Hand movements are orchestrated by the actions of a multitude of muscles, nerves, ligaments and joints in the arms, wrists and hands. The complex interplay between these body structures makes both fine and coarse hand movements possible. Hand strength is the force with which a person is capable of gripping an object. It can be quantified by measuring the force with which a person is able to squeeze an object with his or her hands.
A special instrument called a dynamometer can be used to measure this force. Using a dynamometer, the average hand strength of adult men has been estimated to be between 105-112 pounds (or 48 to 51 kg). Similarly, the average hand strength of adult women has been estimated to be between 57 to 65 pounds (or 26-29 kg).
How strong is the hand grip?
Hand strength differs from person to person and is dependent on factors such as muscle mass, body size, physical fitness, age and sex of the individual. The grip strength is higher is more muscular persons who do heavy physical work. Hand strength is also generally correlated with the sex of the individual. Men have greater hand grip strength than women.
The force exerted by the hands while gripping an object mainly depends on the strength of the nerve signals that make the muscles in the hands and the forearms contract. However, factors pertaining to the joints and ligaments in the hands, wrists and forearms also affect hand strength.
Causes of Hand Weakness
Each individual usually has a qualitative idea about his or her hand strength in everyday life. If it becomes weak, the affected individual usually becomes aware of it without the use of any specialized equipment. Further tests will, however, be necessary to determine the extent and the exact cause of weak hands.
There are many causes of weak hand grip. Problems with nerves, muscles, joints and ligaments could cause the hand grip to weaken. Some of these causes are described below.
Nerve problems are the most common cause of weakened hand strength. Some of these conditions are:
- Carpal tunnel syndrome: Carpal tunnel syndrome is one of the most common causes of wrist pain and weak hands in the modern world. It is an occupational hazard of working with computer keyboards for extended periods of time. Carpal tunnel syndrome is caused by a compression of the median nerve in the wrist, resulting from repetitive motions of the wrist while using computer peripherals such as the mouse and the keyboard.
- Brachial plexus injury: Brachial plexus refers to the meshwork of nerves in the neck and the shoulder regions that give rise to nerves that extend into the arms. These nerves give signals to the muscles of the arms and bring about their movements. Injury to the brachial plexus can result from traumatic events such as accidents, nerve compression or nerve diseases. Hand movements become restricted and weak when the nerves of the brachial plexus get injured or diseased.
- Radial neuropathy: Movements of the wrist, hand and fingers is brought about by the stimulation of muscles in these regions by the radial nerve. The radial nerve arises in the brachial plexus. When the radial nerve gets injured or diseased, a condition known as neuropathy, the muscles in the wrist and fingers don’t work properly. This leads to wrist drop or finger drop (also known as Saturday night palsy).
- Ulnar neuropathy: Ulnar nerve also arises in the brachial plexus and innervates muscles in the forearm and part of the hand. Damage or disease to the ulnar nerve results in weak or paralyzed hands. The fourth and the fifth fingers are mainly affected in ulnar neuropathy. An example of ulnar neuropathy is the cubital tunnel syndrome, in which the nerve damage occurs within the elbow region.
- Median nerve palsy: The median nerve arises from the brachial plexus and moves into the hand through the carpel tunnel in the wrist. Injury to the median nerve results in a condition known as the “ape-hand deformity” in which wrist and hand movements become severely restricted.
- Cervical radiculopathy: The nerves in the hands have their origin in the neck region. Any injury to these nerves as they emerge from the spinal cord in the neck can cause symptoms such as weakness of hands, tingling sensations, numbness and even abnormal reflexes.
- Amyotrophic lateral sclerosis (ALS): ALS, also known as Lou Gehrig’s disease and Charcot disease, is a degenerative nerve disease that results in the death of motor neurons that control muscle contractions. Cramps and muscular weakness are major symptoms of this motor neuron disease that affects multiple regions of the body.
Apart from the conditions mentioned above, a host of other diseases can cause nerve damage and hand weakness. Examples include Parkinson’s disease, multiple sclerosis, Guillain-Barre syndrome, multiple sclerosis, polio, diabetes, and stroke. In addition to diseases, toxins can also cause nerve damage.
Movements of the hands are brought about by the nerves signaling to the muscles of the hands. Therefore, injury or disease to the muscles also lead to weakness of the hands. Some examples include:
- Myasthenia gravis: Myasthenia gravis is an autoimmune disorder that results in the destruction of the muscles in various parts of the body. Hands and arms are also affected in this condition.
- Muscular dystrophy: Muscular dystrophy is a genetic disorder that results in progressive weakening and destruction of the muscles in the body. The symptoms of muscular weakness are detected at various stages of life. Some affected individuals show severe symptoms right from their childhood, whereas others don’t develop severe symptoms till they become teenagers or young adults.
- Tendonitis: Tendonitis refers to inflammation of the tendons that connect the muscles to the bones. Hand weakness occurs when inflammation affects the tendons of muscles in the arms and the hands. Tendonitis is usually caused by chronic repetitive motion injury. However, acute injury may also result in tears in the tendon and cause weak hands.
- Polymyositis: Polymyositis is a rare inflammatory disease that affects the muscles on both sides of the body and causes progressive weakening of the muscles in the limbs. The exact cause of this condition is not known.
- Muscular atrophy: Muscular atrophy, or wasting of the muscles, can be caused in a variety of conditions such as AIDS, cancer, and malnutrition.
In addition to the abnormal nerve and muscle conditions mentioned above, weak hands can be caused by factors that affect the proper functioning of the joints and the ligaments in the hands. This can occur in conditions such as rheumatoid arthritis, wrist and hand fractures, blood clots in arteries, and chronic use of corticosteroid drugs.