Journal of Gerontology: MEDICAL SCIENCES 1991, Vol.46, No. 2, M47-51
Copyright 1991 by The Geronlological Society of America
Reliability of Isometric Hip Abductor Torques During Examiner- and Belt-Resisted Tests John F. Kramer,1 Margaret D. Vaz,2 and Anthony A. Vandervoort1 'Department of Physical Therapy, University of Western Ontario. 2 University Hospital, London, Ontario.
in the hip musculature is a common feature WEAKNESS of many conditions that impair mobility (e.g., osteoarthritis, bedrest, stroke) in elderly individuals. Periodic assessment of muscle strength (defined as the ability of muscles to produce tension) is considered to be an essential component in planning, modifying, and progressing patient treatment programs during rehabilitation (1,2). Although manual muscle testing (MMT) is an inexpensive, relatively quick and convenient method for assessing muscle strength, the subjective grading systems that are most frequently used may produce divergent scores and require relatively large changes in patient status in order to detect strength changes (2-4). For example, Beasley (3), when studying children with poliomyelitis, commented that MMT could not distinguish between knee extension forces that differed by as much as 25%. Wads worth et al. (1) noted that while MMT and hand-held dynamometers (HHD) could both produce reliable measurements, the MMT scale lacked sensitivity. As a result, for two of five muscle groups examined, the subjects scored the same on the test and the retest. Consequently, a Pearson Product Moment Correlation could not be calculated for the MMT. Bohannon et al. (4) concluded that although there was a strong relationship between MMT and HHD assessments of knee extension forces, the lack of precision associated with MMT could grossly overestimate patient strength. As a result, there has been an increased interest in the use of instruments that provide objective and more precise measurements, such as computerized dynamometers, strain gauges, HHDs, load-cell devices, and modified sphygmomanometers. With the increased emphasis on quantification of muscular capability and the use of HHDs, the comparability of different test protocols — including differences in positioning, stabilization, and the method of applying external forces
to the body segment — becomes increasingly important (1,3,5,6). For example, Byl et al. (7) reported that as stabilization increased, so did the strength measurements recorded. When using examiner-resisted tests, the physical effort and the degree of stabilization that must be provided by the examiner increase as the subject's strength capability increases. As a result, unless adequate stabilization is provided, reliability may decrease as muscular capability increases (1,8,9). Precise measurements of hip abductor strength are confounded by a number of factors. Many elderly individuals, even without hip or knee pathology, cannot be positioned in side-lying for unilateral, anti-gravity tests of the hip abductors (10). Standing tests may be impractical due to opposite limb involvement or poor balance. Trunk leaning and hip hiking may be used to substitute for hip abductor strength, regardless of the test position. The degree to which the hip abductors on the nontest side are required to prevent pelvic rotation (in the coronal plane) toward the test side, or may substitute for the hip abductors on the test side by rotating the pelvis toward the nontest side, is unclear. For these reasons, test protocols which maximize stabilization, reduce the physical requirement of the tester, are practical for a wide range of patients, and produce reliable scores merit study. The purposes of this study were to determine the testretest reliability of isometric hip abductor torques in elderly subjects, to compare an examiner-resisted and a belt-resisted test protocol, and to compare the performances of elderly and young subjects. Little information is currently available regarding strength capability of the hip abductors or how elderly and young females compare on reliability of performance. The examiner- and the belt-resisted methods are two clinically practical techniques for assessment of hip abductor strength using a HHD. The belt-resisted method was thought M47
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The purposes of this study were to determine the test-retest reliability of isometric hip abductor torques in elderly females, to compare two assessment protocols, and to compare the performances of elderly and young females. Twenty elderly and 20 young women were tested on two occasions. During the examiner-resisted test the examiner provided the resistance, and during the belt-resisted test the subject's contralateral leg provided the resistance while the examiner positioned the dynamometer. A four-way ANOVA indicated no occasion effects (p > .05). Within each group, similar torques were produced by both legs (p > .05). Test-retest intraclass reliability coefficients were goodto-high, rangingfrom 0.84 to 0.98 for the eight combinations of group-method-leg. The elderly females produced 61% of the torques produced by young females (p < .01), and the examiner-resisted method produced 65% of the torques produced using the belt-resisted method (p < .01). The belt-resisted method required less physical effort on the part of the tester, provided greater stabilization of the pelvis, and was preferred by 95% of the subjects.
