My trainer and treadmill (yes, I run) are my secret training weapons in the offseason. When I only get in like 50 road miles per MONTH if I'm lucky due to work and family, efficiency counts for everything, and that's where these two weapons are unbeatable. No junk miles, just quality butt kicking, with great data reproducibility so I know when I'm slacking and when I'm improving. My coriding buds are always a bit horrified when I join them for the rare outdoor rides and manage to drop them on the hills even though they're outdoors way more than I am. Doing Sufferfest intervals counts for a LOT for training!