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Reproducibility of peak moment for isometric and isokinetic knee extension exercise



Accurate measurements of muscular performance are important for diagnostics, for example during rehabilitation after traumatic injuries but also in competitive sports. For these purposes, dynamometric devices are widely used and considered the gold standard for muscle strength testing. However, few previous studies have tested the reproducibility of peak moment (PM) at velocities close to the maximum device capability, and in general, reproducibility results cannot be transferred to other devices or test protocols. The purpose of this study was to evaluate the reproducibility of PM for different isometric and isokinetic knee extension exercises using the IsoMed 2000.


Thirty subjects volunteered in three repeated test sessions, including isometric knee extension (100° and 140° knee angle) and isokinetic knee extension (30°/s and 400°/s). Statistical analysis for comparison of sessions two and three included paired sample t-test, calculation of intraclass correlation coefficient (ICC) and standard error of measurement (SEM). Additionally, Bland Altman statistics and corresponding plots were created.


A significant difference between sessions in PM was found for isometric knee extension in one leg (140° left). Reproducibility was high for all conditions with ICC ranging from 0.964 to 0.988 and SEM in the range of 7.6 to 10.5 Nm. Bland Altman statistics revealed a bias between − 7.3 and 0.7 Nm.


Reproducibility of PM using the IsoMed 2000 was good after an initial familiarization trial with high values of relative reproducibility. Absolute reproducibility can be interpreted as appropriate for most common practical applications.

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Accurate measurements of muscular performance are important for diagnostics and for detecting changes in different settings. For these purposes, isokinetic dynamometry (introduced in the 1960s) is still widely used in numerous conditions and is considered the gold standard in muscle strength testing [1, 2]. Common use cases are, for example, during the rehabilitation process after traumatic injuries or to simulate different movement velocities of activities to improve the training effect but also for performance diagnostics in competitive sports [3]. In addition, the topic of interlimb strength asymmetries is of great interest, with a special focus on the prevention of injuries [4,5,6,7,8,9,10]. All of these issues are commonly investigated using dynamometric devices.

In the past, several studies that examined the reproducibility of dynamometric findings focused on the knee joint [11,12,13,14,15,16,17,18,19,20,21,22]. However, it is very difficult to generalize from one reproducibility study to another due to different devices, test-protocols and subject-groups. For example, Sole, Hamrén [23] examined the reproducibility for concentric and eccentric knee extension and flexion at 60°/s using a KinCom dynamometer. Dirnberger, Kösters [24] tested the reproducibility using another device and added a velocity of 120°/s to their protocol. Van Tittelboom, Alemdaroglu-Gürbüz [25] recently tested the reliability in children for isokinetic knee (and hip) flexion and extension at 60 and 90°/s. Dirnberger, Wiesinger [26] and Maffiuletti, Bizzini [27] are some of the few that tested knee extension in an isometric condition, with knee angles of 90° and 120°, respectively. In general, most of these studies indicate good reproducibility in measuring maximum muscular knee performance. The intraclass correlation coefficient (ICC) was > 0.9 in all these studies except Van Tittelboom, Alemdaroglu-Gürbüz [25], who found ICCs in the range of 0.59–0.87. This study also revealed the highest standard error of measurement (SEM) ranging from 15.7–22.8%, while the other studies found SEM < 10%.

For the current study, the IsoMed 2000 dynamometer was used. This dynamometer is capable of testing velocities up to 560°/s. To the best of the authors’ knowledge, there is currently only one study examining the reproducibility using this device at slow velocity [28] and no studies that used a velocity somewhere close to the maximum capability of the device. In addition, most previous studies that examined isometric contractions did this at only one joint angle. That said, there is currently a knowledge gap regarding the reproducibility of peak moment for very slow and very fast velocities and for different isometric joint angles when using this device.

The aim of this study was therefore to determine the reproducibility of PM for maximum isometric and isokinetic knee extension at two different joint angles (100° and 140°) and at very slow (30°/s) and very fast (400°/s) velocities using the IsoMed 2000 dynamometer.



