My martial arts background primarily includes a system of karate derived from Wado-ryu, Traditional Wing Chun, and Bujinkan Budo Taijutsu. Although these styles differ in many ways, one thing they all have in common is that they encourage students to keep both of their feet flat on the ground at all times (save for kicking). In my limited time spent training in MMA and Krav Maga, I was instructed to lift the heel of my back foot off the ground in order to deliver certain strikes. I have also observed that in videos posted on this forum by Iain and other's, many karateka also lift up their back heels for certain strikes.
What are the benefits of lifting the back heel? In my experience, we were instructed to keep our feet relatively flat as a way of staying rooted. Do the benefits of lifting the heel off the ground outweigh any potential detriments? Are their detriments? Do you believe that their is a correct attitude regarding the role of the back heel?
Please help satisfy my curiosity.