jOUKNAL
A PPLIkm August
OF
Vol. 25, No. 2,
PHYsroLoGY
1968.
Strength extensors
f’rinltd
in U.S.A.
of forearm flexors and in men and women M0HAN SINGH AND PETER V. KARPOVICH Physiological Research Laboratory, Sprinplfield College, Sjningfield, Massachusetts
SINGH, armjexors 177-180. tensors of by means
MOHAN, AND PETER V. KARPOVICH. Strength ufforeand extensors in men and women. J. Appl. Physiol. 25(2) : 1968.-The strength of the elbow flexors and exboth arms was measured in 12 men and 1.1 women of an electric dynamometer. The results showed that,
they could exert maximum force when under minimal or near minimal length. Doss and Karpovich (3) found that the maximum eccentric strength of forearm flexors was 39.7 % greater than their concentric strength. Sing-h and Karpovich (7) reported that the maximum eccentric strength of preferred forearm flexors was 32.7 % and of extensors was 14.2 70 greater than their respective concentric strength. They also found the maximum isometric strength of forearm flexors to be 41.6% greater than that of extensors. However, the eccentric strength of extensors at 140” was significantly less than their isometric and concentric strengths.
with
the exception of two conditions in men, there was no significant difference in strength between the preferred and the nonpreferred arm. The exceptions were: isometric contraction of flexors at 50” and concentric contraction the preferred arm was of extensors at 90’. In both instances stronger. The average strength of extensors expressed in percent of flexors’ strength in men varied from 53-55 for concentric, 47-48 for eccentric, and 52-57 for isometric contractions. In women it was 61-68 for concentric, 49-51 for eccentric, and 57-60 for isometric contractions. Expressed in percent of men’s strength, the means of all tests for women were between 42-47 with one exception: the concentric strength of the flexors in the preferred arm, which ranged between 35-39. statistically
strength
and
sex;
MATERIALS
AND
METHODS
The special dynamometer used in this study was the same as described elsewhere (7), except that the back rest and yokes for stabilization of shoulders were not used. The dynamometer consisted of a reversible electric motor with a gear reduction (11600) box and a lever arm attached to its output shaft, A strain gauge was built into the lever arm, and the muscular force was measured in foot pounds of torque. An electrogoniometer was attached to the axis of rotation of the lever arm and it continuously recorded the angle of rotation between 50 and 140”. For testing, the subject placed his elbow on’ the elbow rest and applied his force to the wrist yoke placed just proximally to the wrist joint. The yoke was placed either above or under the wrist, depending on whether flexors or extensors were being tested. In testing eccentric? force, the subject resisted the movement of the lever; in testing concentric contractions, he assisted that movement. In both instances, the subject exerted maximum force upon the wrist yoke. In order to test the left arm, the subject reversed his position and the lever arm was rotated 180’ so that he could place his left elbow on the elbow rest platform and use the wrist yoke. During all the tests in this study the wrist was always in midposition. Each subject was given a set of 20 tests for flexors and extensors of both arms in one session, which
muscle
A
LTHOUGH MANY STUDIES have been made regarding the maximum strength of forearm flexors and extensors (l-7), no research so far has been carried out to measure and compare the maximum isotonic strength of the preferred and nonpreferred forearm flexors and extensors and to make comparison in and between the sexes. For these reasons the present study was undertaken. Clarke (1) measured the isometric strength of forearm flexors and extensors in men. He found that the strength of forearm flexors at the elbow angles of 115 and of 40” was 74 and 51 lb., respectively. Clarke et al. (Z), in another study, determined the strength of forearm flexors and extensors at nine different angles. They found that forearm extensors had maximum strength from 80 to 140”. Elkins et al. (4) studied the maximum isometric strength of forearm flexors and extensors in men and women. They found a gradual increase in strength of flexors as the forearm was extended, with the peak at 120”. They also concluded that the extensors of the forearm were considerably weaker than the flexors, and that
l In eccentric shortens. 177
contraction
the muscle
lengthens;
in concentric
it
178
M.
lasted for about 1 hr. The set consisted of 20 tests: four concentric, four eccentric, and isometric tests at 50, 90, and 130” repeated four times.
RESULTS
AND
in good personal
DISCUSSION
Table 2 shows maximum concentric, eccentric, and isometric torques of preferred and nonpreferred forearm flexors and extensors in men tested between 50 and 140” of the elbow angle. The t ratios for the significance of the difference between the means of these torques for preferred and nonpreferred arms were calculated but not reported in this article because all of them, except two, were not statistically significant. The two exceptions were isometric contraction of flexors at 50”, t ratio being 2.93, and concentric contraction of extensors at 90”, f being 2.2 1, both in favor of the preferred arm (the minimum f, significant at 0.05 level, was 2.20). From Table 2, it may also be seen that means for the men’s strength of the extensors expressed in percent of TAB
LE 1. Subjects’ personal data 12 1Men
Forearm length, inches* Age, years Height, inches Weight, lb. * From TABLE
the lateral
11 Women
Range
Mean
Range
Mean
9.5-11.5
10.3
9-10
9.2
18-35 66-72 146-200
24,6 69.3 165.9
epicondyle
to styioid
Concentric
25.3 65.4 130.9
process.
