The range of aerobic power that people put out is pretty huge, its possible that at the extreme low end, having no glycogen to burn wouldn't be a limiter, but c

The range of aerobic power that people put out is pretty huge, its possible that at the extreme low end, having no glycogen to burn wouldn't be a limiter, but certainly at the moderately trained average joe level, it is still a limiter. But early on, you don't need to worry much about it, just get out and move every day. If you keep it up for a year or two, and want to get faster, you can start adding things to be neurotic about =)