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KRAMER ET AL.
to offer applicability to a wide range of subjects and greater stability, to produce greater hip abductor torques, and to allow one examiner to easily provide sufficient resistance while performing the test.
scores during two applications of the HHD at the same strain gauge force. Validity and stability coefficents of 0.99 were observed at the start and finish of this 6-week study (12,13). The HHD was used only for testing within the present study in order to maximize accuracy and reliability (14).
METHODS
General outline. — Each subject was tested on two separate occasions of about 10 minutes duration, separated by a 30-minute rest period. The two test occasions were completed on one day in order to minimize the individual subjects' inconvenience and time commitments to the study. The order of testing the right and left legs and using the beltresisted and examiner-resisted tests was randomly assigned. Following a verbal description of the test procedures, at least two submaximal and one maximal contractions were completed as practice prior to data acquisition. Any subject requesting additional practices was allowed to do so. Following 2 minutes rest, three maximal test contractions were recorded. All contractions were of about 4 seconds duration and were completed about 45 seconds apart. The subjects gradually increased their force against the HHD (examinerresisted test) or spread their legs apart (belt-resisted test) until they had reached their maximum, termed a "make" test (11). All testing was completed using a new Spark hand-held dynamometer (Spark Instruments and Academics, Inc., Coralville, IA). The accuracy and reliability of this HHD were determined by comparing the forces recorded by the HHD with those registered by a strain gauge, for 15 applications by the tester. During these determinations, the tester applied a force through the HHD vertically downward against the strain gauge while an assistant noted the highest force recorded by the strain gauge system. Accuracy (validity coefficient) was determined by comparing the HHD score with that indicated by the strain gauge system; the reliability (stability coefficent) was determined by comparing the Table 1. Descriptive Data for Young and Elderly Females, M and (SD) Group Elderly (n = 20) Young (n = 20)
Age (yr)
Height (m)
Weight (kg)
68.4(5.2)
1.62(0.07)
62.3 (9.5)
23.5(3.4)
1.64(0.06)
57.5(6.4)
Test positions. — The subject was positioned supine on a plinth with both legs abducted about 10°, as measured by a goniometer. A strap (5 cm wide) was positioned around the plinth and over the subject's pelvis, thereby providing some stabilization of the pelvis on the plinth. During the examiner-resisted test, the subject pushed against the HHD as the examiner alone provided the resistance, stabilizing and positioning the HHD (Figure 1). During the belt-resisted test, the examiner positioned the HHD, but did not herself provide active resistance (Figure 2). A second belt (5 cm width) was placed around the legs, just proximal to the knees. The HHD was positioned between the belt and the side of the test leg, so that abduction of the legs compressed the dynamometer between the belt and the leg. During the belt-resisted test, subjects were instructed to spread their legs apart simultaneously, as hard as possible. Both the examiner-resisted and the belt-resisted tests were "make," rather than "break" tests (11). The subjects gradually built up tension for 2-3 seconds, pushed as hard as possible for at least 1 second against the dynamometer, and then stopped when they had done so. The HHD recorded the highest resistance force during the contraction. The distance from the greater trochanter to the point of dynamometer contact with the leg was measured. For each subject, the same distance was used for both legs and on both occasions. The dynamometer moment arm relative to the hip axis was later determined by adding 4 cm to the distance from the greater trochanter to the point of resistance application, in order to provide a more accurate estimate of moment arm length from the hip rotational axis (15). Because the direction of hip abduction was in the horizontal plane and the leg was supported by the plinth, the leg segment torque did not provide resistance to hip abduction (16). As a result, the dynamometer (resistance) torque equalled the hip abductor (effort) torque (16). Immediately following the second test occasion the subjects were asked which test method they preferred and why. Data analysis. — The three test repetitions for each of the four combinations of leg and test were averaged to provide a single torque score for each occasion. Intraclass correlation coefficients (Type 2,1) were calculated using a 2-way analysis of variance (ANOVA) model (13). These ICCs indicate the reliability of any one occasion. A 4-way ANOVA procedure (two groups by two test methods by two legs by two occasions) with repeated measures on the last three factors was used to test the hip abductor torques for statistically significant differences (17). Following significant F-ratios, a Newman-Keuls technique was used to compare selected pairs of means (17). The .05 level was adopted as the maximum probability level denoting statistically significant differences.
