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Research Quarterly for Exercise and Sport Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/urqe20
Reliability of Muscle Mechanical Characteristics for Isokinetic and Isotonic Squat and Bench Press Exercise Using a Multifunction Computerized Dynamometer a
Tibor HortobáGyi & Frank I. Katch
b
a
Department of Sport Science/Biology 2000 S. Gaylord , University of Denver , Denver , CO , 80210 , USA b
Department of Exercise Science , University of Massachusetts , Amherst , MA , 01003 , USA Published online: 26 Feb 2013.
To cite this article: Tibor HortobáGyi & Frank I. Katch (1990) Reliability of Muscle Mechanical Characteristics for Isokinetic and Isotonic Squat and Bench Press Exercise Using a Multifunction Computerized Dynamometer, Research Quarterly for Exercise and Sport, 61:2, 191-195, DOI: 10.1080/02701367.1990.10608674 To link to this article: http://dx.doi.org/10.1080/02701367.1990.10608674
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
HORTOBAOYI AND KATCH
RBSIlARCH
RBSBARCH QuARTBRLY
Nom
FOR ExBRCISB AND SPORT
1990,VOL. 61, No.2, pp. 191-195
Reliability of Muscle Mechanical Characteristics for Isokinetic and Isotonic Squat and Bench Press Exercise Using a Multifunction Computerized Dynamometer TIBOR RORTOBAGYI University of Denver
Downloaded by [University of Otago] at 08:18 06 January 2015
FRANK I. KATeR University of Massachusetts
Method
Keywords: muscle,reliability,dynamometry, strengthtesting
Torque andforcearetypicalcriterionmeasuresoftenusedto evaluate"muscular strength"usingcomputerizeddata acquisition. Reliability of the torque and force scores are usually highandexceedr= .90 (Agreetal., 1987;Farrel & Richards, 1986;Jacobs & Pope, 1986;Johnson & Siegel, 1978;Knapik, Wright, Mawdsley, & Brawn, 1983; Moffroid, Whipple, Hofkosh,Lowman, & Thistle, 1969).However,with computerizeddevices,additionalusefulinformationcanbe obtained such as angle of peak torque in the range of motion, work or powerforeachrepetitionofexercise,velocity,timeintervalto peak torque, and rate of torque development Such measures may provide a better descriptionof skeletal muscleperformance than torque or force alone. However, previous studies have not evaluatedthe reliabilityfor such softwaregenerated scores. The prior studies have assessed reliability for measures of torque using simple arm (Kroll, 1970; Nelson & Fahrney,1965;Ostemig,Bates, & James, 1977)or leg movements (Burdett & Van Swearingen, 1987; Thistle, Hislop, Moffroid, & Lowman, 1967)that are dissimilarto the skilled movements often prevalent in gross motor tasks. The new generationof computer-interfaced devicespermits an evaluation of muscular strength for exercises that includethe wholebody motionsof theuprightsquator supine benchpress.Inthepresentstudy,weassessedthereliabilityof musclemechanicalcharacteristics(peakforce, velocity,time to peak force, time to peak velocity, rise time, power, and work output) during either isokineticand isotonic squat and bench press exercise using a multifunction, computerized dynamometer.
Subjects The subjectswere24 male studentsand staff members at the University.Their mean age was 27.1 years (SD =±S.IS), stature was 177.4 em (±6.68), and body mass was 76.1 kg (±10.11). Informed written consent was obtained prior to participation.
Testing equipment Upright squat (SQ) and supine bench press (BP) exercises wereperformedon a hydraulic,multifunction exerciser (Ariel Dynamics Inc., Trabuco Canyon, CA). With this device, fluid is forced through an adjustable valve opening in response to the movementof an exercise bar. The valve size is controlled with a fast-response stepper motor. The dynamometerincludesa potentiometerand force transducer with an analog-to-digital interfaceto a microcomputer for on-line dataacquisitionata samplingrateof 16,000Hz.Thereare two choices for exercise mode; the isokinetic mode requires the selection of a preset angular velocity with torque as the criterionoutput.The isotonic mode is set by usinga constant resistance(load),and the maximummovementvelocity is the criterion score attained at the preset load. Differentexercise modesand routines can be preprogrammed, and the acquired data are stored on floppy disks for future report generation. The testing apparatus was calibrated before each test sessionbyhanging40- to l00-kg weightson thehandlesofthe exercise bar. Jacobs and Pope (1986) have previously reportedadditionaltechnicaldetailsand validationinformation about the Ariel multifunction dynamometer.
