people no one here is 'flexible' enought to need a platform if they are done right. Like a few others have suggested these are done a slight bend in the knees but most importantly the lower back should be arched hard and the ass should be back as much as your flexability will allow. The hamstrings will be pre stressed this way and if you hold this position on the way down with the bar touching your thighs, you will not get past your knees, some of the less flexible will not make it to the knees