Wild amount of Cadence Increase to Maintain Target Power in Tacx Training Plan

Throughout my simple (beginner) training workout found in Tacx training plan, I had to keep going up the gear set until I ran out. Even with the heaviest gear sets (though it helped to bring up the power very briefly), pedaling faster and faster seems the only viable solution to reach and briefly maintaining the target power during the training workout before the power started dropping again. Maintaining my target power output with any given cadence range seems very daunting at this point, if not impossible.  With current firmware update (4.5), I wonder if there are anything else I could try in order to keep my training/target power relatively steady ? Thanks a lot guys.