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Testing
Results
Subjects were tested twice on different days with a twoto four-dayinterval between tests, and testing was conducted at the same time of day on both test days. Standardized instructions were provided, and a warm-up prior to testing included 10 full squats (no resistance) and 10 push-ups; this was followed by 5 squatting and bench press movements withoutresistance using the exercise bar of the dynamometer. To assess the reliability of repetition work, range of motion was set so subjects moved the exercise bar the same absolute distance during the squat (-100°) and bench press (-600). A balanced experimental design was employed across subjects,exercises,and days. Subjects were testedfor 3 sets of 3 reps of isokinetic SQ, 3 sets of2 reps of isokineticBP, 3 sets of 4 reps of isotonic SQ, and 3 sets of 4 reps of isotonic BP. There was a 2- to 3-s pause between trials, and a l-min rest between sets. For isokinetic exercise, the testing speed was 5°·s-1 (0.087 rad-s"), For isotonic BP, a preset resistance equivalent to 196.2 N (20 kg) external load had to be overcome at maximal speed. During isotonicSQ, the externalload was 686.7 N (70 kg). These particular loads, number of reps, and speeds of movement were chosen after considerable trial and error in pilot studies using trained and untrainedsubjects. For the isokinetic mode, the criterion measures were maximal isokineticrepetition force, peak and average power, repetition work, time to peak force, and rise time. For the isotonic mode, the criterion scores included repetition peak velocity, peak and average power, time to peak velocity, and rise time. Time to peak was the time interval to attain peak force(or velocity)from the first movementof theexercise bar. Rise time was the rate of force (or velocity)development that represented the 10% to 90% portion of the force or velocitytime curve. For the isokinetic mode, repetition force and work were recorded for each trial, and velocity was measured for every repetition during isotonic exercise. For the other criterion scores, only the means for each set were available from the computer-generated scores. While the analysis of isokinetic SQ included3 setsof 3 trialson Days 1and 2 (9 scoreson each day), the corresponding analysis for peak power included the meanof each of3 sets on Days 1 and 2 (3 scores on each day).
Statistical procedures A paired, two-tailedr-testwas usedto compare the means on Days 1and 2. For thecriterion scores securedover multiple trials and days, the trials, days, and interaction effects were assessedby a two-way nested, random model,repeated measures analysis of variance. Trials were nested within days, and days were nested within subjects (Feldt & McKee, 1958; Haggard,1958;Safrit, Atwater,Baumgartner, & West, 1976). The intraclass reliability correlation (R) was computed from the appropriate sums of squares.
Table 1 presents descriptive data for isokinetic and isotonic SQand BP. The between-daypercent differencesfor the 6 criterion measures of isokinetic SQ and BP ranged from -10.8% (rise time, SQ) to 5.4% (time to peak force, SQ). The correspondingvalues for the 5 criterion measures of isotonic SQ and BP were -3.5%(time to peak velocity,SQ) and 10.6% (peakpower, BP). Surprisingly, there was essentiallyno dayto-day variationexpressed as a percentage of the Day 1 and 2 scores for isokinetic BP peak power, average power, time to peak, and rise time. The results of the paired t-tests revealed significant day-to-day differences for 3 of the 5 isotonic BP criterion measures, but not for isotonic SQ. The results of the 2-way repeated measures analysis of variance revealed a significant trials effect for isokinetic SQ (see Figure IA) and BP (see Figure 1C), a significantdays by trials interaction for isotonic SQ (see Figure IB), and a significantdays effect for isotonic BP (see Figure ID). Table 2 presents the Rs for the mechanical characteristics of isokinetic and isotonic exercise. The trials effects were significant (p < .05)for 5 variables,3 weresignificantfor days,and2 were significantfor the interaction.In 8 cases, the Rs werelowerfor average and peak power, time to peak force, and time to peak velocity than the Rs for peak force and velocity (see Table 2 and Figure 1).
Discussion Reliabilityestimatesinpriorstudieson muscularstrength havebeen restricted to a limited numberof criterion measures suchasisometric(Kroll,I964,1970)ordynamicforce(Burdett & Van Swearingen, 1987; Farrel & Richards, 1986). In the present study, the 24 subjects were tested on 2 days for 11 criterion measures with a computerized dynamometer. The largestday-to-daydifferencesoccurred for rise time (-10.8%, isokinetic SQ) and peak power (10.6%, isotonic BP). When these two extremes were not included in the calculations, the average day-to-day variation was reduced to -2%. This is similar to findings reported by Jacobs and Pope (1986), who used a similar dynamometer but different exercises, and to reports that usedother computerizeddynamometers(Johnson & Siegel, 1978;Knapik & Ramos, 1980).It shouldbe emphasized that the day-to-day variability of the criterion measures in the current study were obtained for multijoint movements (standing SQ and supine BP), whereas previous determinationsof reliabilitywere mostlyfor simpleelbowflexion(Agre et al., 1987; Nelson & Fahrney, 1965) or knee extension (Knapik et al., 1983; Moffroid et al., 1969). In prior studies, reliability was not established for mechanical characteristics of skeletal muscle such as work, power, time to peak force, time to peak velocity,and rise time
