View source for Anthropometry of the upper arm

{{short description|Set of measurements of the shape of the upper arms}}
{{Technical|date=September 2009}}

The '''anthropometry of the upper arm''' is a set of measurements of the shape of the upper arms.

The principal [[anthropometry]] measures are the '''upper arm length''', the '''triceps skin fold''' ('''TSF'''), and the ('''mid-''')'''upper arm circumference''' (('''M''')'''UAC''').  The derived measures include the ('''mid-''')'''upper arm muscle area''' (('''M''')'''UAMA'''), the ('''mid-''')'''upper arm fat area''' (('''M''')'''UAFA'''), and the '''arm fat index'''. Although they are not directly convertible into measures of overall [[body fat]] weight and density, and research has questioned the connection between skinfold fat and deep body fat measurements, these measures are and have been used as rough indicators of body fat.

Factors influencing the bone, fat, and muscle composition of the upper arm include age, sex, nutritional status, fitness training level, and race.

== Measures ==

[[file:mid-Upper-Arm Circumference Band.jpg|alt=doctor measures the arm of a child being held by a family member|thumb|A standardised measuring tape is used to ascertain the mid-upper arm circumference of a child]]

The anthropometric measures of the upper arm are divided into principal measures, which are measured directly, and derived measures, which are derived from the principal measures using specific formulae and empirically-derived corrections.  The derived measures attempt to provide better indicators of body composition and nutritional status than the principal measures, by accounting for the fact that external measurements of the arm necessarily compound measurements of bone, fat, and muscle.<ref name=Shepard1>{{cite book|title=Body composition in biological anthropology|volume=6|series=Cambridge Studies in Biological and Evolutionary Anthropology|author=Roy J. Shephard|publisher=Cambridge University Press|year=1991|isbn=9780521362672|pages=24&ndash;25|chapter=Epidemiological indices, anthropometric and cadaver estimates of body composition}}</ref>

=== Principal measures ===
The three principal anthropometric measures of the upper arm are the upper arm length, the triceps skin fold (TSF), and the mid-upper arm circumference (MUAC).

The triceps skin fold is the width of a fold of skin taken over the [[triceps]] muscle.  It is measured using skinfold [[caliper]]s.  (See [[body fat percentage#Skinfold methods]] for general information on skinfold fat measurements.)  The measurement is taken at a standardized position (one of eight standard skinfold measurement points) at the midpoint of the back of the upper arm.<ref name=DeYoung>{{cite book|title=Foundations and clinical applications of nutrition: a nursing approach|author1=Michele Grodner|author2=Sara Long|author3=Sandra DeYoung|editor=Sandra DeYoung|edition=3rd|publisher=Elsevier Health Sciences|year=2004|isbn=9780323020091|pages=[https://archive.org/details/foundationsclini0000grod_n0m8/page/406 406&ndash;407]|chapter=Nutrition in Patient Care|chapter-url=https://archive.org/details/foundationsclini0000grod_n0m8/page/406}}</ref><ref name=Zemel1>{{cite book|author1=Alisha J. Rovner |author2=Babette Zemel |chapter=Growth and Physical Maturation|title=Pediatric Drug Development: Concepts and Applications|editor=Andrew E. Mulberg |editor2=Steven A. Silber |editor3=John N. van den Anker|publisher=John Wiley and Sons|year=2009|isbn=9780470169292|pages=370}}</ref>  The skinfold calipers are spring-loaded.  Holtain skinfold calipers are marked with 0.2&nbsp;mm [[Calibration|gradation]], and Lange calipers with 0.5&nbsp;mm gradation.<ref name=Zemel1 /><ref name=Zemel2 />

