Relative Isometric Force of the Hip Abductor and Adductor Muscles

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1 Relative Isometric Force of the Hip Abductor and Adductor Muscles WARREN W. MAY, Captain, AMSC A-LTHOUGH THE CONCEPT of the muscular force curve is not new, its clinical application has been generally disregarded. Since 1948 numerous studies, using a variety of techniques and apparatus, have been done, but the development of satisfactory methods of quantitative evaluation applicable to the clinical situation has been limited However, evidence has been presented substantiating the need for and value of the quantitative approach in obtaining a more adequate concept of normal strength. REVIEW OF THE LITERATURE In a perusal of the literature only two studies were found that dealt with quantitative testing of the hip abductor muscle group; only one From the Physical Therapy Section, Brooke General Hospital, Brooke Army Medical Center, Fort Sam Houston, Texas. There is no expressed or implied Army approval of or preference for the products referred to in this paper over like or similar products of another company. Address for reprints: P.O. Box 112, Williamston, Michigan was found dealing with the hip adductor muscle group. Clarke reported force curves for hip abduction and adduction obtained from sixtyfour college men. 4 He tested only three angles in the range of motion with the subjects in a supine position. Both muscle groups exhibited a continuous decrease in strength as they were moved from the lengthened position. Williams and Stutzman presented force curves for hip abduction obtained from college age men and women. 20 The force was recorded at four points in the range of motion with the subjects in a side-lying position. The force curves obtained were found to decrease continuously from the lengthened position, and although the men exerted considerably more force in the lengthened position, the curves converged toward the end of the range. Since little information regarding the muscular forces of the hip abductor and adductor muscle groups has been presented in the literature, the present study was undertaken to obtain comprehensive data for these muscle groups of young adult males. Volume 48 / Number 8 845

ISOMETRIC FORCE OF HIP MUSCLES METHOD The data for the study were obtained from tests given to twenty-five clinically normal men twenty to twenty-eight years of age who were hospital personnel.

2 ISOMETRIC FORCE OF HIP MUSCLES METHOD The data for the study were obtained from tests given to twenty-five clinically normal men twenty to twenty-eight years of age who were hospital personnel. Height, weight, and dominance were recorded for each subject. The mean height of the group was inches, mean weight was pounds, and all but two of the subjects were right dominant. Measurement of thigh girth and length of the lower limb was also recorded but was not used for analysis in this study. Maximal isometric force of the hip abductor and adductor muscle groups was measured, to the nearest pound, by the use of a hydraulic muscular force testing table * (Fig. 1). * Designer and manufacturer: Michael Keropian, 683 Seventh Avenue, San Francisco, California Each subject was tested in two positions: supine and standing (Figs. 1, 2). The supine position was chosen because it is used for manual muscle testing, because it is used in exercising the hip abductor and adductor muscle groups, and because maximum stabilization can be provided. The standing position was chosen because it is the position of function, and because muscular force evaluation can be completed in a short time. In both test positions the hip was in the anatomical position of rotation, flexion, and extension; the knee was fully extended. Test Position and Stabilization The bilateral muscle groups were tested at four angles within the range of motion at intervals of 15 degrees (Figs. 3, 4). At the 0-degree test angle, which is the neutral position, the anterior midline of the femur was perpendicular to a line drawn between the anterior superior iliac spines. The other three Fig. 1. Force of right abductor muscles is being tested in supine test position with a hydraulic muscular force testing unit. 846 PHYSICAL THERAPY

