Sprains, fractures, carpal tunnel…wrists seem to get all the attention when it comes to any pain near the hand. And let’s face, it, with the exception of some arthritis or occasional soreness at the base of our thumbs, our hands serve us day in and day out, largely without complaint. Many muscles originating in the forearm contribute to our manual acuity, but the focus of this article is on three groups of muscles specifically within the hand to control movement in our thumbs and fingers.
Thenar Eminence is the regal name for the three muscles that that make that big mound at the base of the thumb on the palm side of the hand. Fortunately for us, the muscle names tell us what they do: the Abductor Pollicis Brevis is a short muscle that abducts the thumb away from the palm and moves it anteriorly, such as when we play the piano or type. The Flexor Pollicis Brevis, as you might guess, flexes toward the thumb toward the fingers and is critical in holding small objects between our thumb and fingertips (as when threading a needle). The Opponens Pollicis opposes the thumb, allowing its pad to touch the finger pads—it’s the clutch and throttle muscle for you motorcyclists.
The pinkie finger has a mirror (or mini-me) set of muscles to the thumb muscles in the Hypothenar Eminence. The Abductor Digiti Minimi abducts the pinkie finger and can be extraordinarily strong when the fingers are spread to grasp a large object like a basketball. The Flexor Digiti Minimi flexes the little finger at the metacarpophelangeal joint (where the finger protrudes from the web of the hand), while the Opponens Digiti Minimi rotates the pinkie toward the thumb, making a deep hollow in the hand when the pinkie and thumb pad touch. Next time you go rock-climbing, thank your pinkie muscles.
While the thumb and pinkie each get three intrinsic hand muscles to themselves, the index, middle and ring fingers share four muscles know collectively as the Central Compartment. The Adductor Pollicis by its name tells us it adducts the thumb, but owing to its span from the base of the middle finger to the base of the thumb in the palm, some categorize it as part of the Central Compartment. Say hello to it the next time you struggle to open a large jar. The Lumbricales may have you stumped. The name reflects neither a body part, nor an action, but a gardener’s best friend—the earthworm—because of the shape. The Lumbricales are long, cylindrical muscles in each finger that simultaneously extend the interphalangeal joints and flex the metacarpophalangeal joints. Cup your hands as if to drink water and you’ll see them. Lastly, the Palmar Interossei and Dorsal Interossei are muscles located along the inside edge of the fingers responsible for closing the fingers and thumb together toward the middle finger (palmar interossei) and spreading the fingers and thumb apart (dorsal interossei) as in when placing your hands on the mat in preparation for downward-facing-dog.
Unless we have fallen on our hands and injured them, these small muscles get paid very little attention. However, they too adhere to the use-it-or-lose-it philosophy and it is important that they stay strong and hydrated from the inside out lest they produce conditions that refer up the chain into our wrists, elbows and shoulders. So, after your next long day of typing, killer game of volleyball or rocking some arm balances, show your hands a little love such as can be found in the YTU 10 Minute Quick Fix for Hands, Wrists and Elbows video clip below (and maybe a manicure too!).
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