Modeling dynamic skinfold compression

Real time compression of skinfolds was measured at three sites (triceps, abdominal medial calf), using a Slim Guide skinfold caliper adapted by the addition of a potentiometer, on eight males and eight females (age range 18-40 years). An average of eight trials for each subject at each site was used in modeling the compression curves. A mechanical model was developed, comprised of two parallel spring and viscous components in series with each other. $ Tt = Tinitial + F \left( { 1 \over k_1 } - \left\lceil { e { -k_1 t \over b_1 } \over k_1 } \right\rceil \right) + F \left( { 1 \over k_2 } - \left\lceil { e { -k_2 t \over b_2 } \over k_2 } \right\rceil \right) $ where: Tt = thickness at time t; Tinitial = intial skinfold thickness; F = force exerted by caliper; k(1) and k(2) = coefficients of elasticity; b(1) and b(2) = coefficients of viscosity. This two-component model was the best fitting model in comparison to one or three component alternatives. The coefficients of the model were different by sex and skinfold site. Coefficients for females showed greater elasticity and less viscosity compared to those for males. Further, there appeared to be a systematic site difference with the triceps having less elasticity and viscosity in both sexes. Am. J. Hum. Biol. 11:531-537, 1999. Copyright 1999 Wiley-Liss, Inc.