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Subjects. —Two groups (n = 20 each) of healthy women with no previous history of pathology to either leg gave informed consent to participate (see Table 1 for descriptive information). The younger women (mean age 24 yr) were university students and physical therapists, while the elderly women (mean age 68 yr) were volunteers from the university senior alumni. Although none of the young women was involved in competitive athletics, the majority participated in activities such as jogging or exercise classes two or more times per week. All of the elderly women reported that they exercised three or more times per week via walking, swimming, or playing golf.
HIP ABDUCTOR TORQUES
RESULTS
Tables 2 and 3 summarize the hip abductors torques and the results of the ANOVA. No significant occasion effects were observed on the ANOVA. All ICCs were 0.84 or greater (Table 4) and are considered to reflect good-to-high reliability, where 0.80-0.89 indicates good reliability and 0.90 to 0.99 indicates high reliability (18). Only the Group x Method x Leg interaction (p < .03), and the group and method main effects (p < .01) were significant on the ANOVA. Post hoc analysis of the interaction indicated no significant differences between right and left legs for either group (p > .05). Within each group, the belt-resisted method produced significantly higher torques than did the examiner-resisted method for both legs (p < .01). Within both the belt- and examiner-resisted tests, the elderly subjects produced significantly lower torques than did the young subjects, with both legs (p < .01). However, the torques produced by the elderly females using the beltresisted method did not differ significantly from those produced by the young females when using the examinerresisted method (p > .05). Thirty-eight subjects (95% of the group) preferred the belt-resisted method of testing. These subjects stated that they felt more stable and were, therefore, able to produce a
Figure 2. Belt-resisted test of hip abductor strength provided by the belt around both legs.
the resistance is
Table 2. Hip Abductor Torques (Nm) for Elderly and Young Females Using Belt-Resisted and Examiner-Resisted Tests, M and (SD) Right Hip
Left Hip
Test Method
Occasion 1
Occasion 2
Occasion 1
Occasion 2
(it = 20)
Belt Examiner
49(22) 29(13)
50 (23) 30(13)
49(21) 31(12)
49(21) 30(13)
Young (n = 20)
Belt Examiner
77(17) 54(17)
77(18) 50(15)
78(16) 52(17)
78(18) 50(16)
Group Elderly
stronger contraction using the belt-resisted method. None of the subjects reported either test method to be uncomfortable. DISCUSSION
Both young and elderly subjects produced reliable hip abductor torques in the present study. This observation agrees with previous work by Neumann et al. (19), who reported that 12 young subjects produced test-retest (one week apart) Pearson Product Moment Correlation Coefficients greater than 0.93, when averaged over six hip angles.
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Figure 1. Examiner-resisted test of hip abductor strength — the examiner provides the resistance.
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HIP ABDUCTOR TORQUES
2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24.
ACKNOWLEDGMENT
25.
Address correspondence to Dr. John Kramer, Department of Physical Therapy, Faculty of Applied Health Sciences, Elborn College, University of Western Ontario, London, Ontario, Canada N6G 1H1.
26.
REFERENCES
1. Wadsworth CT, Krishnan R, Sear M, Harrold J, Nielsen DH. Intrarater
reliability of manual muscle testing and hand-held dynametric muscle testing. Phys Ther 1987;67:1342-7. Frese E, Brown M, Norton BJ. Clinical reliability of manual muscle testing: middle trapezius and gluteus medius muscle. Phys Ther 1987;67:1072-6. Beasley WC. Influence of method on estimates of normal knee extensor force among normal and postpolio children. Phys Ther Rev 1956;36:21-41. Bohannon RW. Manual muscle test scores and dynamometer test scores of knee extension strength. Arch Phys Med Rehabil 1986; 67:390-2. Rothstein JM. Measurement in clinical practice: theory and application. In Rothstein JN, ed. Measurement in physical therapy: clinics in physical therapy. New York: Churchill Livingstone, 1985:8-9. Smidt GL, Rogers MW. Factors contributing to the regulation and clinical assessment of muscular strength. Phys Ther 1982;62:1283-90. Byl NN, Richards S, Asturias J. Intrarater and interrater reliability of strength measurements of the biceps and deltoid using a hand-held dynamometer. J Orthop Sports Phys Ther 1988;9:399^05. Riddle DL, Finucane SD, Rothstein JM, Walker ML. Intrasession and intersession reliability of hand-held dynamometer measurements taken on brain-damaged patients. Phys Ther 1989;69:182-9 