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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 14  |  Issue : 1  |  Page : 90-95

Validity of the IND IsoDyno isokinetic dynamometer maximum peak angular torque measure for right knee joint flexion and extension movement


1 Department of Musculoskeletal, Sancheti Institute College of Physiotherapy, Pune, Maharashtra, India
2 Department of Research, Sancheti Institute of Orthopedics and Rehabilitation, Pune, Maharashtra, India
3 Department of EnTC, College of Engineering, Savitribai Phule Pune University, Pune, Maharashtra, India
4 Petroleum Engineering, Savitribai Phule Pune University, Pune, Maharashtra, India

Date of Submission11-Mar-2020
Date of Acceptance17-Sep-2020
Date of Web Publication09-Feb-2021

Correspondence Address:
Dr. Neeraj A Athavale
Sancheti Institute College of Physiotherapy, Thube Park, Near Nexa Showroom, Shivajinagar, Pune - 411 005, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/kleuhsj.kleuhsj_63_20

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  Abstract 

Context: IND IsoDyno isokinetic dynamometer is a newly designed dynamometer to measure the isokinetic strength of the knee joint. It is a cost-effective, clinically feasible, and easily available dynamometer which manifests its benefits over the preexisting one.
Aim: The aim of this study was to assess the validity of IND IsoDyno isokinetic dynamometer with respect to maximum peak angular torque.
Settings and Design: Criterion-related validity (concurrent validity).
Materials and Methods: We considered IND IsoDyno isokinetic dynamometer as an index test and TecnoBody IsoMove isokinetic dynamometer as our reference standard. In this study, we assessed the validity of the IND IsoDyno isokinetic dynamometer and compared the obtained maximum peak angular torque values of the prototype device. Five volunteers were tested at 60° per second on concentric mode for knee flexion and extension on both the IsoMove and a new isokinetic dynamometer IND IsoDyno. Data for values of maximum peak angular torque were recorded.
Statistical Analysis Used: Interclass correlation coefficient (ICC) and standard errors of measurement (SEM) were analyzed using IBM SPSS version 26. Bland and Altman's method of analysis was done.
Results: ICC and SEM revealed a high level of reproducibility and precision in the device's maximum peak torque measurements. The 95% confidence interval (CI) interval falls between the limits of agreement on Bland and Altman's plot.
Conclusions: Within the limitations of the study, IND IsoDyno isokinetic dynamometer provided a mechanically valid measure of maximum peak angular torque on multiple trials performed on various subjects.

Keywords: Angular velocity, constant velocity, cost-effective, India, isokinetic dynamometer, maximum peak angular torque, peak torque, stepper motor, validity, variable resistance


How to cite this article:
Mahapure SS, Athavale NA, Shyam AK, Sancheti PK, Nirgude AS, Bhore NR. Validity of the IND IsoDyno isokinetic dynamometer maximum peak angular torque measure for right knee joint flexion and extension movement. Indian J Health Sci Biomed Res 2021;14:90-5

How to cite this URL:
Mahapure SS, Athavale NA, Shyam AK, Sancheti PK, Nirgude AS, Bhore NR. Validity of the IND IsoDyno isokinetic dynamometer maximum peak angular torque measure for right knee joint flexion and extension movement. Indian J Health Sci Biomed Res [serial online] 2021 [cited 2021 Feb 27];14:90-5. Available from: https://www.ijournalhs.org/text.asp?2021/14/1/90/308969




  Introduction Top


Isokinetic dynamometer provides constant velocity with accommodating resistance throughout a joint's range of motion (ROM).[1] This resistance is provided using an electric servo-controlled mechanism at a constant velocity which is defined by the user. Isokinetic muscle contraction has become a popular method by which to assess dynamic muscle function in clinical as well as in research settings. With the interfacing of isokinetic dynamometers and microprocessors, objective measures of human muscle function on variables related to torque, power, and endurance can be obtained.

Ultimately, these results are interpreted to present dynamic muscle function and are the basis of preseason screening, return to play decisions, treatment efficacy, and insurance reimbursement. However, several measurement errors such as control of lever arm velocity,[2] impact artifacts,[3] and inertial effects[4] attributable to the technological capabilities of the dynamometer can threaten the credibility of these measures.

