DEAN P. CURRIER, Ph.D.
The purpose of the study was to ascertain whether a wedge placed under the knee during resistive exercise enhances quadriceps strengthening and the length-tension relationship of the quadriceps. Twenty normal women students were tested for maximal isometric contraction of their left quadriceps at different knee positions. The test positions were zero, 30, 60, and 90 degrees. The greatest muscle force was recorded when the knee angle was 60 degrees and the least force was recorded when the knee extended fully. The results of the length-tension relationship of muscle obtained in this study adhered to the accepted concept. Values recorded for quadriceps force when the wedge was placed under the knee did not differ significantly from those values recorded when tht wedge was not used. The use of the wedge in quadriceps exercise does not appear to be an effective means of generating greater force than when no wedge is us :d.
A
small wedge is frequently placed under the posterior portion of the thigh adjacent to the popliteal fossa of a patient performing resistive quadriceps exercises when sitting. Review of the literature or questioning practitioners offered inconclusive reasons on the advantages of using the wedge in strength ening the quadriceps. The author has postulated that the reasons for using the wedge during resistive exercises were accepted on a subjective rather than an objective basis in clinical practice. The purpose of this study was to determine whether quadriceps force is greater when using a wedge than when not using a wedge at various positions of the knee and whether the results adhered to the lengthtension concepts of muscle.
Dr. Currier is Assistant Professor, Department of Physical Therapy, Medical College of Georgia, Au gusta, GA 30902.
870
REVIEW OF LITERATURE The length-tension relationship of the quadri ceps has been demonstrated clearly in several studies.'~ 3 Investigators agree that as the angle of the knee joint decreases during knee exten sion the muscle shortens. Williams and Stutzman showed that maximum force exerted by the quadriceps was achieved when the knee joint was flexed between 50 and 70 degrees, and minimum force was recorded when the knee was fully extended (zero degrees). 3 Several authors have mentioned using a wedge 4-9 made from towel rolls, cushion, 6 folded blanket, 5 rubber padding, 8,9 sandbag, 7 or commercially constructed wedges, but none has tested the effect of the wedge in quadriceps strengthening. DeLorme and others have sug gested that the knee be elevated so that the femur will be parallel to the floor when the knee is extended fully. 4 - 8 A small rubber PHYSICAL THERAPY
Downloaded from https://academic.oup.com/ptj/article-abstract/55/8/870/4567833 by University of Texas at Dallas user on 17 February 2019
Evaluation of the Use of a Wedge in Quadriceps Strengthening
METHOD AND MATERIAL
Twenty normal women students ranging in age from twenty to twenty-three years (mean = 21.3 years) were tested for maximal isometric contraction of the left quadriceps at knee positions of zero, 30, 60, and 90 degrees. Each knee angle was measured with a goniometer. The subject was seated on an N-K table* with the hip angle varying between 80 and 100 degrees and with the arms extended and the hands grasping the sides of the table. The test position simulated the actual sitting postures of patients during exercise. The subject's right knee was flexed and permitted to hang freely over the front edge of the table. The left leg was attached to a ring-type cable tensiometer* by an ankle cuff. The other end of the tensiometer was attached to a series of eyebolts by means of a nonelastic nylon cord. The eyebolts were located in a series (2.5 cm apart) along an H-shaped metal frame which was placed under the legs of the table and anchored securely by the subject's body weight. The series of eyebolts made it possible to maintain a right angle position, thus enabling the examiner to test the quadriceps force at the desired knee positions. The subject's foot was held in the desired test position by the examiner until the subject was encouraged verbally to exert maxi mal isometric contraction of the left quadriceps for a period of five seconds. Holding the foot in position prevented muscle fatigue and elimi nated undesired momentum before the iso metric contraction. A stopwatch was used to determine the duration of muscle contractions. * NK Products Co., Inc., Santa Cruz, CA 9 5 0 6 1 .
