In the assessment manual there is no mentioning of the placement of the feet. What it says is: "maintain neutral spine avoiding excessive arching of the back". No further explanation. My very old, 1998, BP manual gives the option of lifting the feet, knees are over the hips, donot cross your feet. No further explanation. As we all know LM goes for safety when working out. "Safe" , in working out terms, is a "closed kinetic chain", ie feet on the floor. Once you lift your feet, you shorten your iliopsoas and lengthen your erector spinae. This releaves tension in the lower back, ie the part between lower rib and the crista iliaca. BUT this can also cause flexion of the spine in the lumbar area when incorrectly using your abd. and upper back muscles. Lying on a step is not a "normal" position, because your but is higher then your feet, this means you have to work harder with your abs and upper back to keep your spine in neutral. People with weak abs, long, and strong, short, back muscles WANT to lift there feet or put their heels on the step, because this position gives them a feeling of lying in a "normal" supine position. My step is not higher than one brick, allthough I am strong and know exactly how to work my muscles to keep my spine in "neutral". These arguments are based on my knowledge and experience as a cert. STOTT PILATES instructor. I wish I could spill my knowledge in my own language .... ! LM does not want you to follow them blindly, they want you to THINK, LEARN and use your COMMON SENSE ! I therefore always after class ask why and than look at the posture of a participant when this person lifts the feet. My generaI cue always is feet on the floor because this engages the abs etc. more ! And done correctly makes the muscles stronger. Thanks for reading and trying to understand ....