Thirty subjects (25 male, 5 female; mean (SD): stature 179.4 (8.4) cm; body mass 76.0 (9.9) kg; age 30.6 (8.2) years) with no history of orthopaedic lower extremity pathology volunteered to participate in this study. Before entering the study, all subjects were physically active on a recreational level but had no previous experience in isokinetic exercise. For consistent testing conditions, subjects were instructed not to engage in vigorous physical activity for 48 h, ingestion of caffeine for 12 h, and consumption of food for 3 h prior to each test. Before the first visit to the laboratory, subjects were informed about the benefits and risks of participating in the study. Written informed consent was provided by all subjects, and they were advised that withdrawal from the study is possible at any time. The study conformed to the Declaration of Helsinki [29] and was approved by the local research ethics board at the University of Applied Sciences Wiener Neustadt on the 5th of April 2021 (approval nr RB20210405013).


All tests were conducted using an IsoMed 2000-dynamometer (D. & R. Ferstl Gmbh, Hemau, Germany) in combination with the manufacturer’s unilateral knee attachment. The device was calibrated before each session according to the manufacturer’s instructions. Data recording was performed at a sampling rate of 200 Hz using the manufacturer’s computer software IsoMed analyze SP3-i51.


Subjects were tested in three identical sessions. As several studies recommend a familiarization trial [24, 26, 30,31,32,33], the first session was set to accommodate the participants to the device and the measurement procedure and was not included in further analysis. Tests were typically conducted 72 h apart, with a minimum of 48 h between tests, to ensure sufficient recovery between trials. Subjects were tested at the same time of day (± 1.5 h), and all tests were conducted by the same examiner to minimize possible influences from diurnal variations and inter-tester variability.

Before each session, subjects completed a standardized 10-min general warm-up. Immediately after the general warm-up, subjects were placed on the adjustable dynamometer chair with the backrest at 85° (0° = fully extended) and in a way that the popliteal fossa of the tested leg ended up with the frontal edge of the seat. The knee’s rotational axis was aligned with the dynamometer’s mechanical axis using a laser pointer, with the lateral femoral epicondyle representing a bony reference point. Adjustable straps and pads were used to achieve additional stabilization and minimize errant body movements of the subjects. Fixation included the shoulders, hip, and femur with the objective of isolating the movement of the knee joint. In addition, subjects were instructed to grip the side handles of the device with their hands. At a position of 90° knee flexion, the dynamometer lever arm and the corresponding distal shin pad were attached approximately 2.5 cm superior to the lateral malleolus using a strap. The range of motion for the knee joint was set to 90–170° (180° = fully extended). After proper placement of the subjects, individual settings were recorded by the integrated software to guarantee identical positioning in every session.

Each session consisted of isometric and isokinetic knee extensions that were measured in two conditions each and for both legs. The starting leg was randomly assigned; Starting with the right vs. starting with the left leg was evenly distributed throughout the subject group. For isometric measurements, the knee joint was fixed at knee angles of 100° (Iso100) and 140° (Iso140), and isokinetic measurements were conducted at angular velocities of 30°/s and 400°/s. The slower velocity was tested prior to the faster velocity as recommended elsewhere [34]. Initial position was achieved passively and all isokinetic measurements were completed as discrete movements in a single direction [35]. The order of tests was Iso100, Iso140, 30°/s, 400°/s, and remained the same throughout all sessions.

Prior to each condition, subjects performed a submaximal specific warm-up on the device to become accustomed to the requirements of each test. This specific warm-up consisted of 10 repetitions at an intensity corresponding to approximately 50% of maximum voluntary contraction followed by 3 repetitions at an intensity corresponding to approximately 80% of maximum voluntary contraction. After this specific warm-up, subjects received a 3-min break where the procedures for the following condition were explained via standardized instructions.