Volume 55 / Number 8, August 1975
TABLE
Mean, Standard Deviation, and Range of Maximal Isometric Force of Quadriceps with and without a Wedge (N=20) Angle (degrees) 90 With Without 60 With Without 30 With Without 0 With Without
Mean (kg)
S.D. (kg)
Range (kg)
18.52 18.50
2.16 4.62
8.18-29.55 10.00-25.45
18.57 19.36
6.61 6.02
8.18-31.82 7.73-31.82
15.23 14.11
4.84 5.39
8.64-24.55 6.36-23.64
8.14 6.66
3.23 3.09
2.73-12.73 2.73-13.64
At least one minute of rest was provided between contractions while the examiner pre pared for the next test condition. The test condition consisted of a specific angle with and without the wedge being used, and each angle for each subject was determined randomly. Each subject was tested at each angle with and without the wedge, and each con tracted the quadriceps maximally for a total of eight repetitions. Subjects were discouraged from lifting their trunks or rotating their hips during the test. The values achieved on the tensiometer were recorded for later calcula tions. The wedge was a quadriceps rest constructed of a block of wood fourteen by sixteen by two centimeters, topped with compressible rubber (compressible from 5.5 to 5.0 cm) and covered with leatherette. RESULTS
The descriptive statistics of the maximum isometric force recorded for the quadriceps with and without the use of a wedge are shown in the Table. The greatest force was recorded when the knee was positioned at 60 degrees and the least force was recorded at the zero-degree position. The mean forces were rather con sistent for a particular position of the knee when using and not using the wedge and are reflected by their standard deviations and ranges. 871
Downloaded from https://academic.oup.com/ptj/article-abstract/55/8/870/4567833 by University of Texas at Dallas user on 17 February 2019
padding under the knee has been suggested for protecting the patient against pain 8,9 and pressure 8 in the distal posterior portion of the thigh during quadriceps exertion. When queried, physical therapists who favored the use of the wedge have implied that the wedge increases the mechanical advantage of the quadriceps when the femur is maintained in a position parallel to the surface of the exercise unit. The contention is that the parallel position of the femur permits greater force to be exerted by the quadriceps and, therefore, enhances quadriceps strengthening.
DISCUSSION
WITH WEDGE
WITHOUT WEDGE
0
30
60
90
KNEE EXTENSION (DEGREES)
Fig. 1. Relationship of knee position to mean maximal force exerted by quadriceps.
The data were treated by a factorial analysis of variance design with repetition of measure ment over each factor. No significant difference was found for quadriceps exertion at the same angle whether or not the wedge was used. A significant F ratio was obtained for the forces recorded when the angle of the knee joint was varied. Newman Keuls's method of post hoc analysis showed that the force attained at the 90- and 60-degree positions did not differ significantly, but were significantly greater than that attained at the 30- and zero-degree positions when the wedge was used. In addi tion, the force attained at the 30-degree position was significantly greater than the force at the zero-degree position when the wedge was used. Similar relationships of angles of the knee joint to mean isometric force were obtained whether the wedge was or was not used. There was no significant difference in individual comparisons of the subjects and muscle length interaction nor of the subjects and muscle force interaction. All F ratios and means were tested at the 0.01 level of significance. 872
PHYSICAL THERAPY
Downloaded from https://academic.oup.com/ptj/article-abstract/55/8/870/4567833 by University of Texas at Dallas user on 17 February 2019
„ 12
The results of the length-tension relationship of muscle obtained in this study are in agreement with others. 1-3 ' 10 The greatest forces were recorded over the range of 60 to 90 degrees with the 60-degree position being the position where the greatest single force was recorded. Figure 1 shows clearly that the resting length of the quadriceps for the subjects tested in this study was at the 60-degree position of the knee. The resting length is defined by physiologists as the length at which a muscle develops its maximal active force. 11 Also, from a mechanical point of view, the perpendicular of the force resultant in the quadriceps tendon from the variable axis formed by the change of knee position is less at zero degrees and greater at the other posi tions. 