## 4 Discussion
As evident when interpreting by taking the SDC% value into account, there are some differences between the two measurements and the two devices, and between the strength measurements of both the flexor and extensor muscles. Although there are some differences in the measured parameters, the values of the parameters obtained from at least 89.2% of them fall within the 95% agreement limits considering the parameters mentioned above; our findings demonstrate the intra and inter-rater reliability of a well-used and a less-used IsoMed-2000 dynamometer for knee flexion and extension peak torque measurements in a concentric test in athletes. There is no information about the usage time of these dynamometers and how muscle strength measurement is affected. Our hypothesis was that even if isokinetic dynamometers are the gold standard, the usage time will affect the measurement outputs of the dynamometers. As a result of this study, the hypothesis that the muscle strength measurement of isokinetic dynamometers will change with the usage time has not been accepted. We were not able to find previous studies that compared torque values obtained through isokinetic tests performed in the same isokinetic dynamometers with different usage times. This is the first study using the same brand and model isokinetic dynamometer with different usage time for knee flexion and extension PT in athletes to investigate the usage time effect on effectiveness of dynamometers in measuring muscle strength. Data on the reliability between the test and retest were reliable when knee flexion and extension were performed at 60\({}^{\circ}\)/s and 180\({}^{\circ}\)/s; for both old and new dynamometers, the intra-rater reliabilities of the eight measures were good (ICC = 0.516-0.928). These results are consistent with the literature, and we think that the fact that the individuals included in our study were athletes and that these athletes were tested twice a year with isokinetic dynamometers affects the coefficient of compliance because it is stated that getting used to the dynamometer and the test will affect the reliability of the tests [11]. It is indicated in the literature that isokinetic concentric knee extensor and flexor strength variables were reliable when measured by the same examiner in asymptomatic subjects [27; 28]. We think that the good reliability of the study was due to the fact that both the evaluation of the muscle strength of asymptomatic athletes and the strength measurements were carried out by the same physiotherapist. Data on the reliability between the two dynamometers were also reliable when performing knee flexion and extension, showing values indicating good reliability for both trials. For the two trials, the inter-rater reliabilities of the eight measures are good (ICC = 0.519-0.915). We were not able to find studies that compare the same dynamometers, but we were able to find four previous studies that compared the torque values obtained through isokinetic tests performed in the Biodex and Cyhex dynamometers [3; 29; 30; 31]. Additionally, we found a study investigating the intermachine reliability of the Cyhex 6000 and the Cyhex II [32]. Although the isokinetic dynamometers tested in these studies were different from ours, these were the only investigations enabling a close comparison with the present study. In these studies, the concentric PT of the knee extensor and knee flexor muscles were evaluated at angular velocities of 60\({}^{\circ}\)/s, 180\({}^{\circ}\)/s and 240\({}^{\circ}\)/s [3; 29; 30; 31]. These previous studies found reliable values for knee extensor and knee flexor concentric tests between two different dynamometers, and the relative reliability was consistent with our results [3; 29; 30; 31]. There are different findings in these studies comparing the maximal knee extensor and knee flexor test results of the Biodex and Cyhex dynamometers. For example,while in one study the PT values obtained from Biodex and Cyhex are similar [3], in another study, the PT values obtained in Biodex are higher than Cyhex [31].