Hand strength measurements are of interest to study pathology of the hand that involves loss of muscle strength. Examples of these pathologies are

carpal tunnel syndrome Carpal tunnel syndrome (CTS) is the collection of symptoms and signs associated with median neuropathy at the carpal tunnel. Most CTS is related to idiopathic An idiopathic disease is any disease with an unknown cause or mechanism of apparen ...

nerve injury Nerve injury is an injury to nervous tissue. There is no single classification system that can describe all the many variations of nerve injuries. In 1941, Seddon introduced a classification of nerve injuries based on three main types of nerve f ...

tendon A tendon or sinew is a tough, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability ...

injuries of the hand, and neuromuscular disorders. Hand strength testing is frequently used for clinical decision-making and outcome evaluation in evidence-based medicine. It is used to

diagnose Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine " cause and effect". In systems engin ...

diseases, to evaluate and compare treatments, to document progression of muscle strength, and to provide feedback during the rehabilitation process. In addition, strength testing is often used in areas such as

sports medicine Sports medicine is a branch of medicine that deals with physical fitness and the treatment and prevention of injuries related to sports and exercise. Although most sports teams have employed team physicians for many years, it is only since the ...

and

ergonomics Human factors and ergonomics (commonly referred to as human factors) is the application of psychological and physiological principles to the engineering and design of products, processes, and systems. Four primary goals of human factors learnin ...

. In general, hand strength measurements can be divided into manual muscle testing and dynamometry.

Manual muscle strength testing of the hand muscles

In clinical practice, hand muscles are most often evaluated using manual muscle strength testing using the Medical Research Council (MRC) Scale. In this scale, muscle strength is graded on a scale from 0 to 5. For evaluating the strength of the intrinsic hand muscles, a small modification to the standard MRC grading has been made so that grade 3 indicates ‘full active range of motion’ as compared to ‘movement against gravity’:

Modified Medical Research Council Scale for measuring hand muscles

Grade 5: full active range of motion & Normal muscle resistance Grade 4: full active range of motion & Reduced muscle resistance Grade 3: full active range of motion & No muscle resistance Grade 2: Reduced active range of motion & No muscle resistance Grade 1: No active range of motion & Palpable muscle contraction only Grade 0: No active range of motion & No palpable muscle contraction Manual muscle testing, however, has a number of limitations. One limitation is that the MRC scale is an ordinal scale with disproportional distances between grades. Another limitation of the MRC scale is that the scoring depends on the judgment of the examiner. Finally, with the 6-point ordinal MRC scale, it is difficult to identify relatively small but clinically relevant changes in muscle strength.

Grip and pinch dynamometry

To create more quantitative assessments of hand muscle strength, dynamometers have been developed. These

dynamometer A dynamometer or "dyno" for short, is a device for simultaneously measuring the torque and rotational speed ( RPM) of an engine, motor or other rotating prime mover so that its instantaneous power may be calculated, and usually displayed by ...

measurements are more sensitive to change compared to manual muscle testing and render outcome on a continuous scale. In clinical evaluation and research studies on patients with hand problems, muscle strength measurements are usually based on

grip strength Grip strength is the force applied by the hand to pull on or suspend from objects and is a specific part of hand strength. Optimum-sized objects permit the hand to wrap around a cylindrical shape with a diameter from one to three inches. Stair rai ...

and pinch strength dynamometry. The most commonly used grip and pinch dynamometers are the Jamar dynamometers and similar devices by other manufacturers. In several patients groups, these measurements have a good reliability and validity. In addition, grip- and pinch strength are functionally relevant to measure the combined action of a large number of intrinsic and extrinsic hand muscles as well as the combined action of a number of different joints. By comparing outcome with normative data, the amount of muscle strength loss can be determined.

Rotterdam Intrinsic Hand Myometer (RIHM) palmar abduction measurement

Dynamometry of the intrinsic hand muscles

For more specific dynamometry of the intrinsic muscles, intrinsic hand dynamometers have been developed. The advantage of these dynamometers is that they to do not measure a large number of muscles in combined action, but can measure single actions such as thumb opposition of index finger abduction. One such dynamometer is the Rotterdam Intrinsic Hand Myometer (RIHM). Reliability and validity of this dynamometer is comparable to grip- and pinch dynamometers.

References

External links

Myoton: Publications
{{DEFAULTSORT:Hand Strength Hand