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Table 1 Mean, Standard Deviation (In parentheses), and % Differences (%~) for Day 1 and Day 2 Criterion Scores for lsoklnetlc and Isotonic Squat and Bench Press Exercise
Criterion Score Isokinetic Peak force, N Peak work, J Peak power, d-s: Average power, J's" Time to peak force, ms
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Rise time, ms
Isotonic Peak velocity, Had-s: Peak power, d-s: Average power, J's" Time to peak velocity, ms Rise time, ms
Day 1
Squat Day 2
2074.1 (557.10) 400.3 (173.61) 365.2 (119.08) 269.3 (90.08) 1328.5 (257.71) 773.1 (251.61)
2126.3 (560.03) 398.6 (165.72) 375.8 (156.76) 276.7 (115.18) 1399.7 (642.88) 689.4 (218.52)
0.92 (0.206) 1119.2 (423.36) 760.7 (246.22) 469.4 (73.77) 496.5 (94.66)
0.95 (0.202) 1104.6 (343.64) 759.4 (232.13) 453.2 (111.46) 485.1 (101.22)
%~
Day1
Bench Press Day 2
2.5
1031.8 (329.07) 255.2 (95.11) 178.3 (68.55) 139.7 (55.43) 1725.4 (391.87) 1331.2 (409.76)
1042.7 (332.11) 261.3 (102.29) 178.2 (64.57) 139.6 (49.09) 1722.4 (435.17) 1330.9 (432.91)
0.91 (0.145) 479.6 (168.71) 309.7 (107.85) 735.1 (258.61) 508.3 (111.47)
0.95 (0.137) 530.5 (193.56) 331.3 (120.07) 711.9 (255.99) 516.5 (114.59)
-0.4 2.9 2.7 5.4 -10.8*
3.3 -1.3 -0.2 -3.5 -2.3
%~
1.1 2.4 0.0 0.0 0.2 0.0
4.4* 10.6* 7.0* -3.2 1.6
*Significant difference between the means for Days 1 and 2; paired t-test (p .OS,one-way ANOVAwithrepeatedmeasures). For isokineticBP (seeFigure I C), therewasalsoa significant
trials effect across days without a days effect. Although the trialseffectdid notoffsetthe reliability of this measure, it did indicate the possibility of a "measurementschedule effect" (Kroll, 1970). An alternativethat would improve the current protocol would be to allow for longer rest periods between trialsandsetsor to useonlyonesetof onetrialwithlongerrest intervals between sets. We believe that the decrement in performance for isokinetic BP (see Figure 1C) wasrelatedto the smallermusclemassof the upperextremities in comparisonto SQexercisewhereperformance wasmorestableacross sets (seeFigure lA). Concerning the days x trialsinteraction for isotonicSQ (see Figure lB), removalof the unstable first trial on both days eliminated the significant interaction (F= 1.67;p> .05,two-way ANOVAwithrepeatedmeasures). Figure ID demonstrates that there wasa smallbut significant dayseffectforisotonicBPexercise.Wehavenologicalexplanationwhythisoccurred. The scoresonDay2 werehigherby an averageof 3.5% (P< .05),but an ordereffectwas unlikely because testing sequence was balanced across exercises, subjects, and test days. While muscular performance may increaseunderrepeatedtestconditionsduetolearning (Henry, 1942; Schenck & Forward, 1965) or reminiscence (Sage, 1984), such factors cannot explain why subjectsperformed
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Table 2 Intraclass Correlations for the Mechanical Characteristics of lsoklnetlc and Isotonic Squat and Bench Press Exercise Isokinetic Squat Bench 0.928· 0.890 0.893 0.695 0.816 t
Repetition work Peak power Average power Time to peak Rise time
0.817· 0.911 0.951 0.910 0.919·
better on the second testing day for only 1 of the 4 exercise modes. For isotonic BP, at least 8 prior trials over 2 days were apparently needed before stabilization occurred. Indeed, there was no significant days effect for the last set of exercise over the 2 test days (F = 1.11; p > .05; one-way ANOYA with repeated measures). In summary, a computerizeddynamometer has been used to assess reliability of multijoint upper and lower body muscular performance for 11 criterion measures. Day-to-day variabilityforallmeasuresrangedbetween-1O.8%andlO.6%; there was also stability in the reliability coefficients for multiple scores across days. In addition to the conventional measures of peak force and velocity, reliability was also evaluated for other muscle mechanical characteristics, which included time to peak force, time to peak velocity, rise time. power, and work output. Reliability exceeded R =.85 in 6 of the 11 computer generated scores. Thus, we conclude that
Isotonic Squat Bench _II 0.936· 0.880 0.878' 0.920
0.970t 0.971 ot' 0.774 0.794
Downloaded by [University of Otago] at 08:18 06 January 2015
IINot measured ·Significant Trials effect (p < .05). tSignificant Days effect (p < .05). 'Significant Days x Trials interaction (p < .05).
A. Isokinetic Squat 200
Set 1
Set 2
190 :.
...=
-"
180
~
;Z
-s
170
:.J l.
B. Isotonic Squat
~ ~
150
012
3
~ ~
~
....
0.8
.~
I:
456
e ;;>-
Set 1
y
789
0.7
2
0
Repetitions
c.
...=
100
~
Z
er
90
~
4
/:
6
8
Day 1 Day 2
10
12
D. Isotonic Bench Press
Set 2
Set 3
:::::: -,
~ ....