For every test condition, participants completed a minimum of three repetitions. However, additional repetitions were applied as long as PM continued to improve. All of the participants reached their PM within a maximum of five repetitions. Before each repetition, subjects received 3-min of passive rest to ensure sufficient recovery. To ensure maximum effort, visual feedback was provided on a screen in front of the participant and additional strong verbal encouragement was provided by the examiner [36, 37]. After each testing-condition, the dynamometer’s position was adapted for the other leg or the following condition.

Statistical analysis

The repetition with the highest PM for each condition was selected [38, 39] from each session and used for analysis. Descriptive data are presented as mean (SD). The assumption of normality was verified using Shapiro-Wilk test.

Differences between PM were assessed with paired sample t-tests. Relative reproducibility was assessed with the two-way random effect ICC [40, 41] and calculated and interpreted according to Vincent [42]. Those recommendations consider an ICC over 0.9 as high, between 0.8 and 0.9 as moderate, and below 0.8 as low. For evaluation of absolute reproducibility, the SEM was calculated using the formula \(SEM= SD\times \sqrt{\ 1- ICC}\) [43, 44]. In addition, the SEM% was calculated, defined as SEM/(mean of measurements from sessions) * 100. To identify the level of agreement between sessions, Bland-Altman statistics ±95% limits of agreement (LoA) were calculated and corresponding plots were created for visual presentation of individual results [45].

Statistical analyses were performed using the software package IBM SPSS Statistics for Windows, V.28.0 (IBM Corp., Armonk, N.Y., USA). Figures were created using GraphPad Prism V.9.3 for Windows (GraphPad Software, San Diego, CA, USA). The level of significance was set at p < 0.05.


PM was significantly higher (+ 7.2 Nm) during the third session for the Iso140 condition in the left leg (t(29) = − 2.78, p = 0.01). No other significant differences in peak moment between sessions were observed for any condition (Table 1).

Table 1 Mean (SD) for peak moment measurements as well as p-values for comparison of sessions

The ICC indicated high values of relative reproducibility, ranging from 0.964 to 0.988 (95% CI 0.921 to 0.994). Absolute reproducibility expressed as SEM and SEM% was 7.6 to 10.5 Nm and 2.8 to 7.7%, respectively (Table 2).

Table 2 Relative and absolute reproducibility statistics for comparison of peak moment from sessions 2 and 3

Bland-Altman plots for isometric and isokinetic knee extension illustrated a random relationship between the individual differences and the averages of sessions (Figs. 1 and 2). The bias, which represents the average difference between sessions (Table 3), ranged from − 7.3 to 0.7 Nm (95% LoA from − 46.3 to 37.3 Nm), with a negative value indicating that session three had a higher value than session two.

Fig. 1
figure 1

Bland-Altman plots – differences between session two and session three plotted against the means. Differences between session two and session three plotted against the means of session two and session three for A left leg isometric extension at 100° knee angle; B right leg isometric extension at 100° knee angle; C left leg isometric extension at 140° knee angle; and D right leg isometric extension at 140° knee angle

Fig. 2
figure 2

Bland-Altman plots – differences between session two and session three plotted against the means. Differences between session two and session three plotted against the means of session two and session three for E left leg isokinetic extension at 30°/s; F right leg isokinetic extension at 30°/s; G left leg isokinetic extension at 400°/s; and H right leg isokinetic extension at 400°/s

Table 3 Bias and 95% LoA for comparison of sessions 2 and 3 received from Bland-Altman calculations

Discussion and implications

The purpose of this study was to evaluate the reproducibility of peak moment during maximum isometric and isokinetic knee extension using the IsoMed 2000 dynamometer. In general, the results suggest a high reliability of peak moment within the conditions of the current study. However, reliability results for a specific test have to be interpreted individually, according to the analytical goals of the test [43].

