Despite abundant knowledge about the relationship between body size (i.e., body mass, lower limb length) and limb posture during locomotion on the level of interspecies variability, little is known about variation on the intraspecific level. We used an experimental approach to evaluate the relationship between body size and knee posture during walking in humans at specific gait events and at each percentage point of normalized stance phase. We detected significant negative correlation between knee flexion angle and body mass at the second peak of the vertical ground reaction force, but, in contrast to a previous study, we found no significant relationship between knee flexion angle and lower limb length. Although not significant, strengthened correlations between knee flexion angle and lower limb length were detected at late stance phase and these coincide well with the strengthened correlations between knee flexion angle and body mass. Our findings support the view that body size influences limb posture during locomotion even on the intraspecific level. In humans, larger individuals tend to use more extended knee postures in late stance of walking than do smaller individuals.
Digitization of periosteal and endosteal contours of bone cross section is one of several methods used for calculating long bone cross-sectional geometry (CSG). In this study, invasively obtained bone histological samples were used to calculate intra-observer measurement error for CSG parameters. Intra-observer error was measured based upon repeated measurements of cross-sectional areas (total area [TA], cortical area [CA]) and moments of area (Imax, Imin, Imax/Imin, J) in B6CBA mice (n = 17). Cross sections were cut at 50 % of the biomechanical length of the left tibia and the samples were further processed for CSG and histological analysis. Intra-observer error was measured to estimate the accuracy of the digitization method. Accuracy of the tested digitization method was expressed by mean difference (MD), mean absolute difference (MAD), and limits of agreement (LA). The results confirm our assumption that intra-observer error decreases with the number of repeated measurement events. Thus, the error can be minimized by acquiring experience in the section digitizing. Our results also show that TA, CA and polar moment of area (J) are more susceptible to intra-observer error than are Imax, Imin and Imax/Imin.