The measurement is taken with the person standing upright, with arms hanging down loosely.  The skin fold is pulled away from the muscle and measured with the calipers, taking a reading 4 seconds after the calipers have been released.<ref name=Zemel1 /><ref name=Zemel2 />  The measuring point is halfway between the [[olecranon process]] of the [[ulna]] and the [[acromion process]] of the [[scapula]].<ref name=Zemel2>{{cite book|author=Babette Zemel|chapter=Assessment of Growth and Nutritional Status in Pediatric Inflammatory Bowel Disease|title=Pediatric Inflammatory Bowel Disease|url=https://archive.org/details/pediatricinflamm00mamu_778|url-access=limited|editor1=Petar Mamula |editor2=Jonathan E. Markowitz |editor3=Robert N. Baldassano |publisher=Springer|year=2007|isbn=9780387734804|pages=[https://archive.org/details/pediatricinflamm00mamu_778/page/n314 299]&ndash;301}}</ref><ref name=Bogin>{{cite book|title=Patterns of human growth|volume=23|series=Cambridge studies in biological and evolutionary anthropology|author=Barry Bogin|edition=2nd|publisher=Cambridge University Press|year=1999|isbn=9780521564380|pages=87&ndash;88}}</ref><ref name=Frisancho>{{cite book|pages=17&ndash;18,20&ndash;23|title=Anthropometric standards for the assessment of growth and nutritional status|author= A. Roberto Frisancho|author-link= A. Roberto Frisancho|publisher=University of Michigan Press|year=1990|isbn=9780472101467}}</ref>

The mid-upper arm circumference is the [[circumference]] of the upper arm at that same midpoint, measured with a non-stretchable [[tape measure]]<ref name=DeYoung /><ref name=Zemel1 /><ref name=Zemel2 /><ref name=Frisancho /> or [[3D print]]able bands.<ref>3-D printing open-source click-MUAC bands for identification of malnutrition. ''Public Health Nutrition'', doi:10.1017/S1368980017000726 [https://www.academia.edu/32956588/3-D_Printing_Open_Source_Click-MUAC_Bands_for_Identification_of_Malnutrition open access]</ref>

=== Derived measures ===
The derived anthropometric measures include the mid-upper arm muscle area (MUAMA), the upper arm fat area (UFA), and the arm fat index.

The mid-upper arm ''area'' (MUAA) is an estimation of the area of the upper arm.  It is derived from the MUAC using the following formula:<ref name=Zemel1 /><ref name=Zemel2 />
*<math>MUAA = \frac{MUAC^2}{4 \pi}</math><ref name=Zemel1 /><ref name=Zemel2 /><ref name=Frisancho />

The mid-upper arm ''muscle'' circumference (MUAMC) is an estimation of the circumference of the bone and muscle portions of the upper arm.  It is derived from the MUAC and the TSF by accounting for the thickness of the subcutaneous fat that surrounds the muscle, using the following formula, with the MUAC and TSF values measured in millimetres:<ref name=DeYoung />
*<math>MUAMC = MUAC - \left ( \pi \times \frac{TSF}{10} \right )</math><ref name=DeYoung />

The mid-upper arm muscle ''area'' (MUAMA) is an estimation of the area of the bone and muscle portions of the upper arm.  It is derived from the MUAMC using the following formula, with the MUAMC as above:<ref name=DeYoung />
*<math>MUAMA = \frac{MUAMC^2}{4 \pi}</math><ref name=DeYoung /><ref name=Zemel1 /><ref name=Zemel2 /><ref name=Frisancho />

The ''corrected'' mid-upper arm muscle area (CMUAMA) is an estimation of the area of the muscle portions of the upper arm, attempting to eliminate the area due to bone.  It is derived from the MUAMC using the following two formulae, with the MUAC and TSF values measured in centimetres:<ref name=DeYoung />
*For men: <math>CMUAMA = \frac{\left ( MUAC - \left ( \pi \times \frac{TSF}{10} \right ) \right )^2 - 10}{4 \pi}</math><ref name=DeYoung />
*For women: <math>CMUAMA = \frac{\left ( MUAC - \left ( \pi \times \frac{TSF}{10} \right ) \right )^2 - 6.5}{4 \pi}</math><ref name=DeYoung />

The mid-upper arm ''fat'' area (MUAFA) is an estimation of the area of the far portions of the upper arm, and is simply the difference between the MUAA and the MUAMA:<ref name=Frisancho />
*<math>MUAFA = MUAA - MUAMA</math><ref name=Frisancho />