A possible limitation of this study was the small female sample size. The aim of this study was to gain insights into the reproducibility of PM within human adults. Therefore, we recruited a mixed gender subject group and pooled the dataset. Unfortunately, only five female volunteered for participation in this study. This could possible cause problems regarding homogeneity of the dataset. However, deleting the female dataset did not have a dramatic effect on homogeneity and therefore we did not delete their data from this study.

An additional possible limitation is the fact that we did not calculate an optimal sample size for our study. Instead we aimed for the maximum number of subjects that were available within the scheduled time-period of this study. All subjects of our study were physically active on a recreational level but did not have any previous experience in isokinetic exercise. That said subjects with previous experience in isokinetic exercise or on a higher performance level could possibly obtain other results.

An important note is that we used the first session as a familiarization session, as recommended by several authors [24, 26, 30,31,32,33]. The main goal of our study was to determine the reproducibility of peak moment (after initial familiarization). Therefore, we analysed and compared the values for peak moment from session two and session three and did not report the values from the initial familiarization session.

We found no significant difference between sessions two and three, except for Iso140 in the left leg. This finding is similar to Impellizzeri, Bizzini [46], who also found a systematic time effect in one condition of the left leg. However, Impellizzeri, Bizzini [46] detected a significant difference for concentric extension at 180°/s. A possible reason for this identified difference in the left leg could be leg dominance, though this was not analysed in our study. Therefore, the exact reason for the significant difference in only one condition of the left leg remains unclear.

Generally, our results show very good reproducibility of peak moment using the IsoMed 2000 after an initial familiarization. Regarding relative reproducibility we found ICC values > 0.964 with 95% CI of 0.921 and higher. Between all the conditions of our protocol, we detected only small differences in ICC. Therefore the relative reproducibility can be estimated as high for all conditions in this study, according to the recommendations of Vincent [42].

According to Caruso, Brown [47], the excellent levels of reproducibility under test-retest conditions seem to be unique for the knee joint.

When comparing our results to previous studies, slightly higher results were observed. The ICC values in our study are higher than those obtained in a similar study by Kues, Rothstein [48], who tested isometric knee angles of 120° and 140°. Our results also show higher ICC than in the study of Alt, Knicker [28]. These authors found values < 0.9 for the comparison of T2-T3 in isokinetic knee extension. However, in their study subjects were tested in a supine position that was different from the seated position in our study. Our results for ICC are similar to those of Dirnberger, Kösters [24], who found ICC values in the range of 0.976–0.984 for concentric isokinetic knee extension at velocities of 60°/s and 120°/s, respectively.

In our study, we found better relative reproducibility (ICC) for the faster velocity which is contrary to previous research results. For example, Brown, Whitehurst [49] tested a broad range of different isokinetic velocities from 60 to 450°/s. Regarding knee extension, they found a trend for better reproducibility at slower velocities. The same was true in the study of Fagher, Fritzson [50] who also found better relative reproducibility for slower velocity. It should be noted, however, that the participants in their study were children aged 8 to 10 years, which could impair direct comparisons with adults.

Regarding absolute reproducibility, almost all obtained values in our study are below 10 Nm, with only Iso100 for the left leg (10.0 Nm) and 30°/s for the right leg (10.5 Nm) being just slightly higher (Table 2). When comparing the SEM (Nm) for slow and fast isokinetic velocities, it was lower for 400°/s compared to 30°/s. However, calculating the SEM% revealed values between 2.8 and 4.4% for all isometric conditions and for 30°/s. At 400°/s the SEM% was considerably higher (7.6 and 7.7% for the right and left leg, respectively). This is almost twice that of most of the other conditions and would indicate inferior reproducibility for the faster velocity of 400°/s. These results for absolute reproducibility are similar to those found by Dirnberger, Wiesinger [26]., although the authors in this study tested only one leg. In contrast to these results that found better reproducibility for slower velocity, other authors [24, 26, 27, 48, 51] have found better reproducibility for faster velocities. On the other hand, Impellizzeri, Bizzini [46] found no clear tendency regarding velocity. The authors reported the lowest SEM% for 180°/s, followed by 60°/s. For 120°/s, the SEM% was the highest of the three conditions in this study. However, the difference between the three tested velocities of their protocol was small, and the range between the slowest and the fastest velocity regarding SEM% was just 0.8%.

