Measurement of Grip Strength: Validity and Reliability of the Sphygmomanometer and Jamar Grip Dynamometer

Abstract

Quantitative measurement of grip strength is an important variable when plotting the progress of a hand-injured patient. When utilizing traditional commercially available apparatuses, obtaining meaningful grip strength measurement in these subjects is frequently difficult due to severe deformity, high tissue sensitivity, and low levels of force generated. The purpose of this study was to measure hand grip strength using two instruments having different physical characteristics and units of measurement to determine the reliability of repeated measures with each instrument. Additionally, validity of the sphygmomanometer for strength measurement was established through comparison with the values obtained from measurements using the research-validated Jamar dynamometer. Twenty-nine right hand dominant female college-age subjects volunteered to perform hand grip strength testing. Measurements were taken with a sphygmomanometer and a Jamar dynamometer while utilizing standardized measurement procedures. A Spearman Rho correlation coefficient test utilized in measuring within-instrument reliability showed a high correlation for each instrument at .85 for the sphygmomanometer and .82 for the Jamar dynamometer. Construct validity testing performed to determine validity of the measurements by the sphygmomanometer compared with the Jamar dynamometer produced a .75 correlation. A formula for conversion of the sphygmomanometer scores into Jamar units was developed to enhance reporting of sphygmomanometer scores utilizing the Jamar standard. The study showed that the sphygmomanometer and Jamar dynamometer exhibit good within-instrument reliability. Validity of the sphygmomanometer as a grip measurement device is acceptable and reportable using the conversion formula developed. Therefore, it can be utilized with confidence as essentially equal to the Jamar unit for grip strength measurement. J Orthop Sports Phys Ther 1992;16(5):215-219.