2011 Annual Conference

Ferro Emerenciana

Using a hand-held dynamometer (HHD) provides a way to quantify muscle strength but reliability of measurements has been problematic when testing large muscle groups. Stabilization straps to secure the HHD have been used to remove tester strength as a source of error when measuring large muscle groups but a comparison of muscle strength values obtained using a HHD with and without a stabilization strap has not been studied. The purposes of this study were: 1) to determine the intra-and inter-tester reliability of an electronic HHD (MicroFet) with and without a stabilization strap when measuring quadriceps and hamstring strength, and 2) to compare quadriceps and hamstring strength values obtained using a HHD with and without a stabilization strap. We hypothesized that intra- and inter-tester reliability would be improved with a strap, and that muscle strength values measured with a strap would be greater than when measured without a strap.

30 men and women (Mean age: 37.57±16.15 years).

2 trained entry-level students of physical therapy measured participants’ quadriceps and hamstring strength in the seated position using the same test procedures. Each of the testers performed the tests under 2 conditions: 1) securing the HHD to the lower leg just proximal to the medial and lateral malleoli on the anterior aspect for knee extensors, and posterior aspect for knee flexors, using a strap affixed to an immoveable object, and 2) stabilizing the HHD manually in the same locations as for condition 1. Two trials were performed for each test condition and the order of testing under the 2 conditions randomized. One tester repeated the tests under both conditions after a 20 min rest to assess intra-tester reliability.

Data was analyzed using the 15.0 version of SPSS for Windows (SPSS Inc., Chicago, IL).  Descriptive statistics was calculated for the subject’s age, height, weight, and lower muscle strength values. An analysis of variance (ANOVA) was conducted using repeated measures of lower extremity values in order to calculate an intraclass correlation coefficient (ICC). ICC(3,2), ICC (2,2) values for Q-angle measurements was calculated to asses intra-tester and inter-tester reliability, respectively. A dependent t-test was used to compare differences between lower extremity muscle values using an electronic dynamometer with and without a stabilization strap.  An alpha level of .05 was used for this test in the analysis of each research.

Intra-tester reliability for measuring knee flexion and extension using a HHD with strap stabilization was excellent (ICC_3,2 =.98 and .98, respectively). Intra-tester reliability of measurements taken without strap stabilization for knee flexion and extension was also excellent (ICC_3,2 = .97 and .98, respectively). Inter-tester reliability for measuring knee flexion and extension using the HHD with a strap was good (ICC_2,2 =.90  and .93), while inter-tester reliability without a stabilization strap was also excellent  for knee flexion (ICC_2,2 = .93) but considerably lower  for knee extension  (ICC_2,2 =.76).  A dependent t-test showed a significant difference between hamstring strength values when taken with and without a strap (t= 2.16, p =0.039). It also showed a significant difference between quadriceps strength values obtained with and without a stabilization strap (t= 5.11, p<.001).

An electronic HHD (MicroFet) can be used effectively by a single tester to measure quadriceps and hamstring strength with or without a stabilization strap. When different testers are used however, a strap is needed to get consistent measures.

Use of stabilization straps effectively removes variability of measures due to tester strength and improved stabilization of the testing device results in higher strength values when large muscles are tested.