Therefore, based on current available studies and the results of this study, there is inconsistency regarding a comparison between reproducibility results of different velocities for isokinetic knee extension. That points out that generalizing reproducibility results is difficult and that different velocities lead to partly divergent reproducibility.


This study investigated the reproducibility of peak moment obtained from different isometric and isokinetic knee extension exercises using the IsoMed 2000 dynamometer. The findings suggest that after an initial familiarization trial, peak moment can be measured at a level that is considered excellent for most common applications. Practitioners should aim for a familiarization trial in each angle and velocity when doing isometric or isokinetic exercise to obtain reliable results.

Availability of data and materials

The datasets used and analysed during the current study are available from the corresponding author on reasonable request.



intraclass correlation coefficient


isometric, 100° knee angle


isometric, 140° knee angle


limits of agreement


peak moment


standard error of measurement


  1. Stark T, Walker B, Phillips JK, Fejer R, Beck R. Hand-held dynamometry correlation with the gold standard isokinetic dynamometry: a systematic review. PM&R. 2011;3(5):472–9.

    Article  Google Scholar 

  2. Seven B, Cobanoglu G, Oskay D, Atalay-Guzel N. Test–retest reliability of isokinetic wrist strength and proprioception measurements. J Sport Rehabil. 2019;28(7):1–6.

  3. Baltzopoulos V, Brodie D. Isokinetic dynamometry. Appl limitat Sports Med. 1989;8(2):101–16.

    Article  CAS  Google Scholar 

  4. Cowley HR, Ford KR, Myer GD, Kernozek TW, Hewett TE. Differences in neuromuscular strategies between landing and cutting tasks in female basketball and soccer athletes. J Athl Train. 2006;41(1):67–73.

    PubMed  PubMed Central  Google Scholar 

  5. Hewett TE, Stroupe AL, Nance TA, Noyes FR. Plyometric training in female athletes: decreased impact forces and increased hamstring torques. Am J Sports Med. 1996;24(6):765–73.

    Article  CAS  PubMed  Google Scholar 

  6. Jones PA, Bampouras TM. A comparison of isokinetic and functional methods of assessing bilateral strength imbalance. J Strength Cond Res. 2010;24(6):1553–8.

    Article  PubMed  Google Scholar 

  7. Knapik JJ, Bauman CL, Jones BH, Harris JM, Vaughan L. Preseason strength and flexibility imbalances associated with athletic injuries in female collegiate athletes. Am J Sports Med. 1991;19(1):76–81.

    Article  CAS  PubMed  Google Scholar 

  8. Mangine GT, Hoffman JR, Gonzalez AM, Jajtner AR, Scanlon T, Rogowski JP, et al. Bilateral differences in muscle architecture and increased rate of injury in national basketball association players. J Athl Train. 2014;49(6):794–9.

    Article  PubMed  PubMed Central  Google Scholar 

  9. Myer GD, Ford KR, Hewett TE. Rationale and clinical techniques for anterior cruciate ligament injury prevention among female athletes. J Athl Train. 2004;39(4):352–64.

    PubMed  PubMed Central  Google Scholar 

  10. Nadler SF, Malanga GA, Feinberg JH, Prybicien M, Stitik TP, DePrince M. Relationship between hip muscle imbalance and occurrence of low back pain in collegiate athletes: a prospective study. Am J Phys Med Rehabil. 2001;80(8):572–7.

    Article  CAS  PubMed  Google Scholar 

  11. Adsuar JC, Olivares PR, del Pozo-Cruz B, Parraca JA, Gusi N. Test-retest reliability of isometric and isokinetic knee extension and flexion in patients with fibromyalgia: evaluation of the smallest real difference. Arch Phys Med Rehabil. 2011;92(10):1646–51.

