Isometric knee extension force measured using a handheld dynamometer with and without belt-stabilization

Although evidence suggests that tester strength limits the magnitude of isometric force that can be measured using a handheld dynamometer (HHD), previous studies have not investigated the actual limits of force magnitude that can be measured by trained testers when a belt is or is not used to stabilize the dynamometer. Therefore, the primary aims of this study were to determine: 1) the magnitude of knee extension forces that could be measured with a HHD with and without belt-stabilization and 2) the relationship between tester characteristics and knee extension strength measured with and without belt-stabilization. The characteristics of 20 trained testers (10 men, 10 women) were determined. Thereafter, they measured isometric knee extension strength using the MicroFET HHD with and without belt-stabilization. Paired t-tests were used to compare maximal knee extension forces under two conditions. Pearson productmoment correlations were calculated to determine the relationship between tester characteristics and knee extension forces measured under the two conditions. Knee extension forces (Newtons) measured using the HHD without belt-stabilization (470.6±179.8) were significantly lower (t-7.968, p<0.001) than those measured with belt-stabilization (866.9±131.7). Pearson correlations between tester characteristics and knee extension forces measured with no belt-stabilization were all statistically significant (p≤0.002); however, the correlations were not statistically significant under the belt-stabilization condition. The forces that can be measured with a HHD are higher than those suggested by previous researchers. By rectifying limitations imposed by tester strength, use of a belt allows very high knee extension forces to be measured.