Upper Arm Muscle Circumference
Circumferences can be used as indicators for the quantity of fat and muscle mass in the body. The upperarm muscle circumference (S) is a measure for muscle mass in the body measured together with the triceps skinfold (T). In this method the assumption is that the measured muscle circumference is representative for the rest of the body.
Besides that it is assumed that there is an equal distribution of fat around the arm and that there is a constant amount of bone compared to the muscle area.
Upperarm fat mass (F), also measured by upperarm circumference measured together with the triceps skinfold (T), provides a better determination of the total body fat mass than a single skinfold measurement. The thickness of the triceps skinfold and the area of the upperarm diminish if the patient has malnutrition. Repeated measurements can give us an indication about changes in body composition and nutritional state of the patient.
Frisancho A.R. (1981) has published some tables with percentiles, which can be used to compare the measured values with the values of a general population. As a patient can be compared to the low percentiles, than he or she belongs to the skinny people.
McWhirter (1994) demonstrated in his research that an upperarmmusclecircumference below P15 shows that we can speak about malnutrition. Below the 5th percentile it’s severe malnutrition.
These values are, however, not a very reliable measure. When a patient has a constant upperarm muscle circumference (for example p60) and it drops to P50, malnutrition is a possibility although the muscle circumference is not below P15. The change in time is a better measure for the nutritional state.
The disadvantage of this method is that the results are not reliable patients with oedema in the upper extremities or people who are immobile by muscle disease or something else.
c = upperarmcircumference in mm
T = triceps skinfold in mm
p = 3.14
Reference-tables in percentiles Frisancho A.R. (1981): click on the links.
Measurements of the upperarm circumference and triceps skinfold:
Measuring the upperarm circumference and triceps skinfold is easy to perform, not painful for the patient and cheap.
The middle of the upperarm is measured using a measuring tape (Frisancho: right arm).
The triceps skinfold in mm is measured in the middle on the backside of the right upperarm (Frisancho).
Reference values for upperarm circumference, upperarm muscle circumference and triceps skinfold are also published by Jelliffe (1966) and are often used as a reference. These reference value however are often criticised and references published by Frisancho (1974/ 1981) were recommended because the values were taken by a more representative population. Comparison is made by Harries (1982) and showed that there is no similarity between the two. It’s always important to mention which reference is used.
Ravasco (2002) describes in his article that upperarm circumference is a useful tool to determine the nutritional state of ICU patients. The criteria from Mcwhirter (1994) and Blackburn (1977) were used. Muscle mass was measured on the non-dominant arm and was classified in three categories: normal, middle and severe depleted.