Adequacy of belt-stabilized testing of knee extension strength

Tester strength can limit the forces that can be measured using a hand-held dynamometer (HHD). A solution is to use belt stabilization in conjunction with an HHD. The purposes of this study were to determine if a portable belt-stabilized HHD (BSHHD) setup was capable of measuring a broad range of isometric knee extension torques and whether isometric knee extension torques measured using a portable BSHHD system were comparable to those obtained using a Biodex isokinetic dynamometer. Participants in the study were 113 women and 71 men (14-85 years of age) community-dwelling enrollees in the National Institutes of Health Toolbox for the Assessment of Neurological and Behavioral Function. Knee extension torques measured using a BSHHD ranged from 35.0-416.0 N·m. Torques measured with the BSHHD were significantly lower (p < 0.001) than those measured using the isokinetic dynamometer (mean difference: 35.6 N·m left, 33.7 N·m right). However, the measures were highly correlated (r > 0.86, p < 0.001). Torques obtained with a BSHHD may not equal the maximum that individuals can generate, but they reflect such torques. We conclude, therefore, that a portable BSHHD setup is a viable option for measuring a wide spectrum of knee extension torques in diverse settings.