The Use And Applications Of Isokinetic Dynamometer For Muscle Strength Assessment

Essay is on "Isokinetic Dynamometer" which is a modality I am using to assess the strength of the knee flexors and extensors after anterior cruciate ligament injury.

This is a part of my main dissertation topic i.e. "Will post activation potentiation have an effect on isometric muscular strength in patients with anterior cruciate ligament injury post rehabilitation?".

Following are the details on the requirements of the assignment:

Your chosen modality (method or technology) with a view to providing a critical understanding of the operation and application of that modality. The review should make reference to underlying scientific literature and historical perspectives, and provide an analytical critique into the effectiveness, strengths and possible limitations of the chosen modality.

You should, as part of your critical review, provide evidence of understanding of reliability and validity based on data collected throughout the module, or related scientific evidence.

You should also discuss the pertinence of your chosen modality in relation to other (similar) modalities, and how you intend to apply your learnings to your own research.

The Technology of Isokinetic Dynamometer

Dynamometer refers to a device that is used for the measurement of torque, force and power. Besides determining characteristics associated with torque or power of a machine that is being tested, dynamometers are also utilized with the aim of providing simulated road loading of engines or complete powertrains. They are also used or different types of activities that involve engine development such as, calibrations and detailed investigations (Thorborg, Bandholm and Hölmich 2013). An isokinetic dynamometer commonly refers to pieces of equipment that are put to use in sports and physical therapeutic contexts and often look similar to a positioning chair that is attached to machines of adjustable strength and a computer controlled unit. The device helps in the measurement of performance of a range of muscle groups. It is also used in certain complex situations that encompass sensitive force measurements of different speeds and angles. These measurements commonly incorporate fatigue, resistance, strength and torque (Edouard et al. 2013). An isokinetic dynamometer has also been identified successful in accommodating a plethora of muscle movements namely, isokinetic, isometric, and isotonic movements. The dynamometer moderates forces with the aim of preventing injury that can be attributed to its reaction against external forces, followed by a cessation of function upon stopping the applied force. The essay aims to elaborate on the application of isokinetic dynamometer in assessing the strength of knee flexors and extensors, following an anterior cruciate ligament injury.

The technology of isokinetic dynamometer accommodates several rehabilitative and evaluative approaches in the primary joints of the human body. Among all possible movements, the isokinetic dynamometer is primarily use for evaluating pronation, flexion, abduction, and other associated movements, in addition to their counter forces. Touch panels and computers help in bringing about adjustments to the speeds, forces, and ranges of motion that are specific for the patient requirements. Isokinetic movements have been found available since the 1950s (Oliveira et al. 2015). Isokinetic movement was first introduced by Hettinger and was completely in contrast with different motion forms owing to the fact that it allowed maximum contraction of muscles, throughout the complete range of motion. Measurement of muscle forces under conditions that involve constant velocity have gained popularity in recent years. This is attributed to the use of isokinetic dynamometers that deliver information on the dynamic muscle contractions. Research evidences suggest that isokinetic rehabilitative devices were first developed during the 1960s that facilitated the study of muscle’s mechanical properties under conditions that encompassed constant velocity (Baltzopoulos 2017). The modern isokinetic dynamometers have proved their efficiency in providing information on limb velocity and muscle load, which in turn has contributed to their widespread use.

Applications of isokinetic dynamometer in sports and research settings

The isokinetic dynamometer are also used frequently for studying muscular functions of the human body in research environment, principally to mainly investigate post-lesion of muscles that are present around articulation of the knees. In addition of reporting reliability and good validity, the dynamometer also facilitates the evaluation of maximum torque that is created by muscles, during endurance of movement. Evidences have also established the fact that sports practice and training lead to the development of precise musculature, which in turn is governed by the modality practiced (Hauraix, Nordez and Dorel 2013). These muscular specializations play a direct role in the development of imbalance of certain forces that are found to act dynamically and statically on the joints of the limbs, thereby resulting in modifications of articular mechanics and body posture. The resulting imbalance in the muscles also increase the risk of predisposition to performance reduction due to injury among athletes. The widespread use of isokinetic dynamometers can be attributed to its role in facilitating an objective, accurate, dynamic and reproducible assessment of muscular function (Severo-Silveira et al. 2017). This measurement is commonly achievable for all kinds of resistance that are applied to the movement, and can be easily adapted with the aim of permitting constant angular velocity throughout the entire range of muscular motion. In other words, isokinetic dynamometers optimise the load and help in the characterisation of muscular modifications that result from sports practice, thereby leading to an improvement in sports performance, specificity of training and prevention of subsequent injuries.

