Affiliations: [a] Department of Health, Physical Education and Leisure Services, University of South Alabama, Mobile, AL 36688, USA | [b] Athletic Training Department, Indiana State University, Terre Haute, IN, USA
Abstract: The BTE Dynatrac is an isotonic dynamometer in where the preset resistance determines the effort and the limb must overcome the resistance to accelerate through the ROM. Previous reliability studies of isokinetic devices do not apply to this type of dynamometer. Therefore, the purpose of this study was to assess the reliability of the BTE Dynatrac Isotonic Dynamometer using average work and power to determine whether the Dynatrac can produce consistent results under different preset loads and between exercise sessions. Twenty-nine (M = 19; F = 10) recreationally active college students underwent identical testing on three occasions. On a day before testing, peak torque was measured from a 6 s maximal voluntary isometric contraction (MVIC) at 70° of knee flexion. This value determined the preset loads used for the three isotonic testing sessions. During the isotonic sessions each subject performed six repetitions of maximal knee extensions at preset loads (20%, 40%, and 60% of MVIC) through the 90° ROM. The order of testing on each of the three nonconsecutive days was determined by using a balanced Latin Square. Average work and power were recorded and analyzed. The reliability of average power measurement was excellent regardless of the preset load (20% MVIC = 0.82; 40% MVIC = 0.83; and 60% MVIC = 0.90). The reliability of average work measurement was excellent at 60% MVIC(0.86) and 40% MVIC(0.80), but only fair at 20% MVIC(0.57). We conclude that clinicians can be confident in comparing average power measurements between sessions regardless of the preset load and for average work at the moderate to higher preset loads.
Keywords: Isotonic, Muscle contraction, Reliability, Muscle power
