One thing I am trying to do this year is "ride to failure" - keep pushing the pace (normally TT or just below) and ride until I cannot push the pedal anymore. It is actually harder than I thought. The body is complaining. It is uncomfortable but I can actually go on. So far I have been doing these SST (90% of TT power) drills and it was only last night when my calf cramped up so bad I have to stop.
If I do these same drills on the road I have to save some effort so I can ride home. Going on a trainer gives me more leeway to "dig deeper".