Some of the major advantages of isokinetic dynamometer associated exercise comprise of accommodation of resistance, safety, and muscle force analysis. Assessment of the characteristics of muscle strength at several angular velocities help in gaining a deeper understanding of the functions of knee joint. Besides the advantages provided by isokinetic dynamometry, there are a plethora of considerations that are regarded vital in the explanation of all force recordings (Undheim et al. 2015). The term "isokinetic" commonly encompasses types of contractions in the muscle, which in turn goes along with a limb movement at a constant rate. Furthermore, isokinetic exercise are also accompanied by regular stages of acceleration and deceleration. Acceleration and subsequent phases of oscillation and deceleration isokinetic exercise are found to restrict the time duration of constant velocity of exercises that involve isokinetic dynamometry (Amaral et al. 2014). Cybex and KinCom are common isokinetic dynamometers that measure muscle power by exerting a control on the velocity of movement, with the use of strain gauge force transducers.

Advantages of Isokinetic Dynamometer

A study was conducted with the aim of assessing the reliability of knee flexor and extensor muscle strength with the use of isokinetic dynamometer. It elucidated on the popularity of isokinetic dynamometers in sports and research settings for investigating the eccentric, joint and muscle and isometric strength at constant velocities. The study provided evidence for increased reliability of the ECC, CON, and ISO related muscle strength assessment with the use of REV9000 dynamometer for flexor and extensor muscles. Higher ICC was found for peak torque in left knee flexor (0.97) ECC contraction and lowest for left knee extensor ICC in ISO contraction (0.93). The results were in accordance with studies conducted earlier that also reported values of 0.97 for concentric contractions. Furthermore, the study also indicated that the peak torque reliability for right knee flexor was higher than the extensor. This finding was not consistent with those published in previous research studies. Therefore, the results established the use of isokinetic dynamometers for assessment of sports performance and improvements in training process (de Carvalho Froufe et al. 2013). The use of isokinetic dynamometers were demonstrated by another study as well that aimed to evaluate the impacts of difference in thigh circumference between knees of patients administered ACL reconstruction. The fact that anterior cruciate ligaments play a major role in anterior translation limitations of tibia formed the background of the study. It elaborated on the conduction of muscle strength tests for assessing ACL recovery, following a treatment. The findings suggested that after an ACL reconstruction surgery, it is possible to meet thigh atrophy after 28 months. Quadriceps muscle mass was also found responsible for thigh atrophy observed among the participants, regardless of the negative impacts of hamstring muscle group on atrophy of the muscles. This in turn was determined along with the manual measurements of thigh circumference. No significant differences were observed in the torque per unit volume and flexion speed of the knee flexors. Furthermore, reconstruction of the ACL with hamstring tendon was not effective on the torque power of the knee flexors and speed of flexion of the muscles (K?l?nç et al. 2015).

Upon determining the reliability and validity of isometric knee extension and flexion measurements, another study found that no significant difference existed between isokinetic dynamometry (IKD) and portable fixed dynamometry (PFD). The trial was focused on the reliability and validity of isokinetic dynamometers in the assessment of muscle strength and considered it as the gold standard, for comparison with other measures. However, the study also took into account the range of limitations of isokinetic dynamometers such as, their expensive nature, extensive training for operation, lack of portability, the fact that the machine occupies a large expanse of clinical space. Findings of the study also demonstrated similarity between the peak torques that were recorded for knee extension and flexion between the PFD and IKD. Nonetheless, noteworthy dissimilarities were recognised between the IKD and HHD. The reliability measures of the study confirmed good and high reliability for tests and retests for both PFD and IKD, during the assessment of isometric knee strength. It also elaborated on the strength of isokinetic testing that creates a provision for practitioners to deliver stabilization, while conducting the tests, in addition to providing consistent protocols for isometric strength measurements. Thus, the study established the high trustworthiness of isokinetic dynamometers (Toonstra and Mattacola 2013).