3 test angles were then measured from the 0-degree angle with a double arm goniometer. The 15-degree test angle placed the muscle group in a lengthened position, the 15- and 30-degree angles in increasingly shortened positions. The four test angles were chosen to correspond to the portion of the range of motion used in manual muscle testing and manual exercise. Tests in the standing position were conducted only at the 0-degree test angle because lack of stabilization resulted at other angles. With the subject in either the supine or standing position, the assembly supporting the hydraulic gauge was positioned so that the lower edge of the gauge cuff could be placed against the medial or lateral aspect of the ankle approximately 1.5 inches above the medial malleolus and at a right angle to the leg. In the supine position a suspension cuff was used to support the weight of the leg. Stabilization in the supine position was pro- Fig. 2. Force of right abductor muscles is being tested in standing test position with a hydraulic muscular force testing unit. vided by: (1) bilateral shoulder cuffs, (2) a strap secured across the abdomen just above the anterior superior iliac spines, (3) a foot bar for the limb not being tested, (4) the subject's holding the sides of the table, and (5) the investigator, if necessary. In the standing position the only stabilization was provided by the subject's holding the side of the table. Each subject was instructed to hold onto the table, push steadily into the cuff with as much force and at as nearly a right angle as possible, then to relax. The command, "ready, pull, relax," was given in a normal tone of voice. The force at each angle was determined by computing the mean from the results of two attempts unless there was a difference of 5 or more pounds between the two trials. When this occurred, the subject was allowed a third attempt, and the three readings were averaged. At the angles in the range where the force recorded for the respective muscle groups was greatest, counterpressure was given against the gauge to prevent any movement of the apparatus, thus ensuring an isometric contraction. The sequence of angles tested was changed for each subject to minimize the effects of warm-up, learning, and fatigue. Analysis of Data Group data for the twenty-five subjects were analyzed to determine: 1. The difference in muscular force of the hip abductors and adductors on the dominant and nondominant sides in the two test positions. 2. The variation in muscular force of the abductors and adductors of the hip at selected angles within the range of joint motion in the supine test position. 3. The correlation between the force at each test angle and the composite force (sum of mean average forces from the four test angles) for each muscle group in the supine position. 4. The significance of the difference between the abductors and adductors at the four test angles in the supine position and at the 0-degree test angle in the standing position. 5. The angle in the range of hip motion where the force of the abductors and adductors was equal in the supine position. 6. The significance of the difference between the mean force at 0 degrees in the supine and standing position for both muscle groups. The 5 per cent level of confidence was used for all tests of significance. Volume 48 / Number 8 847

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4 t "is t i*\ 'n \, / I \ \? / I \ A i \ I I % '! i A \ ' / /?!/ Fig. 3. Test angles for abduction. v>w(\ \ t6' \ 30* Fig. 4. Test angles for adduction. PHYSICAL THERAPY

ISOMETRIC FORCE OF HIP MUSCLES RESULTS The difference between the mean average force of the abductors and adductors on the dominant sides for both test positions was not found to be statistically

5 ISOMETRIC FORCE OF HIP MUSCLES RESULTS The difference between the mean average force of the abductors and adductors on the dominant sides for both test positions was not found to be statistically significant. The data from the right and left abductor and adductor groups in each test position were then combined for further analysis (thus N=50). Table 1 shows the mean forces, standard deviations, and ranges for each of the test angles in the two test positions for the two muscle groups based on the combined data. Supine Abduction. Consistently greater force of hip abduction was recorded as the position of the muscle group changed from the shortened (30 ) angle to the lengthened ( 15 ) angle. The difference in force was pounds between the two angles. There was a significantly high correlation between the force at three of the test angles and the composite force. A correlation of.926,.696,.949, and.872 was found between the 15-degree, 0-degree, 15-degree, and 30-degree test angles and the composite force, respectively. Adduction. The mean force of adduction was also consistently greater as the position of the muscle group changed from the shortened (30 ) to lengthened ( 15 ) test angle. The difference in force recorded between these two angles was pounds. The correlation between each test angle and the composite force was again significantly high at three of the test angles. The correlation values were.889,.906,.855, and.648 between the 15- TABLE 1 degree, 0-degree, 15-degree, and 30-degree test angles and the composite force, respectively. Abduction and Adduction. The mean forces of abduction and adduction were compared at corresponding angles of muscle length. The force of abduction was greater at all four angles, but the difference was not statistically significant at any angle. Comparison of the force curves of the two muscle groups revealed that the forces were equal when the limb was at the 0-degree test angle. In this position both muscle groups were in the anatomical position. Standing Abduction and Adduction. The mean forces of abduction and adduction were compared at the 0-degree test angle. The force of abduction was greater but the difference was not statistically significant. Supine and Standing The mean forces of abduction and adduction were compared independently between the two test positions at the 0-degree test angle. The force for both muscle groups was greater in the supine position, but the difference was not statistically significant. DISCUSSION The dominant limb is commonly considered to be stronger than the nondominant one. The results of this study, in which all but two of the subjects were right dominant, showed that for hip abduction and adduction the dominant side was not always the stronger, although the difference was not significant. This corresponds with the earlier study by this investigator regarding the hip rotator muscle groups. 25 A possible explanation for these results, as pro- FORCES RECORDED (POUNDS) FOR MAXIMUM ISOMETRIC CONTRACTION OF ABDUCTOR AND ADDUCTOR MUSCLES IN TWO TEST POSITIONS AT SELECTED ANGLES IN THE RANGE OF HIP MOTION FOR TWENTY-FIVE NORMAL MEN (N 50) Test Mean Force Standard Deviation Range of Force Angles (degrees) Abduction Adduction Abduction Adduction Abduction Adduction Supine Standing Volume 48 / Number 8 849

