In my last post, I meant to warn against the idea that just because someone is successful, they're a knowledgeable exert. I also made a comment that, if misconstrued, could lead to another error. I said that what particular training a runner did does not matter; what someone else does should not matter to you, but what particular training he did was important to him and what particular training you do is important to you. The "It's all good" comment one often hears is misleading - all training is not equal.
I know several accomplished runners, including a national-class master, who say one just has to "keep changing things up, keep the body guessing, keep the muscles confused, never do the same things." This can work fairly well for runners so gifted that they can succeed without a plan. It also works well for beginners, for whom every workout is new and therefore equal. Many successful high school coaches use this method; teenagers prefer the novelty of always running new workouts and, because any one workout will work well for a few runners, fairly well for many and a little for most, constantly changing workouts gives everyone on the team some of what they need most, leading to an improvement in the team as a whole.
There are entire industries based on the "workout collector." People take classes in yoga, tai chi, Pilates and so forth - all useful disciplines - switching from one discipline to another or one instructor to another, always seeking the next challenge, never thinking about what they should do, never planning. Running magazines, and now websites, are based upon promoting the latest crazes and, if you jump on every bandwagon, you get a continuously varied approach, which, with enough followers, ill have its success stories (which are invariably reported).
Change is necessary. One needs to do a variety of workouts. What I'm advocating is to not have those changes be random, but evolutionary. Yes, evolution in nature involves random changes; in the same way, you need to select those changes that lead to success. Change without direction is chaos.