Demonstrated validity is essential to the establishment of a credible measure of muscle function.[5] For measures of human muscle function using an isokinetic dynamometer to be reliable, they must be both consistent and error free, and for measures to be valid, they must measure the variable they are intended to measure.[6] Establishing the mechanical measuring capabilities of a dynamometer without potential error (introduced by variable human performance) provides the first step to ensure isokinetic testing is depicting clinically relevant physiological function (validity) with acceptable consistency (reliability).

The use of a mechanically reliable instrument provides assurance that each time an individual is assessed, changes which are observed in muscle function are due to the differences in performances which are actual rather than inconsistent measurement capabilities of the instrument.

Moreover, a mechanically valid instrument ensures that observations made are an assessment of a variable the clinician or investigator expected to observe.

Once mechanical validity is established, the observer is charged with the task of determining if observed changes in human performance are a direct result of applied interventions or simply an inherent inconsistency in human performance. Measures of maximum peak angular torque using a variety of isokinetic dynamometers have been found to be both mechanically reliable[7] and valid.[8]

IND IsoDyno isokinetic dynamometer is a newly designed dynamometer to measure the isokinetic strength of the knee joint. It is a cost-effective, clinically feasible, and easily available dynamometer which manifests its benefits over the preexisting one. The IND IsoDyno is a contemporary isokinetic dynamometer with an electrically controlled servomechanism which could be used in both clinical and research settings.

Therefore, the purpose of this study is to assess the mechanical validity of maximum peak angular torque measure of the IND IsoDyno isokinetic dynamometer.


  Subjects and Methods Top


Material

IND IsoDyno isokinetic dynamometer

IsoMove isokinetic dynamometer (TecnoBody)

Procedure

We have considered IsoMove isokinetic dynamometer as a reference standard and IND IsoDyno isokinetic dynamometer as an index test.

Five subjects who were recruited earlier were taken to Abhinav Bindra Targeting Performance, Pune, for trials on reference standard method. Subjects were explained the objectives of the research, and after acquiring adequate history of the subjects with respect to the right knee joint, written consent was taken to proceed with the trials. These subjects were assessed for height and body weight. Demographic data were uploaded on the software of IsoMove such as name, age, sex, address, date of birth, and contact details they were asked to perform right knee flexion and extension as fast and as strong as they could. Adjustment of the chair was done, where stabilization of the proximal joints was assured by firmly strapping the thigh and attaching firm cuff at the distal aspect of the leg. On the IsoMove software, ROM (0–90°) of the right knee was set and then isokinetic concentric mode was selected. The angular velocity was prior set at 60°/s. Initially, subjects were allowed to take trials to get accustomed to the device. As soon as the buzzer rang, subjects performed flexion and extension movement of the right knee joint as fast and as strong as they could. Five repetitions were performed, and a real-time running graph was presented on the display screen and data for values of maximum peak angular torque were recorded. These data were in the form of a printed numerical and graphical format.

A similar procedure was performed on IND IsoDyno isokinetic dynamometer, and data for values of maximum peak angular torque were recorded.

To see whether the prototype device is measuring maximum peak angular torque with minimal error, both devices (reference and prototype) recorded values of maximum peak angular torque for comparison. The trails on reference standard devices were considered as method 1 and trails on the prototype device were considered method 2.

For comparing measures of diagnostic accuracy, interclass correlation coefficient and standard error of the mean (SEM) of values of maximum peak angular torque for flexion and extension movements with both the methods were derived using SPSS version 26 (IBM Corp., Armonk, New york, USA).

To analyze the variability in the diagnostic accuracy, Bland and Altman's analysis was done distinguishing the reference standard from index testing. Ethical Clearance was obtained from Institutional Ethics Committee Sancheti Institute of Orthopaedic and Rehabilitation with Ref no IEC No: IEC-SIOR / Agenda 057 dated: 6th August 2019.