    Article  PubMed  Google Scholar 

  12. Brunner-Althaus C, de Bruin ED. Die Zuverlassigkeit des isokinetischen Knie Kurzprotokolls von Swiss Olympic. Schweiz Z Sportmed Sporttraumatol. 2006;54(3):96–100.

    Google Scholar 

  13. Chan JPY, Krisnan L, Yusof A, Selvanayagam VS. Maximum isokinetic familiarization of the knee: implication on bilateral assessment. Hum Mov Sci. 2020;71:102629.

    Article  PubMed  Google Scholar 

  14. Collado-Mateo D, Dominguez-Muñoz FJ, Charrua Z, Adsuar JC, Batalha N, Merellano-Navarro E, et al. Isokinetic strength in peritoneal dialysis patients: a reliability study. Appl Sci. 2019;9(17):3542.

    Article  Google Scholar 

  15. de Oliveira MPB, Calixtre LB, da Silva Serrão PRM, de Oliveira ST, de Medeiros Takahashi AC, de Andrade LP. Reproducibility of isokinetic measures of the knee and ankle muscle strength in community-dwelling older adults without and with Alzheimer’s disease. BMC Geriatr. 2022;22(1):1–11.

    Article  Google Scholar 

  16. Hartmann A, Knols R, Murer K, De Bruin ED. Reproducibility of an isokinetic strength-testing protocol of the knee and ankle in older adults. Gerontol. 2009;55(3):259–68.

    Article  Google Scholar 

  17. Hibbert JE, Kulas AS, Rider PM, Domire ZJ. Practice day may be unnecessary prior to testing knee extensor strength in young healthy adults. Int Biomech. 2020;7(1):58–65.

    Article  PubMed  PubMed Central  Google Scholar 

  18. Lienhard K, Lauermann S, Schneider D, Item-Glatthorn J, Casartelli N, Maffiuletti N. Validity and reliability of isometric, isokinetic and isoinertial modalities for the assessment of quadriceps muscle strength in patients with total knee arthroplasty. J Electromyogr Kinesiol. 2013;23(6):1283–8.

    Article  CAS  PubMed  Google Scholar 

  19. Lund H, Søndergaard K, Zachariassen T, Christensen R, Bülow P, Henriksen M, et al. Learning effect of isokinetic measurements in healthy subjects, and reliability and comparability of Biodex and lido dynamometers. Clin Physiol Funct Imag. 2005;25(2):75–82.

    Article  CAS  Google Scholar 

  20. Symons TB, Vandervoort AA, Rice CL, Overend TJ, Marsh GD. Reliability of a single-session isokinetic and isometric strength measurement protocol in older men. J Gerontol A Biol Sci Med Sci. 2005;60(1):114–9.

    Article  PubMed  Google Scholar 

  21. Tiffreau V, Ledoux I, Eymard B, Thévenon A, Hogrel J-Y. Isokinetic muscle testing for weak patients suffering from neuromuscular disorders: a reliability study. Neuromuscul Disord. 2007;17(7):524–31.

    Article  PubMed  Google Scholar 

  22. Tuominen J, Leppänen M, Jarske H, Pasanen K, Vasankari T, Parkkari J. Test− retest reliability of isokinetic ankle, knee and hip strength in physically active adults using Biodex system 4 pro. Methods protoc. 2023;6(2):26–35.

    Article  PubMed  PubMed Central  Google Scholar 

  23. Sole G, Hamrén J, Milosavljevic S, Nicholson H, Sullivan SJ. Test-retest reliability of isokinetic knee extension and flexion. Arch Phys Med Rehabil. 2007;88(5):626–31.

    Article  PubMed  Google Scholar 

  24. Dirnberger J, Kösters A, Müller E. Concentric and eccentric isokinetic knee extension: a reproducibility study using the IsoMed 2000-dynamometer. Isokinet Exerc Sci. 2012;20(1):31–5.

