Complements your road rides with nice intervals. Of course you could define them on your own but having a virtual coach firing you on and telling you which gears to ride in is just more convenient.

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I finally gave in this winter and got some tapes to work out on the trainer. I figured living in the South you wouldn't need it much but it has been a real life safer. I must say that the trainer workouts with these tapes actually complement actual road training very well. I am using 4 different Spinervale tapes at teh moment. Uphill grind is my favorite evening workout, the time-trial special is a great rainy weekend day workout, the Zook challenge and the suffer-o-rama are great morning workouts. 45 minutes of great exersise. If you are looking for a quick intense workout this is the one.