Reliability and Validity of Isokinetic Dynamometer

Upon assessing the inter-machine reliability of Cybex Humac Norm Model 770 and Biodex System 3 Pro dynamometers, no significant differences were observed between the two. The ICC values indicated high and very high rates of reproducibility for concentric, isometric and eccentric peak torque in the range of 0.88-0.92. Reliability was found to be moderate to high for agonist and antagonist ratios of strength (0.62-0.73). Furthermore, no major differences were found between CV (5.27-7.77%) and SEM (3.72-11.27 Nm) dynamometers. Thus, the results illustrated that maximal knee flexion and extension tests that were performed in Cybex and Biodex isokinetic dynamometers presented same values for peak torque (Alvares et al. 2015). Similar findings were reported by another study that evaluated the test–retest reliability and validity of trunk muscle strengths that were performed with the use of isokinetic dynamometers. Significant associations were observed between peak torque and muscle cross sectional area for all types of contraction (r = 0.74−0.85; P < 0.001). The findings also established correlation between submaximal isometric torque and EMG activity (r ? 0.99; P < 0.05) for both the flexor and extensor muscles. Mean differences between retest and test for peak torque were found to range from -3.7-3.7%, without any noteworthy mean directional bias. Therefore, the results confirmed the validity of isokinetic dynamometer related torque measurements (Guilhem et al. 2014).

The presence of weakness in the knee, hip and ankle muscles, following an ACL injury were determined by another study that provided evidence for increased hip-extensor and adductor weakness before the operation, when compared to the post-operative measures. Furthermore, knee-flexor and knee-extensor strength were found to be low in injured areas, upon comparison to preoperative and postoperative uninjured limbs. This showed consistency with previous findings that supported the presence of increased weakness in knee extensor and flexor during the postoperative time in injured limbs. Thus, knee flexors and extensors were identified as major dynamic stabilisers and weakness in the knee muscles were directly associated with joint stability (Kim et al. 2014). Upon assessing the differences between maximal knee extension in torque variability of knee extension among patient suffering from crucial ligament reconstruction, torque variability was found to be more, in addition to low scores of CAR and IKDC in the ACL-reconstruction group, when compared to the control group (p<0.05) (Thomas et al. 2013). The study elaborated on the surgical treatment that is commonly performed in individuals after they experience a disability following an ACL. The background of the study was focused on the fact that ACL-R results in changes in the motor function of the quadriceps, which in turn manifests in the form of inhibition, weakness, loss of motor control and diminished power. Torque variability was also formed a significant proportion of the IKDC scores (14.3%). Further findings of the study also emphasised on role of torque variability in predicting 21% of IKDC score variances, in combination with postsurgical months (Goetschius and Hart 2016).

Conclusion

Conclusion

To conclude, sports practice and training marks the formation of specific musculature that depends on the modality practiced. Isokinetic dynamometers have the capability of applying motor-driven external forces to the muscles as a result of eccentric loading. These also introduce a range of safety considerations that are not present with the use of passive dynamometers. Eccentric exercise have been found to create higher tension, when compared to concentric exercise and have also been implicated in suspending the onset of soreness in muscles and subsequent injury. Isokinetic dynamometers have been proved successful in specifying anticipated torque and angular velocity at the rotating joints of the knees, in the form of a function of angle and time of displacement. In other words, an assessment of the isokinetic muscle strength helps in providing essential information on the kinetic torque production that occur during a range of muscle actions, encompassing varied angular velocity. These information are then utilised for rehabilitation of muscle injuries and the recognition of specific strengths and weaknesses between the antagonist and agonist muscle group limbs. 

References

Alvares, J.B.D.A.R., Rodrigues, R., de Azevedo Franke, R., da Silva, B.G.C., Pinto, R.S., Vaz, M.A. and Baroni, B.M., 2015. Inter-machine reliability of the Biodex and Cybex isokinetic dynamometers for knee flexor/extensor isometric, concentric and eccentric tests. Physical Therapy in Sport, 16(1), pp.59-65.

