Always Maintain A High Level Of General Running Fitness
Prefabricated training plans are more or less obligated to assume that the runners using them are beginning at a relatively low fitness level relative to their own individual peak levels. Essentially, these plans assume you’re coming off a nice offseason break and are just beginning the process of establishing a fresh fitness base.
This assumption makes the plans more inclusive than they might otherwise be. A plan that assumed you already had a solid foundation of general running fitness would not work for you if you lacked that foundation, even if the peak training load prescribed in the final pre-taper weeks was appropriate for you given adequate time, because you’d be in over your head from the very start.
Every runner needs an offseason break, and every runner needs to take time to build a fresh fitness base after that break. But if you want to successfully execute a seasonal approach to racing that allows you to race at peak level several times between spring and fall, you need to maintain a fairly high fitness level at all other times. Doing so will enable you to return to peak form fairly quickly after each important race.
It’s important that you avoid training too hard for too long, however. If you try to sustain truly peak training loads throughout the racing season you will get injured or burn out. Except during the short periods when you are actively working to stimulate a fitness peak for an important race, your training should be “manageably hard.” In other words, the volume and intensity of training should be close to — but one solid step below — the maximum that you could sustain indefinitely without getting injured or burning out.
Give yourself a full week to relax and recuperate after major races, of course, but after that, get back after it. The exception, again, is marathons. After each marathon you need to treat yourself to a true offseason.