Cycling will certainly help, I'm a biker in the summer so when I get back on the board in the winter the steadfast leg transition is much faster. Other then that though your just gonna have to snowboard a shitload and deal with the pain, because you will be working those specific muscles you use for snowboarding, muscles you dont always use alott for anything else. For example skiing is a completely different muscle set. I popped on some skis at the end of this season and got tired really fast, even after having my legs be monsters for boarding.
PowderHound and TreeNinja