    Article  Google Scholar 

  25. Van Tittelboom V, Alemdaroglu-Gürbüz I, Hanssen B, Heyrman L, Feys H, Desloovere K, et al. Reliability of isokinetic strength assessments of knee and hip using the Biodex system 4 dynamometer and associations with functional strength in healthy children. Front Sports Act Living. 2022;4:1–10.

  26. Dirnberger J, Wiesinger H-P, Kösters A, Müller E. Reproducibility for isometric and isokinetic maximum knee flexion and extension measurements using the IsoMed 2000-dynamometer. Isokinet Exerc Sci. 2012;20(3):149–53.

    Article  Google Scholar 

  27. Maffiuletti NA, Bizzini M, Desbrosses K, Babault N, Munzinger U. Reliability of knee extension and flexion measurements using the con-Trex isokinetic dynamometer. Clin Physiol Funct Imag. 2007;27(6):346–53.

    Article  Google Scholar 

  28. Alt T, Knicker AJ, Strüder HK. Factors influencing the reproducibility of isokinetic knee flexion and extension test findings. Isokinet Exerc Sci. 2014;22(4):333–42.

    Article  Google Scholar 

  29. Association WM. World medical association declaration of Helsinki: ethical principles for medical research involving human subjects. JAMA. 2013;310(20):2191–4.

    Article  Google Scholar 

  30. Nugent EP, Snodgrass SJ, Callister R. The effect of velocity and familiarisation on the reproducibility of isokinetic dynamometry. Isokinet Exerc Sci. 2015;23(3):205–14.

    Article  Google Scholar 

  31. Roth R, Donath L, Kurz E, Zahner L, Faude O. Absolute and relative reliability of isokinetic and isometric trunk strength testing using the IsoMed-2000 dynamometer. Phys Ther Sport. 2017;24:26–31.

    Article  PubMed  Google Scholar 

  32. Dirnberger J, Huber C, Hoop D, Kösters A, Müller E. Reproducibility of concentric and eccentric isokinetic multi-joint leg extension measurements using the IsoMed 2000-system. Isokinet Exerc Sci. 2013;21(3):195–202.

    Article  Google Scholar 

  33. Jenkins ND, Cramer JT. Reliability and minimum detectable change for common clinical physical function tests in sarcopenic men and women. J Am Geriatr Soc. 2017;65(4):839–46.

    Article  PubMed  Google Scholar 

  34. Wilhite MR, Cohen ER, Wilhite SC. Reliability of concentric and eccentric measurements of quadriceps performance using the KIN-COM dynamometer: the effect of testing order for three different speeds. J Orthop Sports Phys Ther. 1992;15(4):175–82.

    Article  CAS  PubMed  Google Scholar 

  35. Rothstein JM, Lamb RL, Mayhew TP. Clinical uses of isokinetic measurements: critical issues. Phys Ther. 1987;67(12):1840–4.

    Article  CAS  PubMed  Google Scholar 

  36. Miller W, Jeon S, Kang M, Song JS, Ye X. Does performance-related information augment the maximal isometric force in the elbow flexors? Appl Psychophysiol Biofeedback. 2021;46:91–101.

    Article  PubMed  Google Scholar 

  37. Karaba-Jakovljević D, Popadić-Gaćeša J, Grujić N, Barak O, Drapšin M. Motivation and motoric tests in sports. Med Pregl. 2007;60(5–6):231–6.

    Article  PubMed  Google Scholar 

  38. Perrin DH, Robertson RJ, Ray RL. Bilateral isokinetic peak torque, torque acceleration energy, power, and work relationships in athletes and nonathletes. J Orthop Sports Phys Ther. 1987;9(5):184–9.

