I forgot what topic it was that I first said this on, but look at this.
No-man's Land. In Figure 7, you will see that there are 3 shaded areas, between R and I, between I and T and between T and E. Except for MP (between T & E) these are "No man's land of training. Training intensities that fall into 'No man's land," are either too easy or too hard to reap the benefits you want. You are not, as may sometimes be assumed, achieving the purpose of training the two systems on either side of the chosen intensity. What you are doing might be termed, "Quality-junk" training. At the least, it is training aimed at accomplishing an unidentifiable purpose. Always have a purpose for every training session; ask yourself the following questions: "What system do I hope to improve by doing this workout,' and 'What am I really trying to accomplish?"