ISOMETRIC FORCE OF HIP MUSCLES posed in the earlier study, is that an equal or greater force is required for the stabilizing action of the nondominant limb while the dominant limb is performing a

6 ISOMETRIC FORCE OF HIP MUSCLES posed in the earlier study, is that an equal or greater force is required for the stabilizing action of the nondominant limb while the dominant limb is performing a skilled movement. The consistent increase in force that accompanied both muscle groups as they changed from a shortened to a lengthened position is in agreement with the findings of Clarke 4 and Williams and Stutzman. 20 When the mean isometric forces recorded by the men in the present study were compared with those reported by Clarke, 4 it was found that the forces in the present study were considerably lower. The forces reported for men by Williams and Stutzman, 20 however, compared favorably with those in the present study. The primary disadvantage of using an apparatus such as that used in this study in a clinical setting is the amount of time required to set up and complete the testing of any given muscle group. Testing only one angle in the range of joint motion would be a great timesaver. If the "overall" strength of any given muscle group could be predicted by testing one angle in the range of joint motion, quantitative testing of patients possibly could be feasible. The choice of angle could be where the force is greatest since this information in itself is useful. Although data are not available for the hip abductor and adductor muscle groups, Williams, Tomberlin, and Robertson have demonstrated in other muscle groups that at the angle of maximum force the greatest difference in performance is evident from one age group to another. 24 Finally, knowledge of the relationship of the forces in a given range will permit the calculation of approximate forces at other angles in the range and also the composite force from testing the force at one angle. A significantly high correlation between the force at three of the test angles and the composite force was found for each muscle group in the present study. If more studies were undertaken to substantiate these high correlations, the regression equations could be used to predict the composite isometric force and the isometric force at other angles from testing just one angle in the range of joint motion. The performance computed could then be compared with data collected from normal subjects of a similar age group and anthropometrical characteristics. In the present study the difference in the force between the hip abductors and adductors was not found to be statistically significant at any of the test angles. These findings are not consistent with those reported by Clarke. 4 The difference in the stabilization provided in the two studies possibly could account for this disparity. Williams and Stutzman investigated the relationship of the agonist-antagonist muscle groups of several joints not including hip abduction and adduction. 20 They found that the strength ratio depended on the position of the joint, and at only one angle in the range were the forces equal. The forces of the two muscle groups in the present study were equal when the lower limb was in the anatomical position (0 ). The disparity between the two groups became greater as the range increased in either direction from the point of equality. The angle where the forces were equal represented a transition point on one side of which the abductor muscles were stronger in comparison with the adductors and on the other side of which the adductor muscles were the stronger group. The difference in force between the supine and standing position at 0 degrees was not found to be significant for either muscle group in this study. Again, the possibility of a test applicable to the clinic setting is apparent. Testing in the standing position requires a minimum of preparation of the apparatus, and the testing can be completed in a short period of time. The results of this study were based on tests given to a relatively small number of male subjects. As a result, conclusions should be interpreted only in reference to this study. However, the results provide an indication of what forces may be expected from the hip abductor and adductor muscles at different angles in the range of motion for the general population of males twenty to twenty-eight years of age. It would be of value to repeat the test procedure on larger samples in order to corroborate the results obtained. The establishment of norms based on age, sex, height and weight, or body-type relationships would be helpful in formulating more objective methods of evaluating patients' performance on strength tests. Some type of predictive equation might also be developed. If this type of information could supplement existing methods of evaluating muscular strength, the assessment of normal and abnormal performance of the hip abductor and adductor muscle groups would be considerably more objective and accurate. 850 PHYSICAL THERAPY

CONCLUSION Data obtained from tests of the hip abductor and adductor muscles given to twentyfive male subjects revealed the following: There was no significant statistical difference between the mean

