I need a little help settling an argument with a friend. My friend claims that you MUST log base miles (i.e. 3-4 hour Zone 1-2 ride) in the off-season to have a successful racing season. If your primary focus for the upcoming season is time trailing, which are no longer than one hour, why would one need to log 4 hours training at a lower heart rate? Wouldn't it make more sense to train at zone three, four, and five for two hours?