  Results Top


  • Bland and Altman's plot shows that there is an agreement between two quantitative methods of measurements (evaluation)
  • r = 0.996 (-1 ≤ r ≤ 1.0) which implies that the correlation coefficient is a perfect positive correlation and the correlation measurement is error free
  • R2: 0.992 (0 = R2 = 1) which implies that the dependent variable is 99% predictable
  • Smallest detectable change is < 10 Nm, an error which was considered a priori
  • Smallest detectable change is less than minimal important change
  • Upper and lower limits on BandA plot (line of agreement [LOA]) are 10.52 and 2.68, respectively, for flexion movement
  • Upper and lower limits on BandA plot (LOA) are 10.5 and 2.3, respectively, for extension movement
  • The 95% CI interval falls between the limits of agreement on Bland and Altman's plot
  • Standard error of measurement (SEMf) = 14.3 and SEMe = 17.3 for flexion and extension movement, respectively
  • The strong interclass correlation coefficients (ICCs) and small SEMs support the new device's validity in the measurement of isokinetic torque
  • Please refer [Table 1] and [Table 2] and [Figure 1],[Figure 2],[Figure 3],[Figure 4] for detailed information.
Table 1: Flexion of right knee joint

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Table 2: Extension of right knee joint

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Figure 1: Photograph of the newly devised isokinetic dynamometer named as IND IsoDyno

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Figure 2: Graph for flexion of right knee joint

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Figure 3: Graph for flexion of right knee joint

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Figure 4: Graph for extension of right knee joint

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  Discussion Top


Baltzopoulos V in 1989 stated that isokinetic contraction is the muscular contraction that accompanies constant velocity limb movements around a joint. The velocity of movement is maintained by a special dynamometer. The resistance of the dynamometer is equal to the muscular forces applied throughout the range of movement. This method allows the measurement of the muscular forces in dynamic conditions and provides optimal loading of muscles. However, during movements in the vertical plane, the torque resisted by the dynamometer is the resultant torque produced by the muscular and gravitational forces.

The error depends on the angular position and the torque potential of the tested muscle group. Several methods have been developed for the correction of gravitational errors in isokinetic data. The torque output also contains artifacts that are associated with the inertial forces during acceleration and deceleration periods for the development of the constant preset angular velocity. For an accurate assessment of a muscle function, only constant velocity data should be analyzed. The most frequently used isokinetic parameters are the maximum torque and the angular position where it is recorded, the toque output at different angular velocities of movement, the torque ratio of the reciprocal muscle groups, and the torque output during repeated contractions. The unique features of isokinetic dynamometry are optimal loading of the muscles in dynamic conditions and constant preselected velocity of the movement. These features provide safety in the rehabilitation of patients with muscular and ligament injuries. Isokinetic dynamometry has also been used for the training of various muscle groups in order to improve the muscular performance in dynamic conditions. The movement velocity of the different activities can be simulated during training in order to improve the training effect. Data acquisition and analysis have been improved using a computer system interfaced to isokinetic dynamometers.

Recently developed computer system provides correction for gravitational and inertial errors, accurate computation of isokinetic parameters, and real-time display of the torque output.

Fontana MF et al. in 2002 stated that participation in intensive sports activities leads to muscular specialization that may generate alteration in involved articular forces and cause static (posture) and dynamic changes (alterations of articular stability, coordination, etc.). Prevention of injury requires specific functional muscular evaluation in all athletes and for any kind of sport.

Jones PA et al. in 2010 stated that muscle strength imbalances have been linked with poor agility performance and higher injury risk. Isokinetic dynamometry has been used to investigate such imbalances; however, this method is impractical and inaccessible for the most strength and conditioning coaches. The aim of the study was to compare isokinetic dynamometry with functional field tests for assessing bilateral strength imbalance. The findings provide support for the use of field tests to detect imbalances between lower limbs, but the ultimate choice of test used should depend on the specific strength quality that predominates in the sport.

Newton RU et al. in 2006 determined whether a significant strength imbalance existed between the left and right or dominant (D) and nondominant (ND) legs and (B) to investigate possible correlation among various unilateral and bilateral closed kinetic chain tests, including a field test and traditional isokinetic dynamometry used to determine strength imbalances. The results of this study indicate that a significant strength imbalance can exist in collegiate level athletes.

