What Can Handgrip Strength Tell the Therapist about Hand Function?

Abstract

Can the measure of grip strength serve as an indicator of an individual's ability to use his or her hands in activities of daily living? This is the topic explored in this brief, yet engaging article from the British Journal of Hand Therapy . The authors investigate the important issues involved in measuring grip strength and examine its usefulness to us as clinicians. Instruments used in the measurement of grip strength and the correct protocols for doing so are discussed. Adapted sphygmomanometers are still used in several departments, but this measures grip pressure, which is not as reliable a measure as force to record grip. The ASHT recommends use of the Jamar dynamometer because of its well-documented reliability and validity. This instrument may be difficult to grasp for individuals with weakness in their hands. The scale may not pick up small changes in strength as well. There are newer, more sensitive tools that measure grip in newtons. This makes it easier to record small changes between trials. The authors suggest frequent recalibration of instruments to ensure their accuracy. The mean value from three grip strength recordings should be used as suggested by the literature. The patient's positioning is standardized with the shoulder adducted, elbow flexed to 90°, the forearm in neutral, the wrist in 0–30° of extension, and 0–15° of ulnar deviation. The authors briefly discuss the issue of submaximal (feigned) effort and conclude that the amount of variation between trials may in itself not be a good and reliable indicator of submaximal effort. We often compare our patients' grip strengths with normative data. But we need to be confident that the norms we use are applicable to our patient population. Hand function has been described as the ability to use the hand to perform daily tasks. Hand function includes range of motion, sensation, coordination, dexterity, fine motor skills, as well as grip. So what does grip strength actually tell the clinician about hand function? The authors review the research concerning grip strength and hand function and divide the studies into three categories according to the research methods used: 1. Studies that compare participants' grip strength with performance on a particular activity of daily living. 2. Studies that compare grip strength with performance on a series of tasks resulting in an overall score. 3. Studies that compare grip strength with participants' subjective evaluations of their ability to complete daily living tasks. Comparing grip strength with performance on an activity of daily living: One study explored the relationship between grip strength and a person's ability to open six different containers. Grip strength for each individual was recorded, and his or her ability to open the containers was noted. In a study of college students, greater grip strength did not correlate with better performance at opening containers. The study was repeated with older participants, and a fair correlation was established between power grip and the ability to open two of six containers. This suggests that reduced grip strength may lead to difficulties with opening everyday containers. Comparing grip strength with performance on a series of tasks resulting in an overall score: Several studies have been conducted on small samples comparing grip strength with overall upper extremity performance. Hand function as measured by the Jebsen Hand Function Test and the Purdue Pegboard Test was compared with Jamar dynamometer grip strength recordings. Moderate to weak correlations have been reported on a variety of patient populations. Due to small sample sizes, the information may not be generalized to other populations. Comparing grip strength with participants' subjective evaluations of their ability to complete daily living tasks: The authors mention several studies that compared grip strength measurements with patients' subjective evaluation of their ability to perform activities of daily living. The subjective evaluations used included the self-report Health Assessment Questionnaire, the Disabilities of the Arm, Shoulder and Hand Outcome Questionnaire (DASH questionnaire), and the Michigan Hand Outcome Questionnaire. The studies varied in their use of grip strength–measuring instruments. All studies had small sample sizes and were patient-diagnosis specific. In general, a range of correlations was found between grip strength and functional outcomes as measured by patient self-report assessments. The authors report on newer research comparing dynamic grip strength with static grip strength and raise the question of which more accurately represents the force used in hand function. But here the instrument used to measure grip strength was designed specifically for the research and has not yet appeared in the clinic. In summary, the authors raise important questions concerning our measurements of grip strength and how we use this information. Further studies are required to provide knowledge regarding the usefulness of grip strength as an overall indicator of hand function.