1.0
Set 1
0.9
~
~
l.
....~
0.8
Set 2
--
Set 3
• •
~
~
.~
:.J l. Q
~
Set 1
~
Repetitions
Isokinetic Bench Press
110
Set3
R = 0.969 Days: F = 0.02 Trials: F = 1.86 D X T: F = 2.01*
~
Day 1 Day 2
Set 2
0.9
....
l.
R = 0.978 Days: F = 0.01 Trials: F = 4.10* DX T: F= 1.11
e 160
~
1.0
Set 3
80
o
R = 0.861 Days: F = 0.74 Trials: F = 8.73* D X T: F = 1.36 1
-0-
---
234
e ;;>~
Day 1 Day 2
5
0.7
0
6
R = 0.959 Days: F = 5.07* Trials: F = 1.66 D X T: F = 1.10 2
4
-0-
--6
8
Day 1 Day 2
10
I 12
Repetitions
Repetitions
Figure 1. Mean values for 24 males tested on two days for lsoklnetlc squat (A), Isotonic squat (B), Isoklnetlc bench press (C), and Isotonic bench press (D). The Insert Includes the Intraclass R, and the Fratlos for days, trials, and Interaction. ·slgnlflcant effect (p < .05). RBsIlAllCH QuARTIlRLY POR ExERCISB AND SPORT, VOL.
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muscle mechanical characteristics for the squat and bench press can be reliably assessed with the multifunction dynamometer.
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References Agre, J. C., Magness, J. L., Hull, S. Z., Wright, K. C., Baxter, T. L., Patterson, R., & Stradel, L. (1987). Strength testing with a portable dynamometer: Reliability for upper and lower extremities. Archives ofPhysical Medicine andRehabilitation, 68, 454-458. Burdett, R. G., & Van Swearingen, 1.(1987). Reliability ofisokinetic muscle endurance tests. JourTI/JI of Orthopaedic and Sports Physical Therapy, 8, 484-488. Farrel, M., & Richards, J. G. (1986). Analysis of the reliability and validity of the kinetic communicator exercise device. Medicine and Science in Sports and Exercise, 18, 44-49. Feldt, L. S., & McKee, M. E. (1958). Estimation of reliability of skill tests. Research Quarterly, 29, 279-293. Haggard, E. A. (1958). Intraclass correlation and the analysis of variance. New York: Dryden. Henry, F. (1942). The practice and fatigue effects in the Sargent test. Research Quarterly,l3, 16-29. Jacobs, I., & Pope, 1. (1986). A computerized system for muscle strengthevaluation: Measurementreproducibility, validity, and some normative data. National Strength and Conditioning Association Journal, 8, 28-33. Johnson, J., & Siegel, D. (1978). Reliability of an isokinetic movement of the knee extensors. Research Quarterly, 49, 88-92. Knapik, 1.1., & Ramos, M. U. (1980). Isokinetic and isometric torque relationships in the human body. Archives ofPhysical Medicine and Rehabilitation, 61, 64-67. Knapik, J. J., Wright, J. E., Mawdsley, R. H., & Brawn, J. (1983). Isometric, isotonic, and isokinetic torque variations in four musclegroups through a range ofmotion. PhysicalTherapy, 63, 938-947. Kroll, W. (1964). Reliability variations of strength in test-retest situations. Research Quarterly, 34, 50-56.
REsEAROi
QuAR11lRLY FOIl
Kroll, W. (1970). Test reliability and errors of measurement at several levels of absolute isometric strength. Research Quarterly,41,155-162. Moffroid, M., Whipple, R., Hofkosh, 1., Lowman, E., & Thistle, H. (1969). A study of isokinetic exercise. Physical Therapy, 49, 735-746. Nelson, R. C., & Fahrney, R. A. (1965). Relationship between strength and speed of elbow flexion. Research Quarterly, 36, 455-463. Osternig, L. R., Bates, B. T., & James, S. L. (1977). Isokinetic and isometric torque force relationships. Archives of Physical Medicine and Rehabilitation, 58, 254-257. Safrit, M. 1., Atwater, A. E., Baumgartner, T. A., & West, C. (1976). Reliability Theory. Washington, DC: American Alliance for Health, Physical Education, and Recreation. Sage, G. H. (1984). Motor learning and control. Dubuque, IA: W.C. Brown Publishers. Schenck, J. M., & Forward, E. M. (1965). Quantitative strength changes with test repetitions. Physical Therapy, 45,562-569. Thistle, H. G., Hislop, H. 1.,Moffroid,M., & Lowman, E. W. (1967). Isokinetic contraction: A new concept of resistive exercise. ArchivesofPhysicalMedicine and Rehabilitation, 48,279-282.
Authors' Note This research was supported in part by a grant from HydraFitness Industries, Belton, TX. Appreciation is extended to P. F. LaChance for his expertise with data collection.