10 The smaller distance of the force resultant when the knee is extended places the quadriceps at a disadvantage when maximum shortening occurs, 12 and accounts for the diminished force recorded. Figure 1 and the Table show the mean values recorded for quadriceps force when the wedge was used under the knee to be slightly greater at the zero-, 30-, and 90-degree positions than when the wedge was not used. Since the differences in the mean values recorded for quadriceps force were not statistically different, the differences between the means are sampling fluctuations and cannot be interpreted as being favorable towards the use of a wedge. The wedge does not appear to change the distance of the force resultant at the knee. DeLorme and others have suggested that the exercised knee be elevated five to eight centi meters so that the femur will be parallel to the floor when the knee is extended fully. 4 ' 8 In this study, the wedge maintained the femur parallel to the floor when the knee was extended fully, and when the wedge was not used the femur sloped slightly toward the floor. The knee joint was extended fully in the zero-degree position, however, whether the wedge was used or not used. Gravity acted fully on the leg being tested only when the wedge was used. When the wedge was not used, the leg being tested was subjected to less than the full force of gravity. Recognition of the effects of gravity may have led to the incorrect reasoning
Volume 55 / Number 8, A ugust 1975
LEG POSITIONS WITH WEDGE WITHOUT WEDGE
0-DEGREE POSITIONS
J
18,0 KGM. LOAD
0= 6.6 DEGREES Fig. 2. Knee extended fully with and without a wedge during quadriceps strengthening. Note slight change in position of leg. causes increased pressure at the posterior-distal thigh during quadriceps strengthening exercises. Several of the subjects tested commented on the increased pressure behind their knees when the wedge was used. CONCLUSION
Results of this study show from a physio logic and trigonometric point of view that a wedge of the size used commonly by physical therapists could not be advantageous for quad riceps strengthening. Also, deduction from a principle of physics has enabled the author to conclude that the wedge causes increased pressure to the posterior-distal thigh during quadriceps strengthening exercises and may add to the subject's discomfort. The use of a wedge placed under a subject's knee during quadriceps strengthening has little value and its use may simply be a matter of therapist preference. Acknowledgment: The author wishes to express his appreciation to the senior physical therapy students for their invaluable assistance in accumulating data for this study. 873
Downloaded from https://academic.oup.com/ptj/article-abstract/55/8/870/4567833 by University of Texas at Dallas user on 17 February 2019
that use of the wedge causes the quadriceps to exert more force when contracting against a known resistance than when a wedge is not used. In the present study, the mean force recorded for the quadriceps was slightly greater in three of the four knee positions when the wedge was used than when the wedge was not used (Fig. 1); however, these differences in force were not statistically significant. Since the knee joint is extended fully in the zero-degree position with or without the wedge, the wedge must act on the hip joint by elevating the thigh (Fig. 2). When the thigh is not elevated by a wedge, the full force of gravity is reduced. According to trigonometric functions, when the angle of a joint is in the zero-degree position, the sine of the angle between a zero-degree joint position and a 90-degree angle of force application is l.O. 1 3 In such a situation the full force of the resistance is received by the muscle acting against the resistance. For example, if a wedge five centimeters high is placed beneath the knee forty centimeters from the hip joint (assume zero-degree position of knee for this example) and a force of eighteen kilograms is offered as resistance (90-degree angle of force application) to the quadriceps, the full eighteen kilograms will be translated to the quadriceps because the femur will be parallel to the floor (18 kg x sine 1.0 = 18.0 kg). If the wedge is removed from underneath the knee, the femur will slope slightly towards the floor when resting on top of the exercise table. In the example, the difference in the angle formed at the hip when the wedge is removed is 6.6 degrees of extension from the angle formed when the wedge is used to maintain the femur parallel to the floor. In trigonometric function, a change in joint position of 6.6 degrees takes a sine value of 0.99272 and when applied to the reduced force of gravity the quadriceps would then be lifting 17.86896 kilograms (Fig. 2). This small reduction in load may account for the slight differences in mean quadriceps forces recorded in this study. Placement of a wedge or any material under the knee will reduce contact of the exercise table's surface with the posterior surface of the distal thigh. Since pressure is proportional to mass and inversely proportional to area, the wedge reduces the area of leg contact and