7 CONCLUSION Data obtained from tests of the hip abductor and adductor muscles given to twentyfive male subjects revealed the following: There was no significant statistical difference between the mean forces of the dominant and nondominant abductor and adductor muscle groups. Consistently greater force was recorded for both muscle groups as they changed from a shortened to a lengthened position. There was a significantly high correlation between the force at three of the test angles and the composite force for both abduction and adduction. The "over-all" strength of either muscle group possibly could be predicted by testing one of the three angles and using the regression equations. There was no significant statistical difference between the mean forces of abduction and adduction in either test position. The forces of abduction and adduction were most nearly equal when the lower limb was in the anatomical position (0 ). There was no significant statistical difference between the mean forces at the 0-degree test angle of the two muscle groups when the two test positions were compared. REFERENCES 1. Clarke, H. H., Objective strength tests of affected muscle groups involved in orthopedic disabilities. Res. Quart., 19: , May Clarke, H. H., E. C. Elkins, G. M. Martin, and K. G. Wakim, Relationship between body position and the application of muscle power to movement of the joints. Arch. Phys. Med., 31:81-89, February Wakim, K. G., J. W. Gersten, E. C. Elkins, and G. M. Martin, Objective recording of muscle strength. Arch. Phys. Med., 31:90-99, February Clarke, H. H., and T. L. Bailey, Strength curves for fourteen joint movements. J. Phys. Ment. Rehab., 4:12-16, April-May Clarke, H. H., Improvement of objective strength tests of muscle groups by cable-tension methods. Res. Quart., 21: , December Darcus, H. D., The maximum torques developed in PHYSICAL THERAPY; pronation and supination of the right hand. J. Anat., 85:55-66, Elkins, E. C., U. M. Leden, and K. G. Wakim, Objective recording of the strength of normal muscles. Arch. Phys. Med., 32: , October Salter, N., and H. D. Darcus, The effect of the degree of elbow flexion on the maximum torques developed in pronation and supination of the right hand. J. Anat., 86: , Clarke, H. H., T. L. Bailey, and C. T. Shay, New objective strength tests of muscle groups by cabletension methods. Res. Quart., 23: , May Jarvis, D. K., Relative strength of the hip rotator muscle groups. Phys. Ther. Rev., 32: , October Winters, D., and R. Cook, The use of springs in objectively evaluating muscle strength. Phys. Ther. Rev., 32: , December Darcus, H. D., A strain gauge dynamometer for measuring the strength of muscle contraction and for re-educating muscles. Ann. Phys. Med., 1: , January Downer, A. H., Strength of the elbow flexor muscles. Phys. Ther. Rev., 33:68-70, February Kennedy, M. M., Dynamometer for measuring quadriceps femoris strength. Phys. Ther. Rev., 34: , March Clarke, H. H., Comparison of instruments for recording muscle strength. Res. Quart., 25: , December Salter, N., Methods of measurement of muscle and joint function. J. Bone Joint Surg., 37B: , August Hunsicker, P. A., Arm strength at selected degrees of elbow flexion. WADC Technical Report, , Wright Air Development Center, Beasley, W. C., Influence of method on estimates of normal knee extensor force among normal and postpolio children. Phys. Ther. Rev., 36:21-41, January Beasley, W. C., Instrumentation and equipment for quantitative clinical muscle testing. Arch. Phys. Med., 37: , October Williams, M., and L. Stutzman, Strength variation through the range of joint motion. Phys. Ther. Rev., 39: , March Tomberlin, J., Isometric force of hip rotator muscle groups. Unpublished Master's thesis, Palo Alto, California, Stanford University, June Hislop, H. J., G. R. Walters, and H. M. Hines, Electronic dynamometer for determination of human isometric strength. J. Appl. Physiol., 16: , March Beasley, W. C., Quantitative muscle testing: principles and applications to research and clinical services. Arch. Phys. Med., 42: , June Williams, M., J. Tomberlin, and K. Robertson, Muscle force curves of school children. J. Amer. Phys. Ther. Ass., 45: , June May, W. W., Maximum isometric force of the hip rotator muscle groups. J. Amer. Phys. Ther. Ass., 46: , March Volume 48 / Number 8 851

Maximal isokinetic and isometric muscle strength of major muscle groups related to age, body weight, height, and sex in 178 healthy subjects

Maximal isokinetic and isometric muscle strength of major muscle groups related to age, body weight, height, and sex in 178 healthy subjects Test protocol Muscle test procedures. Prior to each test participants