From the MUAFA is derived the arm fat index (AFI), a percentage of the arm that is fat, using the following formula:<ref name=Frisancho />
*<math>AFI = 100 \times \frac{MUAFA}{MUAA}</math><ref name=Frisancho />

== Theory and practice ==
{{Expand section|date=September 2009}}

=== Validity ===
The sex-specific constant correction values in the corrected MUAMA formulae are derived from empirical studies.  The MUAMA formula assumes that the upper arm has a circular cross-section, with a uniform subcutaneous fat layer and negligible bone content.  This is, of course, not the case in reality.  The correction factors are attempts to discount the contribution of the [[humerus]].  By comparing MUAMA values against [[computed tomography]], studies by Heymsfield et al. found that, at the maximum circumference of the triceps, the contribution of bone to the total cross-sectional area was 18% in men and 17% in women, which were 10&nbsp;cm<sup>2</sup> and 6.5&nbsp;cm<sup>2</sup> respectively.<ref name=Shepard1 />

Even the corrected MUAMA formulae are not valid for people who are obese or for older people.<ref name=DeYoung />  They tend to overestimate muscle area for obese people.<ref name=Frisancho />  The results of the formulae can contain small but significant errors in the cases of young people, and errors of up to 41.5% for older people.<ref name=Conn>{{cite book|pages=[https://archive.org/details/handbookmodelsfo00conn_512/page/n952 982]|title=Handbook of models for human aging|url=https://archive.org/details/handbookmodelsfo00conn_512|url-access=limited|editor=P. Michael Conn|publisher=Academic Press|year=2006|isbn=9780123693914|author=Alfred L. Fischer|chapter=Models of sarcopenia}}</ref>  Moreover, the size of the humerus is not in fact equal in all individuals.<ref name=Bogin />  It also varies with nutritional status.<ref name=Shepard1 />

The formulae for the derived measures are based upon an assumption that the arm is cylindrical in shape, and are thus based upon the simple geometry of a [[Cylinder (geometry)|cylinder]]. The arm is not in fact an ideal cylinder.  However, the assumptions of the formulae yield results that are close enough to the actual reality that the measurements are reliable and accurate when averaged over groups of people.<ref name=Bogin />

The principal measurements are also subject to error.  Taking a triceps skin fold measurement too frequently or for too long can result in compression of the tissue, and false readings, for example.<ref name="Judith2007">{{cite book|title=Handbook of physical measurements|url=https://archive.org/details/handbookphysical00hall_476|url-access=limited|author1=Judith G. Hall |author2=Judith Allanson |author3=Karen Gripp |author4=Anne Slavotinek |edition=2nd|publisher=Oxford University Press US|year=2007|isbn=9780195301496|pages=[https://archive.org/details/handbookphysical00hall_476/page/n79 67]}}</ref>  Even which arm is measured matters, since mid-upper arm circumference is generally greater on the dominant arm (e.g. the right arm for right-handed people).  Few studies make specific note of which arms were measured.<ref name="Rebecca2003">{{cite book|pages=[https://archive.org/details/diseaserelatedma0000stra/page/50 50]|title=Disease-related malnutrition: an evidence-based approach to treatment|url=https://archive.org/details/diseaserelatedma0000stra|url-access=registration|author1=Rebecca J. Stratton |author2=Ceri J. Green |author3=Marinos Elia |publisher=CABI|year=2003|isbn=9780851996486}}</ref>

=== Evaluation ===
The various measures are evaluated against anthropometric reference data tables, such as those derived from the [[National Health and Nutrition Examination Survey]] data.<ref name=DeYoung /><ref name=Zemel1 /><ref name=Zemel2 />
Mid-upper arm circumference (MUAC) measurement, if conducted by well-trained staff, can give a quick assessment of new arrivals at a refugee camp during a humanitarian crisis. It is based on the observation that this measurement does not change much in children between 6 months and five years old, so comparison to a "normal" measurement is useful. Based on analysis of field results, MUAC < 125mm corresponds to [[Global Acute Malnutrition]] and MUAC < 115mm with or without [[Oedema]] corresponds to [[Severe Acute Malnutrition]].<ref>{{cite book |title=Travel medicine and migrant health |author=Cameron Lockie |publisher=Elsevier Health Sciences |year=2000 |isbn=0-443-06242-0}}</ref>