REFERENCES 8. Schenck JM, Forward EM: Quantitative strength changes with test repetitions. Phys Ther 45:562-569, 1965 9. McGown HL: Effects of cold application on maximal isometric contraction. Phys Ther 47:185-192, 1967 10. Haffajee D, Moritz U, Svantesson G: Isometric knee extension strength as a function of joint angle, muscle length and motor unit activity. Acta Orthop Scand 43:138-147, 1972 11. Lehmkuhl D: Local factors in muscle perform ance. Phys Ther 46:473-484, 1966 12. Hallen LG, Lindahl O: Muscle function in knee extension. Acta Orthop Scand 38:434-444, 1967 13. Williams M, Lissner HR: Biomechanics of Human Motion. Philadelphia, W.B. Saunders Company, 1962, pp 79-81
Chest Disorders in Children A monograph based on proceedings of a symposium on Chest Dis orders in Children, held at Boston University, and sponsored by the Departments of Occupational and Physical Therapy, Sargent College of Allied Health Professions of Boston University and Physical Therapy, Journal of the American Physical Therapy Association. Articles in the monograph have appeared in the Journal. Edited by Helen J. Hislop, Ph.D., and Joan Sanger Paper, 163 pp, illus, $2.25
Order from:
American Physical Therapy Association 1156 15th St., N.W.. Washington, D.C. 20005
874
PHYSICAL THERAPY
Downloaded from https://academic.oup.com/ptj/article-abstract/55/8/870/4567833 by University of Texas at Dallas user on 17 February 2019
1. Clarke HH, Bailey T: Strength curves for fourteen joint measurements. J Assoc Phys Ment Rehabil 4:12-16, 1950 2. Clarke H, Elkins EC, Martin GM, et al: Relation ship between body position and the application of muscle power to movements of the joints. Arch Phys Med 31:81-89, 1950 3. Williams M, Stutzman L: Strength variation through the range of joint motion. Phys Ther Rev 39:145-152, 1959 4. DeLorme TL: Restoration of muscle power by heavy resistance exercises. J Bone Joint Surg 27A: 645-667, 1945 5. DeLorme TL: Heavy resistance exercises. Arch Phys Med 27:607-630, 1946 6. Allis JB: Smillie board: A quadriceps exerciser. Phys Ther Rev 35:374-377, 1955 7. Schwied D, Vignos PJ, Archibald KC: Effects of brief maximum exercise on quadriceps strength in children. Am J Phys Med 41:189-197, 1962
The purpose of the study was to ascertain whether a wedge placed under the knee during resistive exercise enhances quadriceps strengthening and the length-tension relationship of the quadriceps. Twenty normal women students were tested for maximal isometric contraction of their left quadriceps at different knee positions. The test positions were zero, 30, 60, and 90 degrees. The greatest muscle force was recorded when the knee angle was 60 degrees and the least force was recorded when the knee extended fully. The results of the length-tension relationship of muscle obtained in this study adhered to the accepted concept. Values recorded for quadriceps force when the wedge was placed under the knee did not differ significantly from those values recorded when tht wedge was not used. The use of the wedge in quadriceps exercise does not appear to be an effective means of generating greater force than when no wedge is us :d.
A
small wedge is frequently placed under the posterior portion of the thigh adjacent to the popliteal fossa of a patient performing resistive quadriceps exercises when sitting. Review of the literature or questioning practitioners offered inconclusive reasons on the advantages of using the wedge in strength ening the quadriceps. The author has postulated that the reasons for using the wedge during resistive exercises were accepted on a subjective rather than an objective basis in clinical practice. The purpose of this study was to determine whether quadriceps force is greater when using a wedge than when not using a wedge at various positions of the knee and whether the results adhered to the lengthtension concepts of muscle.
Dr. Currier is Assistant Professor, Department of Physical Therapy, Medical College of Georgia, Au gusta, GA 30902.