Submitted: August 19,1988 Accepted: April 16, 1989 Tibor Hortobagyi is an adjunctprofessorin theDepartment of Sport Science/Biology, 2000 S. Gaylord, University of Denver,Denver,CO80210.Frankl. Katchis aprofessor and the chairman oftheDepartment ofExercise Science, University ofMassachusetts, Amherst, MA 01003.
ExERasB
195
AND SPOR.T, VOL.
61, No.2
Research Quarterly for Exercise and Sport Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/urqe20
Reliability of Muscle Mechanical Characteristics for Isokinetic and Isotonic Squat and Bench Press Exercise Using a Multifunction Computerized Dynamometer a
Tibor HortobáGyi & Frank I. Katch
b
a
Department of Sport Science/Biology 2000 S. Gaylord , University of Denver , Denver , CO , 80210 , USA b
Department of Exercise Science , University of Massachusetts , Amherst , MA , 01003 , USA Published online: 26 Feb 2013.
To cite this article: Tibor HortobáGyi & Frank I. Katch (1990) Reliability of Muscle Mechanical Characteristics for Isokinetic and Isotonic Squat and Bench Press Exercise Using a Multifunction Computerized Dynamometer, Research Quarterly for Exercise and Sport, 61:2, 191-195, DOI: 10.1080/02701367.1990.10608674 To link to this article: http://dx.doi.org/10.1080/02701367.1990.10608674
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
HORTOBAOYI AND KATCH
RBSIlARCH
RBSBARCH QuARTBRLY
Nom
FOR ExBRCISB AND SPORT
1990,VOL. 61, No.2, pp. 191-195
Reliability of Muscle Mechanical Characteristics for Isokinetic and Isotonic Squat and Bench Press Exercise Using a Multifunction Computerized Dynamometer TIBOR RORTOBAGYI University of Denver
Downloaded by [University of Otago] at 08:18 06 January 2015
FRANK I. KATeR University of Massachusetts
Method
Keywords: muscle,reliability,dynamometry, strengthtesting
Torque andforcearetypicalcriterionmeasuresoftenusedto evaluate"muscular strength"usingcomputerizeddata acquisition. Reliability of the torque and force scores are usually highandexceedr= .90 (Agreetal., 1987;Farrel & Richards, 1986;Jacobs & Pope, 1986;Johnson & Siegel, 1978;Knapik, Wright, Mawdsley, & Brawn, 1983; Moffroid, Whipple, Hofkosh,Lowman, & Thistle, 1969).However,with computerizeddevices,additionalusefulinformationcanbe obtained such as angle of peak torque in the range of motion, work or powerforeachrepetitionofexercise,velocity,timeintervalto peak torque, and rate of torque development Such measures may provide a better descriptionof skeletal muscleperformance than torque or force alone. However, previous studies have not evaluatedthe reliabilityfor such softwaregenerated scores. The prior studies have assessed reliability for measures of torque using simple arm (Kroll, 1970; Nelson & Fahrney,1965;Ostemig,Bates, & James, 1977)or leg movements (Burdett & Van Swearingen, 1987; Thistle, Hislop, Moffroid, & Lowman, 1967)that are dissimilarto the skilled movements often prevalent in gross motor tasks. The new generationof computer-interfaced devicespermits an evaluation of muscular strength for exercises that includethe wholebody motionsof theuprightsquator supine benchpress.Inthepresentstudy,weassessedthereliabilityof musclemechanicalcharacteristics(peakforce, velocity,time to peak force, time to peak velocity, rise time, power, and work output) during either isokineticand isotonic squat and bench press exercise using a multifunction, computerized dynamometer.
Subjects The subjectswere24 male studentsand staff members at the University.Their mean age was 27.1 years (SD =±S.IS), stature was 177.4 em (±6.68), and body mass was 76.1 kg (±10.11). Informed written consent was obtained prior to participation.
Testing equipment Upright squat (SQ) and supine bench press (BP) exercises wereperformedon a hydraulic,multifunction exerciser (Ariel Dynamics Inc., Trabuco Canyon, CA). With this device, fluid is forced through an adjustable valve opening in response to the movementof an exercise bar. The valve size is controlled with a fast-response stepper motor. The dynamometerincludesa potentiometerand force transducer with an analog-to-digital interfaceto a microcomputer for on-line dataacquisitionata samplingrateof 16,000Hz.Thereare two choices for exercise mode; the isokinetic mode requires the selection of a preset angular velocity with torque as the criterionoutput.The isotonic mode is set by usinga constant resistance(load),and the maximummovementvelocity is the criterion score attained at the preset load. Differentexercise modesand routines can be preprogrammed, and the acquired data are stored on floppy disks for future report generation. The testing apparatus was calibrated before each test sessionbyhanging40- to l00-kg weightson thehandlesofthe exercise bar. Jacobs and Pope (1986) have previously reportedadditionaltechnicaldetailsand validationinformation about the Ariel multifunction dynamometer.
R!lSBAR0l QuAR11lRLY FOR ExBRCISIl AND SPORT, VOL.