Bohannon RW, Andrews AW. Interrater reliability of hand-held dynamometry. Phys Ther 1987;67:931-7. Cahalan TD, Johnson ME, Liu S, Chao EYS. Quantitative measurements of hip strength in different age groups. Clin Orthop 1989; 246:136-45. Bohannon RW. Make tests and break tests of elbow flexor muscle strength. Phys Ther 1988;68:193-4. Ghiselli EE, Campbell JP, Zedeck S. Measurement theory for the behavioral sciences. San Francisco: WH Freeman, 1981. Shrout PE, Fleiss JL. Intraclass correlations: uses in assessing rater reliability. Psychol Bull 1979;86:420-8. Bohannon RW, Andrews AW. Accuracy of spring and strain gauge hand-held dynamometers. J Orthop Sports Phys Ther 1989; 11:323-6. Plagenhoef S. Patterns of human motion: a cinematographic analysis. Englewood Cliffs, NJ: Prentice-Hall, 1971. LeVeau B. Williams and Lissner: Biomechanics of human motion. 2nd ed. Toronto: W.B. Saunders, 1977. Winer BJ. Statistical principles in experimental design. 2nd ed. Toronto: McGraw-Hill, 1971. Currier, DP. Elements of research in physical therapy. 2nd ed. Baltimore: Waverly Press, 1984:162. Neumann DA, Soderberg GL, Cook TM. Comparison of maximal isometric hip abductor muscle torques between sides. Phys Ther 1988;68:496-502. Murray MP, Sepic BS. Maximum isometric torque of hip abductor and adductor muscles. Phys Ther 1969;48:1327-35. Burnett CN, Bitts EF, King W. Reliability of isokinetic measurements of hip muscle torque in young boys. Phys Ther 1990;70:244—9. Jensen RH, Smidt GL, Johnston RC. A technique for obtaining measurements of force generated by hip muscles. Arch Phys Med Rehabil 1971;52:207-15. Markhede G, Grimby G. Measurement of strength of hip joint muscles. Scand J Rehab Med 1980; 12:169-74. May WW. Relative isometric force of the hip abductor and adductor muscles. Phys Ther 1968;48:845-51. Vandervoort AA, Kramer JF, Wharram ER. Eccentric knee strength of elderly females. J Gerontol Biol Sci 1990;45:B 125-8. Cummins SR, Nevitt MC. A hypothesis: the causes of hip fractures. J Gerontol Med Sci 1989;44:M 107-11.
Received February 15, 1990 Accepted June 11, 1990
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tors. Complete or absolute isolation of unilateral hip abductors may not be feasible in most clinical test situations, where elaborate pelvic fixation designed to eliminate any contribution from the nontest hip abductors in stabilizing the pelvis is impractical. We believe that this limitation applies to the belt-resisted method as well as to most other clinically practical means of assessing hip abductor strength. The observation of no significant difference between the two legs of our healthy subjects is in agreement with May (24), who used a hydraulic system and tested in both supine and standing positions, and with Murray and Sepic (20), who used bilateral cable tensiometer tests performed in supine. Neumann et al. (19), however, observed a tendency for young right-handed subjects to score significantly higher on right hip abductor torques (side main effect, averaged over six test angles) and for the torque-hip angle slopes to differ between sides. They tested in the supine position using force transducers and detailed stabilization techniques. These observations, and our findings that when comparing the elderly subjects tested via the belt-resisted method to the young subjects tested via the examiner-resisted method no hip abductor strength difference was observed, further suggest that hip assessments are protocol specific. Murray and Sepic (20) reported that middle-aged women (40-55 yr) produced 83% of the hip abductor torques of young women (18-33 yr). In the present study, the elderly women (mean age 68 yr) produced 61% of the hip abductor torques of the young group (mean age 24 yr). Because the elderly group in the present study weighed about 8% more than the young women, the difference between the groups would have been even greater if relative torques (Nm/kg) had been used as the criterion measurement. We have observed similar strength deficits during isokinetic tests at 45 and 907sec angular velocities: Elderly women (mean age 73 yr) produced knee extension and flexion torques ranging from 47 to 56% during concentric muscle actions, and from 62 to 76% during eccentric muscle actions of those torques produced by young women (mean age 25 yr) (25). Cummings and Nevitt (26) hypothesized that the hip abductors were not only important for their tension-producing capability, but also in absorbing potentially dangerous impact forces to the femur during falls. Although hip abductor and knee extensor-flexor strength are generally considered to be important during functional activities such as walking, the relationship between joint specific strength and functional activities requires further study.