870
REVIEW OF LITERATURE The length-tension relationship of the quadri ceps has been demonstrated clearly in several studies.'~ 3 Investigators agree that as the angle of the knee joint decreases during knee exten sion the muscle shortens. Williams and Stutzman showed that maximum force exerted by the quadriceps was achieved when the knee joint was flexed between 50 and 70 degrees, and minimum force was recorded when the knee was fully extended (zero degrees). 3 Several authors have mentioned using a wedge 4-9 made from towel rolls, cushion, 6 folded blanket, 5 rubber padding, 8,9 sandbag, 7 or commercially constructed wedges, but none has tested the effect of the wedge in quadriceps strengthening. DeLorme and others have sug gested that the knee be elevated so that the femur will be parallel to the floor when the knee is extended fully. 4 - 8 A small rubber PHYSICAL THERAPY
Downloaded from https://academic.oup.com/ptj/article-abstract/55/8/870/4567833 by University of Texas at Dallas user on 17 February 2019
Evaluation of the Use of a Wedge in Quadriceps Strengthening
METHOD AND MATERIAL
Twenty normal women students ranging in age from twenty to twenty-three years (mean = 21.3 years) were tested for maximal isometric contraction of the left quadriceps at knee positions of zero, 30, 60, and 90 degrees. Each knee angle was measured with a goniometer. The subject was seated on an N-K table* with the hip angle varying between 80 and 100 degrees and with the arms extended and the hands grasping the sides of the table. The test position simulated the actual sitting postures of patients during exercise. The subject's right knee was flexed and permitted to hang freely over the front edge of the table. The left leg was attached to a ring-type cable tensiometer* by an ankle cuff. The other end of the tensiometer was attached to a series of eyebolts by means of a nonelastic nylon cord. The eyebolts were located in a series (2.5 cm apart) along an H-shaped metal frame which was placed under the legs of the table and anchored securely by the subject's body weight. The series of eyebolts made it possible to maintain a right angle position, thus enabling the examiner to test the quadriceps force at the desired knee positions. The subject's foot was held in the desired test position by the examiner until the subject was encouraged verbally to exert maxi mal isometric contraction of the left quadriceps for a period of five seconds. Holding the foot in position prevented muscle fatigue and elimi nated undesired momentum before the iso metric contraction. A stopwatch was used to determine the duration of muscle contractions. * NK Products Co., Inc., Santa Cruz, CA 9 5 0 6 1 .
Volume 55 / Number 8, August 1975
TABLE
Mean, Standard Deviation, and Range of Maximal Isometric Force of Quadriceps with and without a Wedge (N=20) Angle (degrees) 90 With Without 60 With Without 30 With Without 0 With Without
Mean (kg)
S.D. (kg)
Range (kg)
18.52 18.50
2.16 4.62
8.18-29.55 10.00-25.45
18.57 19.36
6.61 6.02
8.18-31.82 7.73-31.82
15.23 14.11
4.84 5.39
8.64-24.55 6.36-23.64
8.14 6.66
3.23 3.09
2.73-12.73 2.73-13.64
At least one minute of rest was provided between contractions while the examiner pre pared for the next test condition. The test condition consisted of a specific angle with and without the wedge being used, and each angle for each subject was determined randomly. Each subject was tested at each angle with and without the wedge, and each con tracted the quadriceps maximally for a total of eight repetitions. Subjects were discouraged from lifting their trunks or rotating their hips during the test. The values achieved on the tensiometer were recorded for later calcula tions. The wedge was a quadriceps rest constructed of a block of wood fourteen by sixteen by two centimeters, topped with compressible rubber (compressible from 5.5 to 5.0 cm) and covered with leatherette. RESULTS
The descriptive statistics of the maximum isometric force recorded for the quadriceps with and without the use of a wedge are shown in the Table. The greatest force was recorded when the knee was positioned at 60 degrees and the least force was recorded at the zero-degree position. The mean forces were rather con sistent for a particular position of the knee when using and not using the wedge and are reflected by their standard deviations and ranges. 871
Downloaded from https://academic.oup.com/ptj/article-abstract/55/8/870/4567833 by University of Texas at Dallas user on 17 February 2019
padding under the knee has been suggested for protecting the patient against pain 8,9 and pressure 8 in the distal posterior portion of the thigh during quadriceps exertion. When queried, physical therapists who favored the use of the wedge have implied that the wedge increases the mechanical advantage of the quadriceps when the femur is maintained in a position parallel to the surface of the exercise unit. The contention is that the parallel position of the femur permits greater force to be exerted by the quadriceps and, therefore, enhances quadriceps strengthening.
DISCUSSION
WITH WEDGE
WITHOUT WEDGE
0
30
60
90
KNEE EXTENSION (DEGREES)
Fig. 1. Relationship of knee position to mean maximal force exerted by quadriceps.
