I was wondering if you had any information on the hand grip strength assessment in regards to its validity and reliability and also the interpretation of its results. I found it is used quite a bit in corporate health settings, but I would like to find out how good it actually is and what exactly it is testing. Thanks!
Hand grip strength and pinch strength assessments are two useful evaluations that can be utilized for a variety of reasons. Determining one’s hand strength is necessary to conclude whether surgical or treatment procedures performed were successful. These tests can also be used to decide when someone is ready to safely return to work after an injury, to set realistic strength goals and to compare one’s grip strength to other people in the same age bracket. Questions that arise are just how reliable and valid are these tests and what methods and instruments are best to use. A large study conducted by Virgil Mathiowetz, MS, OTR and associates at the University of Wisconsin-Milwaukee was conducted recently to try to answer these questions.
Hand grip strength tests have been found to be reliable and valid by Mathiowetz, as well as numerous other studies, provided certain measures are followed. First, standardized arm positions (which do not currently exist) and instructions should be used. The American Society of Hand Therapists recently brought attention to the fact that the position of the upper extremity might make a difference in grip strength test scores. Studies by Kraft and Detels and Pyrce support this theory by concluding that grip scores were less at 15 degrees of ulnarflexion. The Hand Therapists suggested a seated position with the shoulder adducted in neutral rotation and a 90-degree flexion of the elbow with the wrist and forearm also in a neutral position.
The study by Mathiowetz and associates discovered that the highest test/retest validity occurred when the mean of three trials was used. This study as well as many others also found that the Jamar dynameter was the most accurate instrument to use for measuring grip strength. The Martin Virgometer is another common hand device that is utilized primarily for arthritic patients since it has a soft handle.
The Osco pinch meter is the type of pinch strength instrument that was used in the past, particularly in a large study published by the Keller group in 1971. The Osco meter is no longer available commercially, however, and the new type of pinch meter used, the B & L gauge, has been found to give higher readings. Mathiowetz and associates also found the B & L gauge and the Jamar dynameter to have the highest calibration accuracy of the instruments tested.
Other measures that should be adhered to in order to have valid hand strength assessments include the following:
- Compare scores obtained to appropriate age and sex categories for interpretation.
- Check the calibration of instruments used regularly.
- Use the same instrument for pre and post testing.
Some interesting factors exist that should be taken into account when interpreting hand strength scores. For example, Mathiowetz and associates found that males had similar hand strength scores as the males in the Keller study. However, females in the Mathiowetz study had significantly higher scores than the Keller study females, especially in the 20 to 54 year old age bracket. It can be theorized that the higher scores are due to the changing sex roles in our society. However, further studies would have to be done to make a definitive conclusion.
Males and females in the Mathiowetz study had higher pinch test scores than the ones in the Keller study. One might conclude that this means people’s pinch strength has increased since 1971. If this were the case, however, similar increases would be expected from hand grip strength tests. Since this did not happen, the increased pinch test scores are most likely due to the new pinch meter giving higher readings than the Osco meter used in the Keller study.
Overall, hand grip strength assessments seem to be valid tests and are beneficial in evaluating the success of surgical or treatment procedures. However, some conflicting results exist in studies regarding certain aspects of the assessments. One example is a study done by Christine M. McAniff and Richard W. Bohannon. They found that grip strength tests were valid when comparing one’s scores to published norms. They found little support, though, when using the scores to predict length of stay for rehab patients as well as their functional independence. More research studies are needed.
- Matiowetz V. Weber K Volland G Kashman N. Reliability and validity of hand strength evaluation J Hand Surg 9A:222 – 1994.
- Kraft GH. Detel. PE: Position of function of wrist: Arch Phys Med Rehabil 53:272:225. 1972.
- Pyrce JC: Wrist position between neutral and ulnar deviation that facilitates maximum power grip strength. J Biomechanics 13: 505511 – 1980.
- Keller M. Frost J. Silberberg N Iverson 1. Cummings R. Hand Strength dexterity. AM J Occup Ther 25:7743. 1971.
- McAniff C. Bohannon R. J of Phys Ther Sci Vol. 14, No. 1 41-46 – 2002.