I want to get my legs up to speed when playing the double bass. Currently I'm playing heel up as I'm able to get more power and speed this way. But I think that playing heel down builds up the muscles more. Is this true? If so I'm willing to change it around so I'm able to build my chops.

youre right about heel down buidling up more chops.. but also another thing is that you have more control with heel down and you're able to play more dynamically, especially more on the quiet side. i suggest you continue to practice it because ull never forget how to pound away heel up.

heel down for more control, heel up for more speed and umph

[DRUMMER111]

depends on what the music is asking just like rock on said

i think it's better to practice heel down to give you more control overall.. also check out steve smith's dvd, history of the us beat. He explain bass drum technique thoroughly for smooth action