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Copyright 1991 by The Geronlological Society of America
Reliability of Isometric Hip Abductor Torques During Examiner- and Belt-Resisted Tests John F. Kramer,1 Margaret D. Vaz,2 and Anthony A. Vandervoort1 'Department of Physical Therapy, University of Western Ontario. 2 University Hospital, London, Ontario.
in the hip musculature is a common feature WEAKNESS of many conditions that impair mobility (e.g., osteoarthritis, bedrest, stroke) in elderly individuals. Periodic assessment of muscle strength (defined as the ability of muscles to produce tension) is considered to be an essential component in planning, modifying, and progressing patient treatment programs during rehabilitation (1,2). Although manual muscle testing (MMT) is an inexpensive, relatively quick and convenient method for assessing muscle strength, the subjective grading systems that are most frequently used may produce divergent scores and require relatively large changes in patient status in order to detect strength changes (2-4). For example, Beasley (3), when studying children with poliomyelitis, commented that MMT could not distinguish between knee extension forces that differed by as much as 25%. Wads worth et al. (1) noted that while MMT and hand-held dynamometers (HHD) could both produce reliable measurements, the MMT scale lacked sensitivity. As a result, for two of five muscle groups examined, the subjects scored the same on the test and the retest. Consequently, a Pearson Product Moment Correlation could not be calculated for the MMT. Bohannon et al. (4) concluded that although there was a strong relationship between MMT and HHD assessments of knee extension forces, the lack of precision associated with MMT could grossly overestimate patient strength. As a result, there has been an increased interest in the use of instruments that provide objective and more precise measurements, such as computerized dynamometers, strain gauges, HHDs, load-cell devices, and modified sphygmomanometers. With the increased emphasis on quantification of muscular capability and the use of HHDs, the comparability of different test protocols — including differences in positioning, stabilization, and the method of applying external forces
to the body segment — becomes increasingly important (1,3,5,6). For example, Byl et al. (7) reported that as stabilization increased, so did the strength measurements recorded. When using examiner-resisted tests, the physical effort and the degree of stabilization that must be provided by the examiner increase as the subject's strength capability increases. As a result, unless adequate stabilization is provided, reliability may decrease as muscular capability increases (1,8,9). Precise measurements of hip abductor strength are confounded by a number of factors. Many elderly individuals, even without hip or knee pathology, cannot be positioned in side-lying for unilateral, anti-gravity tests of the hip abductors (10). Standing tests may be impractical due to opposite limb involvement or poor balance. Trunk leaning and hip hiking may be used to substitute for hip abductor strength, regardless of the test position. The degree to which the hip abductors on the nontest side are required to prevent pelvic rotation (in the coronal plane) toward the test side, or may substitute for the hip abductors on the test side by rotating the pelvis toward the nontest side, is unclear. For these reasons, test protocols which maximize stabilization, reduce the physical requirement of the tester, are practical for a wide range of patients, and produce reliable scores merit study. The purposes of this study were to determine the testretest reliability of isometric hip abductor torques in elderly subjects, to compare an examiner-resisted and a belt-resisted test protocol, and to compare the performances of elderly and young subjects. Little information is currently available regarding strength capability of the hip abductors or how elderly and young females compare on reliability of performance. The examiner- and the belt-resisted methods are two clinically practical techniques for assessment of hip abductor strength using a HHD. The belt-resisted method was thought M47
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The purposes of this study were to determine the test-retest reliability of isometric hip abductor torques in elderly females, to compare two assessment protocols, and to compare the performances of elderly and young females. Twenty elderly and 20 young women were tested on two occasions. During the examiner-resisted test the examiner provided the resistance, and during the belt-resisted test the subject's contralateral leg provided the resistance while the examiner positioned the dynamometer. A four-way ANOVA indicated no occasion effects (p > .05). Within each group, similar torques were produced by both legs (p > .05). Test-retest intraclass reliability coefficients were goodto-high, rangingfrom 0.84 to 0.98 for the eight combinations of group-method-leg. The elderly females produced 61% of the torques produced by young females (p < .01), and the examiner-resisted method produced 65% of the torques produced using the belt-resisted method (p < .01). The belt-resisted method required less physical effort on the part of the tester, provided greater stabilization of the pelvis, and was preferred by 95% of the subjects.
