From measurement of the arm muscle area, it is possible to approximate the total body muscle mass. The mid-arm circumference is adjusted for the tricep skin fold thickness to adjust for subcutaneous fat. Further corrections are needed to adjust for the presence of bone and for the assumption of a circular mid-arm muscle compartment.
Technique:
(1) The mid-arm circumference is measured in centimeters midway between the olecranon process and the acromium.
(2) The triceps skin fold is measured in millimeters with calipers at the same level as the mid-arm circumference, on the posterior of the arm, over the long head of the triceps brachii.
uncorrected arm muscle area in cm^2 =
= ((((midarm circumference in cm) - (π * (triceps skin fold thickness in cm))) ^2) / (4 * π))
corrected arm muscle area in cm^2 for men =
= ((((midarm circumference in cm) - (π * (triceps skin fold thickness in cm))) ^2) / (4 * π)) - 10
corrected arm muscle area in cm^2 for women =
= ((((midarm circumference in cm) - (π * (triceps skin fold thickness in cm))) ^2) / (4 * π)) - 6.5
Notations:
• The triceps skin fold thickness is typically measured in millimeters. It is converted to centimeters for these equations.
Interpretation:
• The average error for arm muscle area by the equations is 7-8%.
• The minimum range for arm muscle area compatible with survival is 9-11 cm^2, with values < 9 cm^2 associated with death.
Limitations:
• The precision in performing skin-fold thickness measurements varies with the measurer, the site assayed, and the size of the subcutaneous fat mass.
• Edema and nonuniform fat distribution may result in misleading results.
• Skin-fold thickness is relatively insensitive to acute changes in nutritional status.
• The equations were developed for patients 20-70 years of age and may not apply to children, as the subtracted factor may be too large.
Upper Arm Muscle Area in square millimeters in Normal Whites (Frisancho)
|
|
Men |
Women |
||||
|---|---|---|---|---|---|---|
|
Age |
5th% |
50th% |
95th% |
5th% |
50th% |
95th% |
|
1-1.9 |
956 |
1278 |
1720 |
885 |
1221 |
1621 |
|
2-2.9 |
973 |
1345 |
1787 |
973 |
1269 |
1727 |
|
3-3.9 |
1095 |
1484 |
1853 |
1014 |
1396 |
1846 |
|
4-4.9 |
1207 |
1579 |
2008 |
1058 |
1475 |
1958 |
|
5-5.9 |
1298 |
1720 |
2285 |
1238 |
1598 |
2159 |
|
6-6.9 |
1360 |
1815 |
2493 |
1354 |
1683 |
2323 |
|
7-7.9 |
1497 |
2027 |
2886 |
1330 |
1815 |
2469 |
|
8-8.9 |
1550 |
2089 |
2788 |
1513 |
2034 |
2996 |
|
9-9.9 |
1811 |
2288 |
3257 |
1723 |
2227 |
3112 |
|
10-10.9 |
1930 |
2575 |
3882 |
1740 |
2296 |
3093 |
|
11-11.9 |
2016 |
2670 |
4226 |
1784 |
2612 |
3953 |
|
12-12.9 |
2216 |
3022 |
4640 |
2092 |
2904 |
3847 |
|
13-13.9 |
2363 |
3553 |
4794 |
2269 |
3130 |
4568 |
|
14-14.9 |
2830 |
3963 |
5530 |
2418 |
3220 |
4850 |
|
15-15.9 |
3138 |
4481 |
5900 |
2426 |
3248 |
4756 |
|
16-16.9 |
3625 |
4951 |
6980 |
2308 |
3248 |
4946 |
|
17-17.9 |
3998 |
5286 |
7736 |
2442 |
3336 |
5251 |
|
18-18.9 |
4070 |
5552 |
8355 |
2398 |
3243 |
4767 |
|
19-24.9 |
4508 |
5913 |
8200 |
2538 |
3406 |
4940 |
|
25-34.9 |
4694 |
6214 |
8436 |
2661 |
3573 |
5541 |
|
35-44.9 |
4844 |
6490 |
8488 |
2750 |
3783 |
5877 |
|
45-54.9 |
4546 |
6297 |
8458 |
2784 |
3858 |
5964 |
|
55-64.9 |
4422 |
6144 |
8419 |
2784 |
4045 |
6247 |
|
65-74.9 |
3973 |
5716 |
7453 |
2737 |
4019 |
6214 |
ICD-10: ,
