Further Applications - Preventive Biomechanics - page 351

Fig. 8.1 Skin tension lines: a L ANGER cleavage lines, b K RAISSL wrinkle lines, c B ORGES relaxed
skin tension lines (R STL ) and d principal R STL
Fig. 8.2 a FE buttock model on a bicycle saddle, b unloaded configuration in section cut view
and c loaded configuration of a lower buttock model in section cut view at the ischial tuberosity
(asymmetric loading: major load on right ischial bone; note excessive loading of the pelvic floor
musculature)
during body-saddle interaction, a distinct analysis of internal tissue stresses and
strains at all relevant tissue regions, i.e. gluteal skin, fat, muscle and bone, and
specifically arteries, by means of a dedicated human model turns out to be a
conditio sine qua non.
Previous investigations in the field of seat/ saddle evaluation have been
restricted to the use of pressure-mapping systems involving test subjects with
subjective perceptions or to the use of more or less rigid dummy devices both,
leading to insufficient non-objective information (human biological variability)
regarding tissue stress/strain distribution. In addition, such approaches do not
permit evaluation of internal tissue loadings.
Based on the B OSS -Procedure the loading of the affected tissues including
anatomical structures of the buttocks and pubic bone region are evaluated and
analyzed. Figure 8.2 shows an example of a lower buttocks model on bicycle
saddle as well as tissue and saddle stress distribution, Fig. 8.3 depicts the corre-
sponding skin tissue and saddle cover loading.