    Article  CAS  PubMed  Google Scholar 

  39. Kannus P. Isokinetic evaluation of muscular performance. Int J Sports Med. 1994;15(S 1):S11–S8.

    Article  PubMed  Google Scholar 

  40. Shrout PE, Fleiss JL. Intraclass correlations: uses in assessing rater reliability. Psychol Bull. 1979;86(2):420–8.

    Article  CAS  PubMed  Google Scholar 

  41. Koo TK, Li MY. A guideline of selecting and reporting intraclass correlation coefficients for reliability research. J Chiropr Med. 2016;15(2):155–63.

    Article  PubMed  PubMed Central  Google Scholar 

  42. Vincent WJ. Statistics in kinesiology. Third ed. Champaign, IL: Human Kinetics; 2005.

    Google Scholar 

  43. Atkinson G, Nevill AM. Statistical methods for assessing measurement error (reliability) in variables relevant to sports medicine. Sports Med. 1998;26:217–38.

    Article  CAS  PubMed  Google Scholar 

  44. Weir JP. Quantifying test-retest reliability using the intraclass correlation coefficient and the SEM. J Strength Cond Res. 2005;19(1):231–40.

    PubMed  Google Scholar 

  45. Bland JM, Altman D. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet. 1986;327(8476):307–10.

    Article  Google Scholar 

  46. Impellizzeri FM, Bizzini M, Rampinini E, Cereda F, Maffiuletti NA. Reliability of isokinetic strength imbalance ratios measured using the Cybex NORM dynamometer. Clin Physiol Funct Imag. 2008;28(2):113–9.

    Article  Google Scholar 

  47. Caruso JF, Brown LE, Tufano JJ. The reproducibility of isokinetic dynamometry data. Isokinet Exerc Sci. 2012;20(4):239–53.

    Article  Google Scholar 

  48. Kues JM, Rothstein JM, Lamb RL. Obtaining reliable measurements of knee extensor torque produced during maximal voluntary contractions: an experimental investigation. Phys Ther. 1992;72(7):492–501.

    Article  CAS  PubMed  Google Scholar 

  49. Brown LE, Whitehurst M, Bryant JR, Buchalter DN. Reliability of the Biodex system 2 isokinetic dynamometer concentric mode. Isokinet Exerc Sci. 1993;3(3):160–3.

    Article  Google Scholar 

  50. Fagher K, Fritzson A, Drake AM. Test-retest reliability of isokinetic knee strength measurements in children aged 8 to 10 years. Sports Health. 2016;8(3):255–9.

    Article  PubMed  PubMed Central  Google Scholar 

  51. Li R, Wu Y, Maffulli N, Chan KM, Chan J. Eccentric and concentric isokinetic knee flexion and extension: a reliability study using the Cybex 6000 dynamometer. Br J Sports Med. 1996;30(2):156–60.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

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The authors would like to thank all subjects who volunteered to participate in this study.


Open access funding provided by University of Vienna. This work was supported by Gesellschaft für Forschungsförderung Niederösterreich m.b.H. under Grant number SC19–002.

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Authors and Affiliations



Conception: KW conceived and designed the research. Performance of work: MZ conducted the experiments. Interpretation and analysis of data: MZ analysed the data. MZ and KW interpreted the results of the experiments. Preparation of the manuscript: MZ drafted the first version of the manuscript. Revision for important intellectual content: MZ, AN, AB and KW were involved in the revision and approval of the final version of the manuscript. Supervision: AB supervised the study and was assisted by AN and KW as co-supervisors.

Corresponding author

Correspondence to Manfred Zöger.

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Ethics approval and consent to participate

The experiments involving human participants were reviewed and approved by the local Research Ethics Board at the University of Applied Sciences Wiener Neustadt on the 5th of April 2021 (approval nr RB20210405013). Written informed consent to participate in this study was provided by all participants before the start of the experiments.

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The authors declare no competing interests.

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Zöger, M., Nimmerichter, A., Baca, A. et al. Reproducibility of peak moment for isometric and isokinetic knee extension exercise. BMC Sports Sci Med Rehabil 15, 171 (2023).

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