Originally Posted by Derek Roddy
Flat foot is still heel up. I use that term because I don't angle my feet. The entire surface of my foot hits the pedal at the same time. It's the same thing that everybody I've ever seen play a bass drum does.( accept for the heel down players) Maybe the angles are different from player to player but at the end of all of that.... is still only one "techinque".
This quote, from the man himself is important because there is a lot of misinformation out there which tries to explain that 'flat foot' technique is something altogether different from heel up.
Technique A). What flat-foot technique ISN'T: using only the muscles in your hips/butt to lift the entire weight of your thigh, calf and foot up in the air, and the antagonistic muscle pair plus the aid of gravity to bring said bodily structures back down, consequently depressing the bass drum pedal.
Technique B). What flat-foot technique IS: using the muscles in your calves, just like in regular heel up, albeit at a slightly flatter angle which Derek happens to find more comfortable playing at.
NOTE - using your calf muscles in the way described in 'Technique B).' will still cause your leg to be raised into the air, so these two techniques essentially, look the same, but feel very different.
I think, the use of the term 'hip-flexor muscles' is what throws people off into thinking that flat foot technique is 'Technique A).' where you're lifting your whole thigh into the air from the hip. The hip flexors may well be involved in flat foot technique, but only as a stabilizing muscle ie. so you don't fall off your stool.
If flat foot technique is as the quote from Derek above says - then the muscles driving the action of the technique will still be the muscles of the calf - again, just like regular heel up.
Seriously, try playing Technique A). - I guarantee you will be struggling to play with any consistency, you will be off-balance, and you may even get back-ache.