=== Correlation ===
The various measures have been shown to have correlation to other measurements of body fat, including those derived from [[X-ray absorptiometry]].<ref name=Zemel1 /><ref name=Zemel2 />

However, the relationship between measurements of subcutaneous fat in skinfolds, such as the triceps skinfold, and deep body fat have been questioned.  Early research in the 1960s found a positive correlation between the two, and the skinfold measurements do provide a reasonable estimate of the deep body fat.  However, research in the 1980s used computed tomography to measure deep fat, and showed a lack of correlation between that and subcutaneous fat.  However, for children and adolescents the skinfold and circumference measurements provide a fair assessment of total body fat because that is where most body fat lies during those stages of human growth.<ref name=Bogin />

== Variations ==
{{Expand section|date=September 2009}}
Many factors influence the bone, fat, and muscle composition of the upper arm, and their measurements can vary by age, gender, obesity, fitness training status, and race.  (This is one reason that anthropometrists have to be careful about what reference data and correction values they employ for individuals.)<ref name=McArdleKatches>{{cite book|title=Exercise physiology: energy, nutrition, and human performance|author1=William D. McArdle |author2=Frank I. Katch |author3=Victor L. Katch |edition=6th|publisher=Lippincott Williams & Wilkins|year=2007|isbn=9780781749909|pages=794&ndash;795}}</ref> The [[World Health Organization]] uses arm circumference-for-age as an anthropometric indicator for its Child growth standards.<ref>{{cite web|url=https://www.who.int/tools/child-growth-standards/standards/arm-circumference-for-age|publisher=World Health Organization|title=Arm circumference-for-age|accessdate=September 7, 2021|archive-date=September 7, 2021|archive-url=https://web.archive.org/web/20210907234134/https://www.who.int/tools/child-growth-standards/standards/arm-circumference-for-age|url-status=live}}</ref>

One cause of age variations is the tendency for body fat to be deposited internally, rather that subcutaneously, as one ages.<ref name=McArdleKatches /><ref name="Dorothy2000">{{cite encyclopaedia|article=body composition|author1=Dorothy G. Herron|author2=Lynn B. Greenberg|pages=[https://archive.org/details/encyclopediaofel0000unse_r9n9/page/98 98]|encyclopedia=The encyclopedia of elder care: the comprehensive resource on geriatric and social care|editor=Mathy Doval Mezey|publisher=Springer Publishing Company|date=2000|isbn=9780826113689|url=https://archive.org/details/encyclopediaofel0000unse_r9n9/page/98}}</ref>

Nutritional factors include [[zinc]] intake, which has been shown to have effects on both the triceps skin fold thickness and the mid-upper arm circumference.<ref name="Ref_b">{{cite book|title=International public health: diseases, programs, systems, and policies|editor1=Michael H. Merson|editor2=Robert E. Black|editor3=Anne Mills|edition=2nd|publisher=Jones & Bartlett Publishers|year=2005|isbn=9780763729677|chapter=Nutrition|pages=[https://archive.org/details/isbn_9780763729677/page/227 227]|author1=Keith P. West Jr|author2=Benjamin Caballero|author3=Robert E. Black|url-access=registration|url=https://archive.org/details/isbn_9780763729677/page/227}}</ref>