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61, No.2
HORTOBAoYI AND KATeH
Downloaded by [University of Otago] at 08:18 06 January 2015
Testing
Results
Subjects were tested twice on different days with a twoto four-dayinterval between tests, and testing was conducted at the same time of day on both test days. Standardized instructions were provided, and a warm-up prior to testing included 10 full squats (no resistance) and 10 push-ups; this was followed by 5 squatting and bench press movements withoutresistance using the exercise bar of the dynamometer. To assess the reliability of repetition work, range of motion was set so subjects moved the exercise bar the same absolute distance during the squat (-100°) and bench press (-600). A balanced experimental design was employed across subjects,exercises,and days. Subjects were testedfor 3 sets of 3 reps of isokinetic SQ, 3 sets of2 reps of isokineticBP, 3 sets of 4 reps of isotonic SQ, and 3 sets of 4 reps of isotonic BP. There was a 2- to 3-s pause between trials, and a l-min rest between sets. For isokinetic exercise, the testing speed was 5°·s-1 (0.087 rad-s"), For isotonic BP, a preset resistance equivalent to 196.2 N (20 kg) external load had to be overcome at maximal speed. During isotonicSQ, the externalload was 686.7 N (70 kg). These particular loads, number of reps, and speeds of movement were chosen after considerable trial and error in pilot studies using trained and untrainedsubjects. For the isokinetic mode, the criterion measures were maximal isokineticrepetition force, peak and average power, repetition work, time to peak force, and rise time. For the isotonic mode, the criterion scores included repetition peak velocity, peak and average power, time to peak velocity, and rise time. Time to peak was the time interval to attain peak force(or velocity)from the first movementof theexercise bar. Rise time was the rate of force (or velocity)development that represented the 10% to 90% portion of the force or velocitytime curve. For the isokinetic mode, repetition force and work were recorded for each trial, and velocity was measured for every repetition during isotonic exercise. For the other criterion scores, only the means for each set were available from the computer-generated scores. While the analysis of isokinetic SQ included3 setsof 3 trialson Days 1and 2 (9 scoreson each day), the corresponding analysis for peak power included the meanof each of3 sets on Days 1 and 2 (3 scores on each day).
Statistical procedures A paired, two-tailedr-testwas usedto compare the means on Days 1and 2. For thecriterion scores securedover multiple trials and days, the trials, days, and interaction effects were assessedby a two-way nested, random model,repeated measures analysis of variance. Trials were nested within days, and days were nested within subjects (Feldt & McKee, 1958; Haggard,1958;Safrit, Atwater,Baumgartner, & West, 1976). The intraclass reliability correlation (R) was computed from the appropriate sums of squares.
Table 1 presents descriptive data for isokinetic and isotonic SQand BP. The between-daypercent differencesfor the 6 criterion measures of isokinetic SQ and BP ranged from -10.8% (rise time, SQ) to 5.4% (time to peak force, SQ). The correspondingvalues for the 5 criterion measures of isotonic SQ and BP were -3.5%(time to peak velocity,SQ) and 10.6% (peakpower, BP). Surprisingly, there was essentiallyno dayto-day variationexpressed as a percentage of the Day 1 and 2 scores for isokinetic BP peak power, average power, time to peak, and rise time. The results of the paired t-tests revealed significant day-to-day differences for 3 of the 5 isotonic BP criterion measures, but not for isotonic SQ. The results of the 2-way repeated measures analysis of variance revealed a significant trials effect for isokinetic SQ (see Figure IA) and BP (see Figure 1C), a significantdays by trials interaction for isotonic SQ (see Figure IB), and a significantdays effect for isotonic BP (see Figure ID). Table 2 presents the Rs for the mechanical characteristics of isokinetic and isotonic exercise. The trials effects were significant (p < .05)for 5 variables,3 weresignificantfor days,and2 were significantfor the interaction.In 8 cases, the Rs werelowerfor average and peak power, time to peak force, and time to peak velocity than the Rs for peak force and velocity (see Table 2 and Figure 1).