2. Strength of elbow extensors and flexors Preferred
Elbow Angle,”
22-29 62-68.8 115-160
Nonpref
Eccentric E
F
Isometric
Concentric
28 29 30 30 30 27 23 21 20 18
46 49 55 59 60 59 57 55 53 51
F
E%
31 34 37 39 41 42 43 43 42 39
58 65 65 62 59 55 49 47 43 44
61 59 55 51 50 46 40 38 38 35
Mean Range G
Eccentric
26
58
52
40
47 17-24 = extensors,
43-65 r
= flexors,
18-30 EyO
t 46-60 -
35-61
= strength
58
17 20 22 22 21 21 20 19 18 16
E%
E
F
E%
E
F
E%
29 31 35 37 38 40 42 43 42 39
59 65 63 59 55 53 48 44 43 41
26 27 28 30 30 28 26 23 20 17
41 48 53 57 59 58 55 54 55 50
63 56 53 53 51 48 47 43 36 34
27
40
68
31
51
61
21
49
43
52 ZO-3C
45-52
40-58
53 16-22
29-43
41-65
48 1 -
of E as percent
of F.
Isometric
.----
F
--
18 22 24 24 24 23 21 20 18 17
KARPOVICH
erred Arm
_-
E%
P. V.
(in ft-lb. of torque) in 12 men
Arm
-E
50 60 70 80 90 100 110 320 130 140
AND
flexors’ strength of preferred and nonpreferred arms were, respectively, 53-55 during concentric contraction, 47-48 during eccentric contractions, and 52-57 during isometric contractions. However, the percentage varied considerably at different angles. For instance, during eccentric contractions of nonpreferred arm the range was 34-63 %. This variation is understandable, because it depends on the relative muscle length. At acute angles of the elbow extensors are longer and stronger than at obtuse angles, while the reverse is true for the flexors. For this reason the ratio of extensors’ strength to that of flexors’ decreases with an increase in degrees of the elbow angle. From the data given in Table 2 curves were plotted (not included in this article). The general shape of all of them, except one, was the same as published previously (7). The exception was the curve of the eccentric force of the extensors. For the preferred arm, instead of becoming less than the isometric force at 100” and less than concentric at 125”, it became equal to isometric strength at 90” but remained greater than concentric strength at a11 points, although coming very close at 1 lo”, the difference being only 2 ft-lb. For the nonpreferred arm, the isometric strength was greater by 1 ft-lb. than eccentric strength at all points. One possible explanation of this may be that in the previous investigation (7) the forearm was in supine position and not in midposition as in the present study. The concentric strength curve was below the eccentric one; however, at 140” it was only 1 ft-lb. below. Analysis of the data obtained on women revealed that there was no statistically significant difference in the strength of preferred and nonpreferred arms. Instead of presenting data in a tabular form, Fig. 1 is given here. It shows four curves representing eccentric and concentric strengths of the elbow flexors and extensors for the preferred arm. The isometric strength is indicated at 50, 90, and 130” by open circles. As far as the investigators
SUBJECTS
College students, 12 men and 11 women, physical health, were used as subjects. Their data are given in Table 1.
SINGH
41-59
34-63
57 21-31
40-5 1 43-68
SEX
AND
STRENGTH
OF
ELBOW
FLEXORS
AND
179
EXTENSORS
know, this is the first time that the curves of maximum isotonic strength in women have ever been presented. No curves for the strength of the nonpreferred arm are given because they are substantially the same as of the preferred arm. It may be seen that, for the flexors, eccentric strength was always greater than the concentric. (For the nonpreferred arm, isometric force remained below that of eccentric at all points.) For the extensors, the eccentric force at all points was above the concentric. (The same is true for the nonpreferred arm.) The isometric force, for all practical purposes, was equal to the eccentric (& 1 ft-lb.). Table 3 gives the strength of women’s extensors expressed as percent of flexors’ strength. The means for nonpreferred and preferred arms were 61 and 68 % during concentric contractions, 49 and 51 % during eccentric contractions, and 60 and 57 7~ during isometric contractions. As in men, there was also a considerable deviation 3or
TABLE 4. Strength of elbow extensors and j?exors in II women expressed in percent of men? strength* Extensors EIbow Angle,”
Preferred
arm
Flexors Nonpreferred arm
Con
Ecc
Iso
Con
Ecc
52 44 42 48 47 47 45 44 47 42
44 44 45 46 45 47 49 48 51 50
42
50 48 47 48 53 49 50 47 43 46
41 43 48 44 48 48 49 48 48 49
Mean
46
47
47
48
47
Range
*252
M51
4252
*353
#l49
50 60 70 80 90 100 110 120 130 140
48
52
Preferred Is0
46
46
con
Ecc
xso
Con
Ecc --
Iso
37 39 38 37 37 36 35 35 37 38
43 46 43 42 43 42 42 41 41 42
47
46 45 43 44 43 42 40 37 37 38
51 50 50 48 45 45 46 46 42 44
46
43
43
42
47
43
fl46
3947
3746
2251
3946
37 3946
arm
3539
L
42
39
I
44
39
-
Con = concentric, Ecc = eccentric, * The latter was assumed to be 100%.
