Most of the evidence shows that PH should be higher than the SH (Molenbroek and Ramaekers, 1996; Parcells et al., 1999) but it does not have to be higher than four centimeters (Gutie´ rrez and Morgado, 2001) or 88% of the PH (Parcells et al., 1999) in order to avoid compression in the buttock region (Garcı´a-Molina et al., 1992).