Initial tudies on the variations of load-displacement curves of in vivo human healthy heel pads

Abstract

The aim of this study was to quantify on the measurement variation of in vivo load-displacement curves by using a group of human healthy heel pads. The recordings were done with a compression device measuring force and displacement. Twenty three heel pads, one from each of 23 subjects aged 20-35 years, were tested. The load-displacement curves showed the hysteresis, typical for a visco-elastic tissue. Seven load-displacement curves were measured for each subject. Each hysteresis was approximated by a 3rd degree polynomial, which in turn was described by two parameters: the slope and the average curvature. No statistically significant tendency (increasing or decreasing) were found for the seven polynomials (χ2 test, P-values of 0.81 and 0.17 for the two parameters, respectively). The study revealed no systematic error in the recorded load-displacement curves. The mean slope and the average curvature for the 23 subjects were found to be 6.02±1.54 N/mm and 0.02±0.01, respectively. The new apparatus shows its reliability for further clinical investigations. © 2011 Springer-Verlag.