Also avoid 4 hour practice sessions, break it up in to a few shorter ones if you are going to hard. It shouldn't hurt. Work on your ergonomics, don't be reaching, pushing too hard. It's all about being relaxed. That is why you are doing heel toe instead of singles. Perhaps your pedals are cranked way too tight.
I don't think there to tight .my spring adjusters are about dead center the vld is in the middle and my beaters are 5 "" from the drum head they are axis pedals btw. I tried heel toe with the vld forward like everyone recommends but had a hard time keeping the doubles going.thanks
It's been valuable in my case for working on heel up, since I was taught heel down and continue to use that as a primary technique for all styles (no Metal or double bass). I've not had cramps using heel down, but I don't have to stomp the beater for the music I play. If volume's really needed I'm able to use heel up in limited phrases.
Heel up felt extremely unnatural at first and was puzzling--its developing slowly (in part thanks to the DVD), along with endless practice. The goal is to be able to use both as needed.
I would assume the reverse if I had learned heel up from the start.