Discussion Reliabilityestimatesinpriorstudieson muscularstrength havebeen restricted to a limited numberof criterion measures suchasisometric(Kroll,I964,1970)ordynamicforce(Burdett & Van Swearingen, 1987; Farrel & Richards, 1986). In the present study, the 24 subjects were tested on 2 days for 11 criterion measures with a computerized dynamometer. The largestday-to-daydifferencesoccurred for rise time (-10.8%, isokinetic SQ) and peak power (10.6%, isotonic BP). When these two extremes were not included in the calculations, the average day-to-day variation was reduced to -2%. This is similar to findings reported by Jacobs and Pope (1986), who used a similar dynamometer but different exercises, and to reports that usedother computerizeddynamometers(Johnson & Siegel, 1978;Knapik & Ramos, 1980).It shouldbe emphasized that the day-to-day variability of the criterion measures in the current study were obtained for multijoint movements (standing SQ and supine BP), whereas previous determinationsof reliabilitywere mostlyfor simpleelbowflexion(Agre et al., 1987; Nelson & Fahrney, 1965) or knee extension (Knapik et al., 1983; Moffroid et al., 1969). In prior studies, reliability was not established for mechanical characteristics of skeletal muscle such as work, power, time to peak force, time to peak velocity,and rise time
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Table 1 Mean, Standard Deviation (In parentheses), and % Differences (%~) for Day 1 and Day 2 Criterion Scores for lsoklnetlc and Isotonic Squat and Bench Press Exercise
Criterion Score Isokinetic Peak force, N Peak work, J Peak power, d-s: Average power, J's" Time to peak force, ms
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Rise time, ms
Isotonic Peak velocity, Had-s: Peak power, d-s: Average power, J's" Time to peak velocity, ms Rise time, ms
Day 1
Squat Day 2
2074.1 (557.10) 400.3 (173.61) 365.2 (119.08) 269.3 (90.08) 1328.5 (257.71) 773.1 (251.61)
2126.3 (560.03) 398.6 (165.72) 375.8 (156.76) 276.7 (115.18) 1399.7 (642.88) 689.4 (218.52)
0.92 (0.206) 1119.2 (423.36) 760.7 (246.22) 469.4 (73.77) 496.5 (94.66)
0.95 (0.202) 1104.6 (343.64) 759.4 (232.13) 453.2 (111.46) 485.1 (101.22)
%~
Day1
Bench Press Day 2
2.5
1031.8 (329.07) 255.2 (95.11) 178.3 (68.55) 139.7 (55.43) 1725.4 (391.87) 1331.2 (409.76)
1042.7 (332.11) 261.3 (102.29) 178.2 (64.57) 139.6 (49.09) 1722.4 (435.17) 1330.9 (432.91)
0.91 (0.145) 479.6 (168.71) 309.7 (107.85) 735.1 (258.61) 508.3 (111.47)
0.95 (0.137) 530.5 (193.56) 331.3 (120.07) 711.9 (255.99) 516.5 (114.59)
-0.4 2.9 2.7 5.4 -10.8*
3.3 -1.3 -0.2 -3.5 -2.3
%~
1.1 2.4 0.0 0.0 0.2 0.0
4.4* 10.6* 7.0* -3.2 1.6
*Significant difference between the means for Days 1 and 2; paired t-test (p .OS,one-way ANOVAwithrepeatedmeasures). For isokineticBP (seeFigure I C), therewasalsoa significant
trials effect across days without a days effect. Although the trialseffectdid notoffsetthe reliability of this measure, it did indicate the possibility of a "measurementschedule effect" (Kroll, 1970). An alternativethat would improve the current protocol would be to allow for longer rest periods between trialsandsetsor to useonlyonesetof onetrialwithlongerrest intervals between sets. We believe that the decrement in performance for isokinetic BP (see Figure 1C) wasrelatedto the smallermusclemassof the upperextremities in comparisonto SQexercisewhereperformance wasmorestableacross sets (seeFigure lA). Concerning the days x trialsinteraction for isotonicSQ (see Figure lB), removalof the unstable first trial on both days eliminated the significant interaction (F= 1.67;p> .05,two-way ANOVAwithrepeatedmeasures). Figure ID demonstrates that there wasa smallbut significant dayseffectforisotonicBPexercise.Wehavenologicalexplanationwhythisoccurred. The scoresonDay2 werehigherby an averageof 3.5% (P< .05),but an ordereffectwas unlikely because testing sequence was balanced across exercises, subjects, and test days. While muscular performance may increaseunderrepeatedtestconditionsduetolearning (Henry, 1942; Schenck & Forward, 1965) or reminiscence (Sage, 1984), such factors cannot explain why subjectsperformed
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Table 2 Intraclass Correlations for the Mechanical Characteristics of lsoklnetlc and Isotonic Squat and Bench Press Exercise Isokinetic Squat Bench 0.928· 0.890 0.893 0.695 0.816 t
Repetition work Peak power Average power Time to peak Rise time
0.817· 0.911 0.951 0.910 0.919·
better on the second testing day for only 1 of the 4 exercise modes. For isotonic BP, at least 8 prior trials over 2 days were apparently needed before stabilization occurred. Indeed, there was no significant days effect for the last set of exercise over the 2 test days (F = 1.11; p > .05; one-way ANOYA with repeated measures). In summary, a computerizeddynamometer has been used to assess reliability of multijoint upper and lower body muscular performance for 11 criterion measures. Day-to-day variabilityforallmeasuresrangedbetween-1O.8%andlO.6%; there was also stability in the reliability coefficients for multiple scores across days. In addition to the conventional measures of peak force and velocity, reliability was also evaluated for other muscle mechanical characteristics, which included time to peak force, time to peak velocity, rise time. power, and work output. Reliability exceeded R =.85 in 6 of the 11 computer generated scores. Thus, we conclude that
Isotonic Squat Bench _II 0.936· 0.880 0.878' 0.920
0.970t 0.971 ot' 0.774 0.794
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IINot measured ·Significant Trials effect (p < .05). tSignificant Days effect (p < .05). 'Significant Days x Trials interaction (p < .05).