Drouin JM et al. in 2004 quantitatively assessed the mechanical reliability and validity of the position torque and velocity measurements of the Biodex System 3 isokinetic dynamometer.[9] Trail-to-trial and day-to-day reliability was assessed during three trials on 3 separate days. To assess instrument validity, the measurement of each variable using Biodex System 3 dynamometer was compared to a criterion measure of position, torque, and velocity. The position was assessed at 5° of increment across the available ROM of the dynamometer. Torque measures were assessed isometrically by hanging six different calibrated from the lever arm. Velocity was assessed across 70° of arc of motion by manually accelerating the weighted lever arm. With the exception of a systematic decrease in velocity at speeds of 300 degrees/s and higher, the Biodex System 3 performed with acceptable mechanical reliability and validity on all variables tested.

Orri JC in 2008 assessed the mechanical reliability and validity of the INRTEK iSAM 9000 isokinetic dynamometer[10] and compared the obtained torque values of the prototype device with those from a traditional device.

With the consideration of the above studies, we have developed the IND IsoDyno isokinetic dynamometer which is cost-effective, clinically feasible, and easily available in the market. It provides constant velocity with accommodating resistance throughout a joint's ROM. This resistance is provided using an electrical servo-controlled mechanism at a user-defined constant velocity. With the interfacing of isokinetic dynamometers and microprocessors, objective measures of human muscle function on variable related to maximum peak angular torque can be obtained.

Demonstrated validity is essential to the establishment of a credible measure of muscle function. For measures of human muscle function using an isokinetic dynamometer to be reliable, they must be both consistent and error free, and for measures to be valid, they must measure the variable they are intended to measure. Establishing the mechanical measuring capabilities of a dynamometer without potential error (introduced by variable human performance) provides the first step to ensure isokinetic testing is depicting clinically relevant physiological function (validity) with acceptable consistency (reliability).

The use of a mechanically valid instrument provides assurance that each time an individual is assessed, observed changes in muscle function are due to differences in the actual performances rather than inconsistent measurement capabilities of the instrument.

In order to determine if observed changes in human performance are a direct result of applied interventions or simply an inherent inconsistency in human performance, the validity of IND IsoDyno isokinetic dynamometer was established.

However, TecnoBody IsoMove isokinetic dynamometer was considered as a reference standard for this study. Criterion-related validity measurement was determined by deriving SEM and correlation coefficient between the values of maximum peak angular torque by method 1 and method 2 for flexion and extension movement, and a statistical agreement was done by Bland and Altman's[11],[12],[13],[14],[15],[16],[17],[18],[19],[20],[21],[22],[23],[24],[25],[26],[27],[28],[29] analysis method.

Correlation coefficient is r = 0.996; normative value ranges - 1 ≤ r ≤ 1.0, which implies that the correlation coefficient is a positive correlation and the correlation measurement is error free.

SEMf = 14.3 and SEMe = 17.3 for flexion and extension movement, respectively.

The strong ICCs and small SEMs support the new device's validity in the measurement of isokinetic torque.

IND IsoDyno isokinetic dynamometer could be used for assessing isokinetic concentric strength of the right knee joint since the validity of maximum peak torque is acceptable for both clinical and research purposes.

Limitations

Encoder is not placed for measuring the speed and is compensated by the optical proximity sensors based on infrared radiations.

Servo lock is not reversed since the motor would generate its own energy and damage the Arduino circuit.

Mechanical interlock should be lodged to refine the next generation of IND IsoDyno isokinetic dynamometer.

We would be fostering testing of multiple joints with the help of a similar electro-mechanical system which is not present currently.


  Conclusions Top


Within the limitations of the study, IND IsoDyno isokinetic dynamometer provided a mechanically valid measure of maximum peak angular torque on multiple trials performed on various subjects.

Clinical implication

IND IsoDyno isokinetic dynamometer could be used for assessing isokinetic concentric strength of the knee joint since the validity of maximum peak torque is acceptable for clinical as well as research purposes.

Further scope of the study

Further studies must incorporate reliability and validity on more number of samples and develop eccentric and isometric mode to IND IsoDyno and testing for multiple joints. The findings of this study will be used to refine the next generation of the IND IsoDyno with respect to test protocols and the reliability of measuring human muscle performance.

Financial support and sponsorship

This study was financially supported by Maharashtra University of Health Sciences, Nashik, Avishkar fellowship.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2]



 

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