Appendicular skeletal muscle areas assessed by magnetic resonance imaging in older persons.

Measurements of cross-sectional muscle areas of the upper-arm and mid-thigh from MRI images were compared to corresponding estimates from anthropometric measurements of limb circumferences and skinfold thicknesses in 25 normal, healthy, elderly persons. The anthropometric method significantly overestimated actual muscle areas, and the amount of error increased systematically with level of adiposity. These results agree with those from other, similar studies using CT in younger adults, but indicate that the degree of error is 2 to 3 times greater for elderly persons. At present, there does not appear to be any simple way to "correct" the anthropometric method. Prediction methods may be developed, but these will still produce large errors for some individuals. Alternative approaches are discussed.