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KRAMER ET AL.
to offer applicability to a wide range of subjects and greater stability, to produce greater hip abductor torques, and to allow one examiner to easily provide sufficient resistance while performing the test.
scores during two applications of the HHD at the same strain gauge force. Validity and stability coefficents of 0.99 were observed at the start and finish of this 6-week study (12,13). The HHD was used only for testing within the present study in order to maximize accuracy and reliability (14).
METHODS
General outline. — Each subject was tested on two separate occasions of about 10 minutes duration, separated by a 30-minute rest period. The two test occasions were completed on one day in order to minimize the individual subjects' inconvenience and time commitments to the study. The order of testing the right and left legs and using the beltresisted and examiner-resisted tests was randomly assigned. Following a verbal description of the test procedures, at least two submaximal and one maximal contractions were completed as practice prior to data acquisition. Any subject requesting additional practices was allowed to do so. Following 2 minutes rest, three maximal test contractions were recorded. All contractions were of about 4 seconds duration and were completed about 45 seconds apart. The subjects gradually increased their force against the HHD (examinerresisted test) or spread their legs apart (belt-resisted test) until they had reached their maximum, termed a "make" test (11). All testing was completed using a new Spark hand-held dynamometer (Spark Instruments and Academics, Inc., Coralville, IA). The accuracy and reliability of this HHD were determined by comparing the forces recorded by the HHD with those registered by a strain gauge, for 15 applications by the tester. During these determinations, the tester applied a force through the HHD vertically downward against the strain gauge while an assistant noted the highest force recorded by the strain gauge system. Accuracy (validity coefficient) was determined by comparing the HHD score with that indicated by the strain gauge system; the reliability (stability coefficent) was determined by comparing the Table 1. Descriptive Data for Young and Elderly Females, M and (SD) Group Elderly (n = 20) Young (n = 20)
Age (yr)
Height (m)
Weight (kg)
68.4(5.2)
1.62(0.07)
62.3 (9.5)
23.5(3.4)
1.64(0.06)
57.5(6.4)
Test positions. — The subject was positioned supine on a plinth with both legs abducted about 10°, as measured by a goniometer. A strap (5 cm wide) was positioned around the plinth and over the subject's pelvis, thereby providing some stabilization of the pelvis on the plinth. During the examiner-resisted test, the subject pushed against the HHD as the examiner alone provided the resistance, stabilizing and positioning the HHD (Figure 1). During the belt-resisted test, the examiner positioned the HHD, but did not herself provide active resistance (Figure 2). A second belt (5 cm width) was placed around the legs, just proximal to the knees. The HHD was positioned between the belt and the side of the test leg, so that abduction of the legs compressed the dynamometer between the belt and the leg. During the belt-resisted test, subjects were instructed to spread their legs apart simultaneously, as hard as possible. Both the examiner-resisted and the belt-resisted tests were "make," rather than "break" tests (11). The subjects gradually built up tension for 2-3 seconds, pushed as hard as possible for at least 1 second against the dynamometer, and then stopped when they had done so. The HHD recorded the highest resistance force during the contraction. The distance from the greater trochanter to the point of dynamometer contact with the leg was measured. For each subject, the same distance was used for both legs and on both occasions. The dynamometer moment arm relative to the hip axis was later determined by adding 4 cm to the distance from the greater trochanter to the point of resistance application, in order to provide a more accurate estimate of moment arm length from the hip rotational axis (15). Because the direction of hip abduction was in the horizontal plane and the leg was supported by the plinth, the leg segment torque did not provide resistance to hip abduction (16). As a result, the dynamometer (resistance) torque equalled the hip abductor (effort) torque (16). Immediately following the second test occasion the subjects were asked which test method they preferred and why. Data analysis. — The three test repetitions for each of the four combinations of leg and test were averaged to provide a single torque score for each occasion. Intraclass correlation coefficients (Type 2,1) were calculated using a 2-way analysis of variance (ANOVA) model (13). These ICCs indicate the reliability of any one occasion. A 4-way ANOVA procedure (two groups by two test methods by two legs by two occasions) with repeated measures on the last three factors was used to test the hip abductor torques for statistically significant differences (17). Following significant F-ratios, a Newman-Keuls technique was used to compare selected pairs of means (17). The .05 level was adopted as the maximum probability level denoting statistically significant differences.