L
ELBOW
----
ANGLE I I
l
50
60
70
80
90
IN I
100
I
DEGREES 1 1 120 t30
II0
1
140
FIG. 1. Maximum torques of the elbow flexors, 1, and extensors 2, of the preferred arm in 11 women. E = eccentric, I = isometric, and C = concentric contractions.
TABLE 3. Strength of tdbow extenSOrS expressed as percent of flexors’ strength in II women Preferred
Elbow Angle,” Con
Ecc
75 77 71 86 73 73 60 60 50 47
Mean Range
50 60 70 80 90 100 110 120 130 140
Con
=
Arm
Nonpreferred
Arm
Is0
Con
Ecc
Is0
60 57 58 56 50 48 46 43 45 43
52
62 71 67 69 69 59 59 56 53 47
52 50 50 48 52 54 52 44 43 40
61
68
51
57
61
60
47-86
43-60
52-64
47-7 1
53-64
concentric,
Ecc
+
64
53
=
eccentric,
ho
= Isometrxc.
64
53
Iso
=
isometric.
from a mean. For instance, for concentric contractions of the preferred arm the range was 47-86 %. Table 4 gives women’s strength expressed in percent of men’s strength. The means for all tests, except one, ran between 42 and 47 %. The average for all the isotonic tests was 44.6 % and for isometric 44 %. The exception was the strength of the preferred arm during concentric contraction of the flexors, for which the mean was 37 %. This is much lower than the percent for a similar contraction in the nonpreferred arm. Inquiries among female subjects and nonsubjects regarding the use of the preferred arm, especially in carrying heavy objects, gave no information of value, An obvious explanation may be that men use the flexors of the preferred arm much more and with disproportionately greater force than women. It may be added that in our culture the man still protects the woman from carrying heavy loads. It may be of interest to compare the strength of the flexors in the preferred arm in cultures where the woman is still a beast of burden. Incidentally, Hettinger (5) reported that the strength of the forearm flexors and extensors in women was 55 % of that in men. This figure is higher than the figures reported in this study. Examination of the range of variations shows that the total number of tests which gave percentages of 50-53 was only 9 out of 92 tests. It is interesting to note that the strength of women can be predicted with greater certainty from the strength of men than can the strength of extensor from the known strength of flexors in the same sex. Contrary to the findings by other investigators (4), extensors showed greatest strength not at the minimal length but when they were stretched, the elbow angle being 90” or less. This was true for both isotonic and isometric contractions, The
180
M.
present findings are in agreement sults obtained by the writers (7). and
This study Metabolic
was supported by Diseases Research
National Grant
with
AM
the previous Institute 06724.
of
re-
Present
address
Physical Canada.
Education,
Received
for
of M.
SINGH
Singh:
AND
Fitness
University
P. V.
Research
of Alberta,
KARPOVICH Unit,
Faculty
Edmonton,
of
Alberta,
Arthritis publication
7 December
1967.
REFERENCES 1. CLARKE, H. H. Improvement of objective strength tests of muscle groups by cable-tension methods. Res. &arf. 21 : 399419, 1950. 2. CLARKE, H. H., E. C. ELKINS, G. M. MARTIN, AND K. G. WAKIM. Relationship between body position and the application of muscle power to movements of the joints. Arch. Hays. Med. 31: 81-89, 1950. 3. Doss, W. S., AND P. V. KARPOVICH. A comparison of concentric, eccentric, and isometric strength of elbow flexors. J. AppZ, Physiol. 20 : 3 15-353, 1965. 4. ELKINS, E. C., U. M. LEDEN, AND K. G. WAKIM. Objective
recording
of the strength 1951. 5. HETTINGER, T. phys&gy 1961.
of normal
muscles.
Arch. Hip. ikhi.
of Strength.
Springfield,
111. : Thomas,
32: 639-647,
6.
RASCH, mum flexors.
7. SINGH, forearm 1966,
P. J., isometric
AND W* tension
R. PIERSON. Relationship between and breaking strength of
Res. Q)uarf. 3 1 : 534-35, 1960. M., AND P. V. KARPOVICH. Isotonic flexors and extensors. J. LI@Z. Physiol.
and 21:
maxiforearm isometric 1435-37,