The data were treated by a factorial analysis of variance design with repetition of measure ment over each factor. No significant difference was found for quadriceps exertion at the same angle whether or not the wedge was used. A significant F ratio was obtained for the forces recorded when the angle of the knee joint was varied. Newman Keuls's method of post hoc analysis showed that the force attained at the 90- and 60-degree positions did not differ significantly, but were significantly greater than that attained at the 30- and zero-degree positions when the wedge was used. In addi tion, the force attained at the 30-degree position was significantly greater than the force at the zero-degree position when the wedge was used. Similar relationships of angles of the knee joint to mean isometric force were obtained whether the wedge was or was not used. There was no significant difference in individual comparisons of the subjects and muscle length interaction nor of the subjects and muscle force interaction. All F ratios and means were tested at the 0.01 level of significance. 872
PHYSICAL THERAPY
Downloaded from https://academic.oup.com/ptj/article-abstract/55/8/870/4567833 by University of Texas at Dallas user on 17 February 2019
„ 12
The results of the length-tension relationship of muscle obtained in this study are in agreement with others. 1-3 ' 10 The greatest forces were recorded over the range of 60 to 90 degrees with the 60-degree position being the position where the greatest single force was recorded. Figure 1 shows clearly that the resting length of the quadriceps for the subjects tested in this study was at the 60-degree position of the knee. The resting length is defined by physiologists as the length at which a muscle develops its maximal active force. 11 Also, from a mechanical point of view, the perpendicular of the force resultant in the quadriceps tendon from the variable axis formed by the change of knee position is less at zero degrees and greater at the other posi tions. 10 The smaller distance of the force resultant when the knee is extended places the quadriceps at a disadvantage when maximum shortening occurs, 12 and accounts for the diminished force recorded. Figure 1 and the Table show the mean values recorded for quadriceps force when the wedge was used under the knee to be slightly greater at the zero-, 30-, and 90-degree positions than when the wedge was not used. Since the differences in the mean values recorded for quadriceps force were not statistically different, the differences between the means are sampling fluctuations and cannot be interpreted as being favorable towards the use of a wedge. The wedge does not appear to change the distance of the force resultant at the knee. DeLorme and others have suggested that the exercised knee be elevated five to eight centi meters so that the femur will be parallel to the floor when the knee is extended fully. 4 ' 8 In this study, the wedge maintained the femur parallel to the floor when the knee was extended fully, and when the wedge was not used the femur sloped slightly toward the floor. The knee joint was extended fully in the zero-degree position, however, whether the wedge was used or not used. Gravity acted fully on the leg being tested only when the wedge was used. When the wedge was not used, the leg being tested was subjected to less than the full force of gravity. Recognition of the effects of gravity may have led to the incorrect reasoning
Volume 55 / Number 8, A ugust 1975
LEG POSITIONS WITH WEDGE WITHOUT WEDGE
0-DEGREE POSITIONS
J
18,0 KGM. LOAD
0= 6.6 DEGREES Fig. 2. Knee extended fully with and without a wedge during quadriceps strengthening. Note slight change in position of leg. causes increased pressure at the posterior-distal thigh during quadriceps strengthening exercises. Several of the subjects tested commented on the increased pressure behind their knees when the wedge was used. CONCLUSION
Results of this study show from a physio logic and trigonometric point of view that a wedge of the size used commonly by physical therapists could not be advantageous for quad riceps strengthening. Also, deduction from a principle of physics has enabled the author to conclude that the wedge causes increased pressure to the posterior-distal thigh during quadriceps strengthening exercises and may add to the subject's discomfort. The use of a wedge placed under a subject's knee during quadriceps strengthening has little value and its use may simply be a matter of therapist preference. Acknowledgment: The author wishes to express his appreciation to the senior physical therapy students for their invaluable assistance in accumulating data for this study. 873
