Abstract
This study sought to assess the reliability and comparability of two custom-built isokinetic dynamometers (Model A and Model B) with the gold-standard (Humac Norm). The two custom-built dynamometers consisted of commercially available leg extension machines attached to a robotically controlled resistance device (1080 Quantum), able to measure power, force and velocity outputs. Twenty subjects (14m/6f, 26±4.8yr, 176±7cm, 74.4±12.4kg) performed concentric leg extensions on the custom-built dynamometers and the Humac Norm. Fifteen maximal leg extensions were performed with each leg at 180° s-1, or the linear equivalent (~0.5m s-1). Peak power (W), mean power (W), and fatigue indexes (%) achieved on all three devices were compared. Both custom-built dynamometers revealed high reliability for peak and mean power on repeated tests (ICC>0.88). Coefficient of variation (CV) and standard error of measurement (SEM) were small when comparing power outputs obtained using Model A and the Humac Norm ( CV = 9.0%, SEM = 49W; peak CV = 8.4%, peak SEM = 49W). Whereas, Model B had greater variance ( CV = 13.3% SEM = 120W; peak CV = 14.7%, peak SEM = 146W). The custom-built dynamometers are capable of highly reliable measures, but absolute power outputs varied depending on the leg extension model. Consistent use of a single model offers reliable results for tracking muscular performance over time or testing an intervention.
Highlights
The quantification of muscular strength and endurance is important in clinical testing [1,2], athletic capacity assessment [3,4], and broadly within human research in the exercise sciences [5,6]
The primary focus of the current study is to demonstrate that a custom-built isokinetic dynamometer, which is reliable as the gold-standard Humac Norm and could be employed for human physiology research, could be created using commercially available exercise equipment
The major finding of the present study was pairing of single-joint leg extension machines with the 1080 Quantum (Model A and Model B) showed strong consistency of test-retest (A1- A2; B1-B2) power outputs
Summary
The quantification of muscular strength and endurance is important in clinical testing [1,2], athletic capacity assessment [3,4], and broadly within human research in the exercise sciences [5,6]. Reliable and valid measures are required for the assessment of standardized test values with normative data, to track changes over time, and to interpret these effects with reference to a significant and meaningful change. The power a muscle group generates can be quantified throughout its full range of motion by employing an accommodating resistance to a standardized contraction velocity [5,7,8]. Isokinetic dynamometry provides a highly reproducible measure of neuromuscular performance in both health and disease [9].
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