: in 10 bodybuilders, on the way up, it worked 6% more palm up than with a hammer grip (Coratella et al., 2023). That’s muscle activity, not growth.
Your workout plan, built for your body.
In Tekio, your plan targets your forearms and you watch them progress on your body, week after week.
Sources
Studies checked in PubMed. Measured muscle activity isn’t growth: each fact keeps its study’s population and limits.
- Revol MP, Lantieri L, Loy S, et al. (1991). Vascular anatomy of the forearm muscles: a study of 50 dissections. Plast Reconstr Surg 88(6):1026-33. PubMed · DOI
- Dell PC, Sforzo CR (2005). Ulnar intrinsic anatomy and dysfunction. J Hand Ther 18(2):198-207. PubMed · DOI
- Bhardwaj P, Nayak SS, Kiswar AM, et al. (2011). Effect of static wrist position on grip strength. Indian J Plast Surg 44(1):55-8. PubMed · DOI
- Mogk JP, Keir PJ (2003). The effects of posture on forearm muscle loading during gripping. Ergonomics 46(9):956-75. PubMed · DOI
- Gordon AM, Huxley AF, Julian FJ (1966). The variation in isometric tension with sarcomere length in vertebrate muscle fibres. J Physiol 184(1):170-92. PubMed · DOI
- Snijders CJ, Volkers AC, Mechelse K, et al. (1987). Provocation of epicondylalgia lateralis (tennis elbow) by power grip or pinching. Med Sci Sports Exerc 19(5):518-23. PubMed
- O’Driscoll SW, Horii E, Ness R, et al. (1992). The relationship between wrist position, grasp size, and grip strength. J Hand Surg Am 17(1):169-77. PubMed · DOI
- Shimose R, Matsunaga A, Muro M (2011). Effect of submaximal isometric wrist extension training on grip strength. Eur J Appl Physiol 111(3):557-65. PubMed · DOI
- Kobayashi Y, Maeo S, Eihara Y, et al. (2026). Exercise-specific preferential hypertrophy of individual elbow flexor muscles after incline versus preacher dumbbell curl training. J Sports Sci 1-14. PubMed · DOI
- Coratella G, Tornatore G, Longo S, et al. (2023). Biceps Brachii and Brachioradialis Excitation in Biceps Curl Exercise: Different Handgrips, Different Synergy. Sports (Basel) 11(3):64. PubMed · DOI
These lessons inform; they don’t replace advice from a health professional.