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Subjects. —Two groups (n = 20 each) of healthy women with no previous history of pathology to either leg gave informed consent to participate (see Table 1 for descriptive information). The younger women (mean age 24 yr) were university students and physical therapists, while the elderly women (mean age 68 yr) were volunteers from the university senior alumni. Although none of the young women was involved in competitive athletics, the majority participated in activities such as jogging or exercise classes two or more times per week. All of the elderly women reported that they exercised three or more times per week via walking, swimming, or playing golf.
HIP ABDUCTOR TORQUES
RESULTS
Tables 2 and 3 summarize the hip abductors torques and the results of the ANOVA. No significant occasion effects were observed on the ANOVA. All ICCs were 0.84 or greater (Table 4) and are considered to reflect good-to-high reliability, where 0.80-0.89 indicates good reliability and 0.90 to 0.99 indicates high reliability (18). Only the Group x Method x Leg interaction (p < .03), and the group and method main effects (p < .01) were significant on the ANOVA. Post hoc analysis of the interaction indicated no significant differences between right and left legs for either group (p > .05). Within each group, the belt-resisted method produced significantly higher torques than did the examiner-resisted method for both legs (p < .01). Within both the belt- and examiner-resisted tests, the elderly subjects produced significantly lower torques than did the young subjects, with both legs (p < .01). However, the torques produced by the elderly females using the beltresisted method did not differ significantly from those produced by the young females when using the examinerresisted method (p > .05). Thirty-eight subjects (95% of the group) preferred the belt-resisted method of testing. These subjects stated that they felt more stable and were, therefore, able to produce a
Figure 2. Belt-resisted test of hip abductor strength provided by the belt around both legs.
the resistance is
Table 2. Hip Abductor Torques (Nm) for Elderly and Young Females Using Belt-Resisted and Examiner-Resisted Tests, M and (SD) Right Hip
Left Hip
Test Method
Occasion 1
Occasion 2
Occasion 1
Occasion 2
(it = 20)
Belt Examiner
49(22) 29(13)
50 (23) 30(13)
49(21) 31(12)
49(21) 30(13)
Young (n = 20)
Belt Examiner
77(17) 54(17)
77(18) 50(15)
78(16) 52(17)
78(18) 50(16)
Group Elderly
stronger contraction using the belt-resisted method. None of the subjects reported either test method to be uncomfortable. DISCUSSION
Both young and elderly subjects produced reliable hip abductor torques in the present study. This observation agrees with previous work by Neumann et al. (19), who reported that 12 young subjects produced test-retest (one week apart) Pearson Product Moment Correlation Coefficients greater than 0.93, when averaged over six hip angles.
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Figure 1. Examiner-resisted test of hip abductor strength — the examiner provides the resistance.
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HIP ABDUCTOR TORQUES
2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24.
ACKNOWLEDGMENT
25.
Address correspondence to Dr. John Kramer, Department of Physical Therapy, Faculty of Applied Health Sciences, Elborn College, University of Western Ontario, London, Ontario, Canada N6G 1H1.
26.
REFERENCES
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reliability of manual muscle testing and hand-held dynametric muscle testing. Phys Ther 1987;67:1342-7. Frese E, Brown M, Norton BJ. Clinical reliability of manual muscle testing: middle trapezius and gluteus medius muscle. Phys Ther 1987;67:1072-6. Beasley WC. Influence of method on estimates of normal knee extensor force among normal and postpolio children. Phys Ther Rev 1956;36:21-41. Bohannon RW. Manual muscle test scores and dynamometer test scores of knee extension strength. Arch Phys Med Rehabil 1986; 67:390-2. Rothstein JM. Measurement in clinical practice: theory and application. In Rothstein JN, ed. Measurement in physical therapy: clinics in physical therapy. New York: Churchill Livingstone, 1985:8-9. Smidt GL, Rogers MW. Factors contributing to the regulation and clinical assessment of muscular strength. Phys Ther 1982;62:1283-90. Byl NN, Richards S, Asturias J. Intrarater and interrater reliability of strength measurements of the biceps and deltoid using a hand-held dynamometer. J Orthop Sports Phys Ther 1988;9:399^05. Riddle DL, Finucane SD, Rothstein JM, Walker ML. Intrasession and intersession reliability of hand-held dynamometer measurements taken on brain-damaged patients. Phys Ther 1989;69:182-9 Bohannon RW, Andrews AW. Interrater