==References==
{{Reflist}}

== Further reading ==
* {{cite journal|title=The triceps skinfold as a predictive measure of body density and body fat in obese adolescent girls|author1=Carl C. Seltzer |author2=Ralph F. Goldman |author3=Jean Mayer |journal=Pediatrics|volume=36|issue=2|date=August 1965|pages=212&ndash;218 |doi=10.1542/peds.36.2.212 | pmid = 14320030 |s2cid=27667457 }}
* {{cite book|title=Human body composition|editor=Steven Heymsfield|edition=2nd|publisher=Human Kinetics|year=2005|isbn=9780736046558|chapter=Assessing Muscle Mass|author=Henry C. Lukascki}}
* {{cite journal|title=Anthropometric measurement of muscle mass: revised equations for calculating bone-free arm muscle area|journal=American Journal of Clinical Nutrition|volume=36|issue=4|pages=680&ndash;690|year=1982|author1=Steven B. Heymsfield |author2=Clifford McManus |author3=Janet Smith |author4=Victoria Stevens |author5=Daniel W. Nixon |doi=10.1093/ajcn/36.4.680|url=http://ajcn.org/cgi/reprint/36/4/680.pdf | pmid = 7124671 }}
* {{cite journal|journal=American Journal of Clinical Nutrition|volume=52|pages=591&ndash;595|publisher=The American Society for Clinical Nutrition, Inc.|title=Validity of surface anthropometry to estimate upper-arm muscularity, including changes with body mass loss|author1=F.I. Katch |author2=T. Hortobagyi |url=http://ajcn.org/cgi/content/abstract/52/4/591|pmid=2403053|issue=4|year=1990|doi=10.1093/ajcn/52.4.591}}
* {{cite journal|title=Upper-Arm Anthropometry: An Alternative Indicator of Nutritional Health to Body Mass Index in Unilateral Lower-Extremity Amputees?|journal=Archives of Physical Medicine and Rehabilitation|volume=89|issue=10|pages=2031&ndash;2033|author1=M. Miller |author2=W. Wong |author3=J. Wu |author4=S. Cavenett |author5=L. Daniels |author6=M. Crotty |date=October 2008|doi=10.1016/j.apmr.2008.03.025|pmid=18929034}}
* {{cite journal|author1=F. E. Johnston |author2=R. M. Malina |year=1966|title=Age changes in the composition of the upper arm in Philadelphia children|journal=Human Biology|volume=38|issue=1|pages=1&ndash;21 | pmid = 5908112 }}
* {{cite journal|journal=American Journal of Physical Anthropology|volume=36|issue=3|pages=341&ndash;351|title=Reduced sexual dimorphism in upper arm muscle circumference associated with protein-deficient diet in a South American population|author=William A. Stini|year=1972|doi=10.1002/ajpa.1330360304 | pmid = 5035060 }}
* {{cite journal|journal=Annals of Human Biology|date=November–December 1981|volume=8|issue=6|pages=495&ndash;517|title=Radiographically determined widths of bone muscle and fat in the upper arm and calf from age 3&ndash;18 years|author1=J.M. Tanner |author2=P.C. Hughes |author3=R.H. Whitehouse |pmid=7337414|doi=10.1080/03014468100005351}}
* {{cite book|title=Handbook of nutrition and food|editor1=Carolyn D. Berdanier |editor2=Johanna T. Dwyer |editor3=Elaine B. Feldman |edition=2nd|publisher=CRC Press|year=2007|isbn=9780849392184|chapter=Frame Sizes, Circumferences, and Skinfolds|author=Barbara J. Scott}}
* {{cite book|pages=441&ndash;446|chapter=Nutritional Assessment of the Elderly § Anthropometric Assessment|author1=Carol O. Mitchell-Eady |author2=Ronni Chernoff |title=Geriatric nutrition: the health professional's handbook|editor=Ronni Chernoff|edition=3rd|publisher=Jones & Bartlett Publishers|year=2006|isbn=9780763731816}}
* {{cite journal|author=T.G. Lohman|year=1981|title=Skinfolds and body density and their relation to body fatness. A review.|journal=Human Biology|volume=53|issue=2|pages=181&ndash;225 | pmid = 7239496 }}
* {{cite book|chapter=Human body composition|author1=Michael R. Hawes |author2=Alan D. Martin |title=Kinanthropometry and exercise physiology laboratory manual|volume=1: tests, procedures and data|editor1=Roger Eston |editor2=Thomas Reilly |edition=2nd|publisher=Routledge|year=2001|isbn=9780415236133|pages=21&ndash;22}}

{{Human anatomical features}} 
{{Upper limb general}}
{{Authority control}}

[[Category:Anthropometry]]
[[Category:Arm]]