That was my reply when an athlete I started coaching only a few weeks ago enquired why his weekly schedule was the same as last week. This might seem shocking to some, but I often prescribe the same week two, three and even four weeks in a row. And why not? Given that the adaptations to training are also a function of, among other things, the level of fatigue the athlete is experiencing, the same week is never the same week. In fact, I can think of dozens of reasons why the same week is never the same week. The same week is perhaps more difficult to accomplish the second or third time around, which might indicate that the level of training we aimed for was probably too optimistic. Or maybe the first week of a block of training was hardly challenging and then it would be foolish to repeat that week.
Repetition is also your friend as a means to challenge and motivate. Having the same workouts from week to week is an excellent way to push for improvement, instead of just wondering if improvement is happening or not. Many times an athlete will only “nail” a workout after trying that workout a second or third time, and that can be give him/her great confidence. This obviously only works when you can measure pace or power accurately, so that improvement can be unequivocally checked.
So when does repetition stop being your friend? Well, basically when it stops serving its purpose, which is to help in the adaptation to new training stimulus. The training principle of biological adaptation tells us that in order for continued improvement, the training stimulus should be changed every 6 to 8 weeks, by manipulating either volume or intensity individually, or both at the same time. So repetition stops being an athlete's friend after he/she has reached a new level of adaptation to training.
So go ahead, find a week structure that you can stick to it for some weeks straight. Every week, even if it’s the same workout, push yourself a little further, go a little harder, push the boundary a little bit. Stick to it and be patient. You will soon reap the fruits of this approach.