
Engineering Anthropometry and Biomechanics 23
4. Avoid long cushion length: Figure 2.6 (upper gure) shows that with a very long seat cush-
ion, a seated person will leave a gap behind the user’s buttocks and the lumbar region of the
seatback. The seat cushion length should be shorter than the buttock-to-popliteal length of
the person so that the user can support some of his or her upper body weight on the seat-
back and thus reduce L5/S1 load (see Figure 2.6, lower gure). Thus, if the seat cushion
length is not adjustable, then it is best to design the seat cushion length for the shorter (fth
percentile) female buttock-to-popliteal lengt ...