reliability of hand-held dynamometry. Phys Ther 1987;67:931-7. Cahalan TD, Johnson ME, Liu S, Chao EYS. Quantitative measurements of hip strength in different age groups. Clin Orthop 1989; 246:136-45. Bohannon RW. Make tests and break tests of elbow flexor muscle strength. Phys Ther 1988;68:193-4. Ghiselli EE, Campbell JP, Zedeck S. Measurement theory for the behavioral sciences. San Francisco: WH Freeman, 1981. Shrout PE, Fleiss JL. Intraclass correlations: uses in assessing rater reliability. Psychol Bull 1979;86:420-8. Bohannon RW, Andrews AW. Accuracy of spring and strain gauge hand-held dynamometers. J Orthop Sports Phys Ther 1989; 11:323-6. Plagenhoef S. Patterns of human motion: a cinematographic analysis. Englewood Cliffs, NJ: Prentice-Hall, 1971. LeVeau B. Williams and Lissner: Biomechanics of human motion. 2nd ed. Toronto: W.B. Saunders, 1977. Winer BJ. Statistical principles in experimental design. 2nd ed. Toronto: McGraw-Hill, 1971. Currier, DP. Elements of research in physical therapy. 2nd ed. Baltimore: Waverly Press, 1984:162. Neumann DA, Soderberg GL, Cook TM. Comparison of maximal isometric hip abductor muscle torques between sides. Phys Ther 1988;68:496-502. Murray MP, Sepic BS. Maximum isometric torque of hip abductor and adductor muscles. Phys Ther 1969;48:1327-35. Burnett CN, Bitts EF, King W. Reliability of isokinetic measurements of hip muscle torque in young boys. Phys Ther 1990;70:244—9. Jensen RH, Smidt GL, Johnston RC. A technique for obtaining measurements of force generated by hip muscles. Arch Phys Med Rehabil 1971;52:207-15. Markhede G, Grimby G. Measurement of strength of hip joint muscles. Scand J Rehab Med 1980; 12:169-74. May WW. Relative isometric force of the hip abductor and adductor muscles. Phys Ther 1968;48:845-51. Vandervoort AA, Kramer JF, Wharram ER. Eccentric knee strength of elderly females. J Gerontol Biol Sci 1990;45:B 125-8. Cummins SR, Nevitt MC. A hypothesis: the causes of hip fractures. J Gerontol Med Sci 1989;44:M 107-11.
Received February 15, 1990 Accepted June 11, 1990
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tors. Complete or absolute isolation of unilateral hip abductors may not be feasible in most clinical test situations, where elaborate pelvic fixation designed to eliminate any contribution from the nontest hip abductors in stabilizing the pelvis is impractical. We believe that this limitation applies to the belt-resisted method as well as to most other clinically practical means of assessing hip abductor strength. The observation of no significant difference between the two legs of our healthy subjects is in agreement with May (24), who used a hydraulic system and tested in both supine and standing positions, and with Murray and Sepic (20), who used bilateral cable tensiometer tests performed in supine. Neumann et al. (19), however, observed a tendency for young right-handed subjects to score significantly higher on right hip abductor torques (side main effect, averaged over six test angles) and for the torque-hip angle slopes to differ between sides. They tested in the supine position using force transducers and detailed stabilization techniques. These observations, and our findings that when comparing the elderly subjects tested via the belt-resisted method to the young subjects tested via the examiner-resisted method no hip abductor strength difference was observed, further suggest that hip assessments are protocol specific. Murray and Sepic (20) reported that middle-aged women (40-55 yr) produced 83% of the hip abductor torques of young women (18-33 yr). In the present study, the elderly women (mean age 68 yr) produced 61% of the hip abductor torques of the young group (mean age 24 yr). Because the elderly group in the present study weighed about 8% more than the young women, the difference between the groups would have been even greater if relative torques (Nm/kg) had been used as the criterion measurement. We have observed similar strength deficits during isokinetic tests at 45 and 907sec angular velocities: Elderly women (mean age 73 yr) produced knee extension and flexion torques ranging from 47 to 56% during concentric muscle actions, and from 62 to 76% during eccentric muscle actions of those torques produced by young women (mean age 25 yr) (25). Cummings and Nevitt (26) hypothesized that the hip abductors were not only important for their tension-producing capability, but also in absorbing potentially dangerous impact forces to the femur during falls. Although hip abductor and knee extensor-flexor strength are generally considered to be important during functional activities such as walking, the relationship between joint specific strength and functional activities requires further study.
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