A. Isokinetic Squat 200
Set 1
Set 2
190 :.
...=
-"
180
~
;Z
-s
170
:.J l.
B. Isotonic Squat
~ ~
150
012
3
~ ~
~
....
0.8
.~
I:
456
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y
789
0.7
2
0
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c.
...=
100
~
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90
~
4
/:
6
8
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10
12
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Set 2
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110
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~
Day 1 Day 2
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e 160
~
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80
o
R = 0.861 Days: F = 0.74 Trials: F = 8.73* D X T: F = 1.36 1
-0-
---
234
e ;;>~
Day 1 Day 2
5
0.7
0
6
R = 0.959 Days: F = 5.07* Trials: F = 1.66 D X T: F = 1.10 2
4
-0-
--6
8
Day 1 Day 2
10
I 12
Repetitions
Repetitions
Figure 1. Mean values for 24 males tested on two days for lsoklnetlc squat (A), Isotonic squat (B), Isoklnetlc bench press (C), and Isotonic bench press (D). The Insert Includes the Intraclass R, and the Fratlos for days, trials, and Interaction. ·slgnlflcant effect (p < .05). RBsIlAllCH QuARTIlRLY POR ExERCISB AND SPORT, VOL.
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muscle mechanical characteristics for the squat and bench press can be reliably assessed with the multifunction dynamometer.
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References Agre, J. C., Magness, J. L., Hull, S. Z., Wright, K. C., Baxter, T. L., Patterson, R., & Stradel, L. (1987). Strength testing with a portable dynamometer: Reliability for upper and lower extremities. Archives ofPhysical Medicine andRehabilitation, 68, 454-458. Burdett, R. G., & Van Swearingen, 1.(1987). Reliability ofisokinetic muscle endurance tests. JourTI/JI of Orthopaedic and Sports Physical Therapy, 8, 484-488. Farrel, M., & Richards, J. G. (1986). Analysis of the reliability and validity of the kinetic communicator exercise device. Medicine and Science in Sports and Exercise, 18, 44-49. Feldt, L. S., & McKee, M. E. (1958). Estimation of reliability of skill tests. Research Quarterly, 29, 279-293. Haggard, E. A. (1958). Intraclass correlation and the analysis of variance. New York: Dryden. Henry, F. (1942). The practice and fatigue effects in the Sargent test. Research Quarterly,l3, 16-29. Jacobs, I., & Pope, 1. (1986). A computerized system for muscle strengthevaluation: Measurementreproducibility, validity, and some normative data. National Strength and Conditioning Association Journal, 8, 28-33. Johnson, J., & Siegel, D. (1978). Reliability of an isokinetic movement of the knee extensors. Research Quarterly, 49, 88-92. Knapik, 1.1., & Ramos, M. U. (1980). Isokinetic and isometric torque relationships in the human body. Archives ofPhysical Medicine and Rehabilitation, 61, 64-67. Knapik, J. J., Wright, J. E., Mawdsley, R. H., & Brawn, J. (1983). Isometric, isotonic, and isokinetic torque variations in four musclegroups through a range ofmotion. PhysicalTherapy, 63, 938-947. Kroll, W. (1964). Reliability variations of strength in test-retest situations. Research Quarterly, 34, 50-56.
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Kroll, W. (1970). Test reliability and errors of measurement at several levels of absolute isometric strength. Research Quarterly,41,155-162. Moffroid, M., Whipple, R., Hofkosh, 1., Lowman, E., & Thistle, H. (1969). A study of isokinetic exercise. Physical Therapy, 49, 735-746. Nelson, R. C., & Fahrney, R. A. (1965). Relationship between strength and speed of elbow flexion. Research Quarterly, 36, 455-463. Osternig, L. R., Bates, B. T., & James, S. L. (1977). Isokinetic and isometric torque force relationships. Archives of Physical Medicine and Rehabilitation, 58, 254-257. Safrit, M. 1., Atwater, A. E., Baumgartner, T. A., & West, C. (1976). Reliability Theory. Washington, DC: American Alliance for Health, Physical Education, and Recreation. Sage, G. H. (1984). Motor learning and control. Dubuque, IA: W.C. Brown Publishers. Schenck, J. M., & Forward, E. M. (1965). Quantitative strength changes with test repetitions. Physical Therapy, 45,562-569. Thistle, H. G., Hislop, H. 1.,Moffroid,M., & Lowman, E. W. (1967). Isokinetic contraction: A new concept of resistive exercise. ArchivesofPhysicalMedicine and Rehabilitation, 48,279-282.
Authors' Note This research was supported in part by a grant from HydraFitness Industries, Belton, TX. Appreciation is extended to P. F. LaChance for his expertise with data collection.
Submitted: August 19,1988 Accepted: April 16, 1989 Tibor Hortobagyi is an adjunctprofessorin theDepartment of Sport Science/Biology, 2000 S. Gaylord, University of Denver,Denver,CO80210.Frankl. Katchis aprofessor and the chairman oftheDepartment ofExercise Science, University ofMassachusetts, Amherst, MA 01003.
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