VALIDITY OF AN ANTHROPOMETRIC ESTIMATE OF THIGH MUSCLE CROSS-SECTIONAL AREA

This study examined the validity of an anthropometric estimate of thig h muscle cross-sectional area using magnetic resonance imaging (MRI). The anthropometric model assumed that a cross section of the thigh cou ld be represented as a circle with concentric circular layers of fat-p lus-skin, muscle, and bone tissue. On 18 healthy, active men and women (mean +/- SD age = 23 +/- 5 yr), total thigh circumference (C-T) was measured with a fiberglass tape, fat-plus-skin thickness was measured over the quadriceps (S-Q) using calipers, and the distance across the medial and lateral femoral epicondyle (d(E)) was measured with caliper s. Direct measurements of each tissue were obtained by planimetry of a n MRT image taken at the same site as the circumference and skinfolds. Thigh muscle cross-sectional area (A(M)) was estimated as follows: [G RAPHICS] Mean +/- SD A(M) from MRI and anthropometry were 121.9 +/- 35 .1 cm(2) and 149.1 +/- 134.1 cm(2) (r = 0.96, SEE = 10.1 cm(2)), respe ctively. Errors in the anthropometric approximations of A(M) were due to an overestimate of the total thigh cross-sectional area and an unde restimate of fat-plus-skin compartment. Because of the close relations hip between MRT and anthropometric estimates of A(M), zero-intercept r egression was used to produce the following final equation, applicable for use in populations studies of young, healthy, active men and wome n: [GRAPHICS] y and anaerobic work capacity (20% MAS + 100% VO2peak) r esults in less variance in time to exhaustion than a method which extr apolates the submaximal power output-VO2 relationship to a supramaxima l intensity (120% VO2peak).