Do you want to discover which of your muscles have been "dead wood" all season long? Perform a set of one leg intervals on your trainer. Start out at 60 seconds/leg in the 39x19. This is harder than people realize. Add 30 seconds a week and as many gear inches as you can hold 90 rpm with. Later on, add sets (separated by 5 min recovery) You will find your abdominals and other core muscles becoming involved in the last 15 seconds of the effort.