The Nicholas Hand-Held Dynamometer (HHD) has been shown to have excellent interday and intraday reliability when using the same HHD. Since clinics may have more than one HHD with which to evaluate patients, it would be of value to know if 2 identical HHDs measure the same variable consistently. The purpose of this investigation was to assess interdevice reliability of the Nicholas HHD as well as to determine its validity. Thirty healthy female subjects between the ages of 20 and 56 years (x¯ age = 28.4) were tested for hamstring strength. Three measurements of maximum hamstring contractions were obtained using the first HHD (Device A). The average of these 3 measurements was compared with the average of 3 measurements obtained after a brief rest using a second HHD (Device B). Measurements from the 2 HHDs were also compared with measurements obtained from a Kin-Com isokinetic dynamometer. The Kin-Com measurements were used as criteria to determine validity of the HHD. An intraclass correlation coefficient (ICC) calculated to determine reliability between the 2 HHDs was low (ICC = 0.58). Pearson product-moment correlation coefficients were calculated between the Kin-Com and each of the 2 HHDs. These values were 0.85 and 0.83 for Device A and B, respectively. Analysis of variance showed no significant difference between the Kin-Com and Device A but a significant difference between the Kin-Com and Device B (p<.001). Measurements obtained from 2 identical HHDs may be significantly different and should not be compared.
J Orthop Sports Phys Ther. 1994;20(6):302-306.
Key Words: muscle strength, validity, Kin-Com