Amaral, G.M., Marinho, H.V., Ocarino, J.M., Silva, P.L., Souza, T.R.D. and Fonseca, S.T., 2014. Muscular performance characterization in athletes: a new perspective on isokinetic variables. Brazilian journal of physical therapy, 18(6), pp.521-529.

Baltzopoulos, V., 2017. Isokinetic dynamometry. In Biomechanical evaluation of movement in sport and exercise(pp. 158-185). Routledge.

de Carvalho Froufe, A.C.P., Caserotti, P., de Carvalho, C.M.P., de Azevedo Abade, E.A. and da Eira Sampaio, A.J., 2013. Reliability of concentric, eccentric and isometric knee extension and flexion when using the REV9000 isokinetic dynamometer. Journal of human kinetics, 37(1), pp.47-53.

Edouard, P., Codine, P., Samozino, P., Bernard, P.L., Hérisson, C. and Gremeaux, V., 2013. Reliability of shoulder rotators isokinetic strength imbalance measured using the Biodex dynamometer. Journal of Science and Medicine in Sport, 16(2), pp.162-165.

Goetschius, J. and Hart, J.M., 2016. Knee-extension torque variability and subjective knee function in patients with a history of anterior cruciate ligament reconstruction. Journal of athletic training, 51(1), pp.22-27.

Guilhem, G., Giroux, C., Couturier, A. and Maffiuletti, N.A., 2014. Validity of trunk extensor and flexor torque measurements using isokinetic dynamometry. Journal of Electromyography and Kinesiology, 24(6), pp.986-993.

Hauraix, H., Nordez, A. and Dorel, S., 2013. Shortening behavior of the different components of muscle-tendon unit during isokinetic plantar flexions. Journal of Applied Physiology, 115(7), pp.1015-1024.

K?l?nç, B.E., Kara, A., Savas Camur, Y.O. and Celik, H., 2015. Isokinetic dynamometer evaluation of the effects of early thigh diameter difference on thigh muscle strength in patients undergoing anterior cruciate ligament reconstruction with hamstring tendon graft. Journal of exercise rehabilitation, 11(2), p.95.

Kim, W.K., Kim, D.K., Seo, K.M. and Kang, S.H., 2014. Reliability and validity of isometric knee extensor strength test with hand-held dynamometer depending on its fixation: a pilot study. Annals of rehabilitation medicine, 38(1), pp.84-93.

Oliveira, S.C.G., Oliveira, L.M., Jones, A. and Natour, J., 2015. Isokinetic assessment of ankles in patients with rheumatoid arthritis. Revista brasileira de reumatologia, 55(4), pp.318-324.

Severo-Silveira, L., Fritsch, C.G., Marques, V.B., Dornelles, M.P. and Baroni, B.M., 2017. Isokinetic Performance of Knee Flexor and Extensor Muscles in American Football Players from Brazil. Revista Brasileira de Cineantropometria & Desempenho Humano, 19(4), pp.426-435.

Thomas, A.C., Villwock, M., Wojtys, E.M. and Palmieri-Smith, R.M., 2013. Lower extremity muscle strength after anterior cruciate ligament injury and reconstruction. Journal of athletic training, 48(5), pp.610-620.

Thorborg, K., Bandholm, T. and Hölmich, P., 2013. Hip-and knee-strength assessments using a hand-held dynamometer with external belt-fixation are inter-tester reliable. Knee Surgery, Sports Traumatology, Arthroscopy, 21(3), pp.550-555.

Toonstra, J. and Mattacola, C.G., 2013. Test-retest reliability and validity of isometric knee-flexion and-extension measurement using 3 methods of assessing muscle strength. J Sport Rehabil, (7), pp.1-5.

Undheim, M.B., Cosgrave, C., King, E., Strike, S., Marshall, B., Falvey, É. and Franklyn-Miller, A., 2015. Isokinetic muscle strength and readiness to return to sport following anterior cruciate ligament reconstruction: is there an association? A systematic review and a protocol recommendation. Br J Sports Med, 49(20), pp.1305-1310.