I do what they say with my goal to improve my cadence as I develop strength. Sometimes I need to miss an interval because I need extra recovery time, but it is my time and my work-out, so I don't care. So if you need to change what they are doing on the tape then do it! If cogs are too difficult, simply raise it a cog or two and work your way down as you get stronger. For example, if they say big/15, then do big/17. It is an individual workout ... do what works for you so you get what you want out of the exercise and develop the way you need to!! Your time ... your bike ... your muscles ... your work-out!