Anthropometry of the upper arm

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

The MUAMA formula assumes that the upper arm has a circular cross-section, with a uniform subcutaneous fat layer and negligible bone content.

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 cm2 and 6.5 cm2 respectively.

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.

Taking a triceps skin fold measurement too frequently or for too long can result in compression of the tissue, and false readings, for example.

[2][3][4] 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.

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.

[5] 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.

)[12] The World Health Organization uses arm circumference-for-age as an anthropometric indicator for its Child growth standards.

[12][14] 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.