I turbo twice a week in the winter, both interval sessions, first 1; 10min warm up folllowed by 10 sets of 30 seconds max effort followed by 30 seconds recovery, 10 minutes warm down. That REALLY HURTS!! Second; warm up and cool down the same, intervals 18 sets of 15 seconds max effort, 45 seconds recovery. they are short and punchy and you will feel and see the difference in your legs within a month. Then its whenever you can ride for long steady effort rides. Its all about being able to push a big gear for extended periods before you fatigue your muscles.