Your hands and wrists consist of a complex system of muscles, ligaments and joints that work together, enabling you to perform a variety of actions with your hands and fingers. Though the muscles in your hands and wrists are some of the smallest in your body, they can be trained and strengthened like any other muscle. Strong wrist and hand muscles can help ward off common hand and wrist problems from strain and overuse, such as arthritis
Hand Muscles
Each hand consists of four sets of intrinsic hand muscles: interossei, hypothenar, lumbrical and thena. These sets do not include the extrinsic muscles that control the thumb. The interossei set is made up of two subsets of muscles, called the palmar and dorsal. The three palmar interosseous muscles and four dorsal interosseous muscles are located between the bones in the hand that connect the wrist with the fingers.
Four hypothenar muscles control the outside of the hand, below the small finger. The four lumbrical muscles, one at each finger, are attachment muscles that connect tendons of the fingers with tendons of the wrist. Finally, the thenar muscles partially control the thumb and consist of abductor, adductor, flexor and opponens pollicis muscles, as well as the first dorsal interosseous between the thumb and index finger.
Extrinsic Thumb Muscles
The thumb has a set of four extrinsic muscles that stretch from the hand, through the wrist and into the forearm. The muscles are the abductor pollicis longus, the extensor pollicis brevis, the extensor pollicis longus and the flexor pollicis longus. The abductor muscle enables you to extend your thumb outward, while the extensor brevis muscle extends the thumb's joint, such as when making a thumb's up sign. The extensor longus also contributes to the extension of joint movement and the flexor muscle enables you to flex your thumb at its two joints.
Wrist Muscles
The wrist contains six muscles: extensor carpi radialis brevis, extensor carpi radialis longus, extensor carpi ulnaris, flexor carpi radialis, flexor carpi ulnaris and abductor pollicis longus. Both the extensor brevis and extensor longus muscles are located on the bottom of the wrist and stretch along the inside of your forearm to the elbow. The extensor ulnaris muscle is located on the outside top of the wrist and extends along the top of your forearm to the elbow. The flexor radialis muscle runs along the bottom of your forearm to the elbow and connects near the base of the thumb. The flexor ulnaris muscle originates at the base of the hand, below your small finger, and stretches along the outside bottom of your forearm to the elbow. Lastly, the abductor longus muscle forms on the bottom of the hand's base, curls around the wrist to the top of your forearm and stretches to the elbow.
Strength Training
You can strengthen your hand and wrist muscles through a number of free weight exercises. These muscles are often automatically involved in a range of upper body exercises, since many exercises require you to grab dumbbells or a barbell. Some exercises, however, are specifically designed to build grip strength and improve the wrists' stability. Good examples of such exercises are barbell wrist curls and Olympic plate hand squeezes, by which you hold the rim of an Olympic plate at your fingertips and slowly curl yoUr fingers inward until you make a fist.