Downloaded from https://academic.oup.com/ptj/article-abstract/55/8/870/4567833 by University of Texas at Dallas user on 17 February 2019
that use of the wedge causes the quadriceps to exert more force when contracting against a known resistance than when a wedge is not used. In the present study, the mean force recorded for the quadriceps was slightly greater in three of the four knee positions when the wedge was used than when the wedge was not used (Fig. 1); however, these differences in force were not statistically significant. Since the knee joint is extended fully in the zero-degree position with or without the wedge, the wedge must act on the hip joint by elevating the thigh (Fig. 2). When the thigh is not elevated by a wedge, the full force of gravity is reduced. According to trigonometric functions, when the angle of a joint is in the zero-degree position, the sine of the angle between a zero-degree joint position and a 90-degree angle of force application is l.O. 1 3 In such a situation the full force of the resistance is received by the muscle acting against the resistance. For example, if a wedge five centimeters high is placed beneath the knee forty centimeters from the hip joint (assume zero-degree position of knee for this example) and a force of eighteen kilograms is offered as resistance (90-degree angle of force application) to the quadriceps, the full eighteen kilograms will be translated to the quadriceps because the femur will be parallel to the floor (18 kg x sine 1.0 = 18.0 kg). If the wedge is removed from underneath the knee, the femur will slope slightly towards the floor when resting on top of the exercise table. In the example, the difference in the angle formed at the hip when the wedge is removed is 6.6 degrees of extension from the angle formed when the wedge is used to maintain the femur parallel to the floor. In trigonometric function, a change in joint position of 6.6 degrees takes a sine value of 0.99272 and when applied to the reduced force of gravity the quadriceps would then be lifting 17.86896 kilograms (Fig. 2). This small reduction in load may account for the slight differences in mean quadriceps forces recorded in this study. Placement of a wedge or any material under the knee will reduce contact of the exercise table's surface with the posterior surface of the distal thigh. Since pressure is proportional to mass and inversely proportional to area, the wedge reduces the area of leg contact and
REFERENCES 8. Schenck JM, Forward EM: Quantitative strength changes with test repetitions. Phys Ther 45:562-569, 1965 9. McGown HL: Effects of cold application on maximal isometric contraction. Phys Ther 47:185-192, 1967 10. Haffajee D, Moritz U, Svantesson G: Isometric knee extension strength as a function of joint angle, muscle length and motor unit activity. Acta Orthop Scand 43:138-147, 1972 11. Lehmkuhl D: Local factors in muscle perform ance. Phys Ther 46:473-484, 1966 12. Hallen LG, Lindahl O: Muscle function in knee extension. Acta Orthop Scand 38:434-444, 1967 13. Williams M, Lissner HR: Biomechanics of Human Motion. Philadelphia, W.B. Saunders Company, 1962, pp 79-81
Chest Disorders in Children A monograph based on proceedings of a symposium on Chest Dis orders in Children, held at Boston University, and sponsored by the Departments of Occupational and Physical Therapy, Sargent College of Allied Health Professions of Boston University and Physical Therapy, Journal of the American Physical Therapy Association. Articles in the monograph have appeared in the Journal. Edited by Helen J. Hislop, Ph.D., and Joan Sanger Paper, 163 pp, illus, $2.25
Order from:
American Physical Therapy Association 1156 15th St., N.W.. Washington, D.C. 20005
874
PHYSICAL THERAPY
Downloaded from https://academic.oup.com/ptj/article-abstract/55/8/870/4567833 by University of Texas at Dallas user on 17 February 2019
1. Clarke HH, Bailey T: Strength curves for fourteen joint measurements. J Assoc Phys Ment Rehabil 4:12-16, 1950 2. Clarke H, Elkins EC, Martin GM, et al: Relation ship between body position and the application of muscle power to movements of the joints. Arch Phys Med 31:81-89, 1950 3. Williams M, Stutzman L: Strength variation through the range of joint motion. Phys Ther Rev 39:145-152, 1959 4. DeLorme TL: Restoration of muscle power by heavy resistance exercises. J Bone Joint Surg 27A: 645-667, 1945 5. DeLorme TL: Heavy resistance exercises. Arch Phys Med 27:607-630, 1946 6. Allis JB: Smillie board: A quadriceps exerciser. Phys Ther Rev 35:374-377, 1955 7. Schwied D, Vignos PJ, Archibald KC: Effects of brief maximum exercise on quadriceps strength in children. Am J Phys Med 41:189-197, 1962
