This line of thinking promotes the notion that there is some sort of biological switching unit contained within muscle fibers and motor units that can tell the difference between the numbers 5 and 6. This theory presupposes that, as soon as something happens six times instead of five, a completely new and different mechanism comes into play for the body, and it shuts down strength development and kicks hypertrophy into hyperdrive. There is no middle ground or moderation, no spectrum of possibilities available, everything is simply binary and absolute.
The difference between the guy on the left and the guy on the right is just 1 rep per set
The reality we experience is that far more goes into play than simply rep ranges, and that, with other variables being manipulated, reps within the same range can produce a wide variety of effects. Rest times, sets, exercise selection, training frequency, recovery protocols, order of exercises and many other variables are incredibly relevant when it comes to determining the outcome of our training, and to try to achieve an outcome by selecting rep ranges first is frankly reverse engineering the situation.
It is this whimsical style of thinking that leads to this notion of “hypertrophy programs”, developed by simply taking Starting Strength and swapping out the sets of 5 for sets of 8. As though Mark Rippetoe had decided that he was going to build a beginner strength training program by taking a bodybuilding program and lowering the reps while leaving the rest untouched. This line of thinking also leads people to completely perform programs where a choice is left up to the user, such as Westside Barbell for Skinny Bastards or 5/3/1. When told that these are “strength programs”, the trainee in turn makes all the assistance work sets of 3-5, thinking that the sets of 8-20 reps that were there before must have been some sort of accident. In their minds, a program is simply a series of movements that coexist geographically on a piece of paper, and in no way do the movements harmonious exist for the purpose of supporting the goal of the program.
"I mean, I guess he was doing sets of low AND high reps"
Truth be told, when I develop a program, the rep ranges are almost an afterthought. After establishing the goal of the program and the frequency of training available, I move into determining which movements will be the most effective, select set number to manipulate volume, and plan rest periods around the goal of the movements within the program. Rep ranges are decided at the end, if even at all. I have written in a previous stream of consciousness that, in the future, when I design a program, I am considering only putting in the sets and leaving the rep range up to the user.
We need to understand that strength, size, endurance and power are always constantly being developed in our training, even if our training itself is not specifically conjugate in nature. Additionally, in understanding ourselves, we must learn that certain movement patterns may in fact necessitate that we employ unique rep ranges in order to achieve our own desired results. I personally have made much greater gains on my deadlift when I train in the 8-12 range versus the 1-5 range. When I trained 20 rep squats, my 20 rep max on squats went up steadily over 6 weeks, whereas my 5rm stayed practically the same. Am I to think that I stagnated in strength, or perhaps I should instead conclude that my strength at higher reps increased, whereas my strength at lower reps did not?
It necessitates being able to think of training with a very long view and broad perspective. One needs to understand the interplay of all of the pieces of a training program, and realize that progress is not a random accident brought about the instant that one does 6 curls instead of 5, but instead the result of balancing the equation at all ends. It requires soul searching and introspection as much as it requires science and research. Binding your results to the rule of rep ranges is to deny your ability to forge your own destiny through toil and sweat. If you do what it takes to make your lifts go up, whatever it takes, you will find that sometimes, sets of 8 will be more effective than sets of 5, and sometimes, to get in more reps, it means keeping the reps at 3 while jacking the sets up to 10 or 12. Let others worry about ensuring that they are avoiding training for endurance while you hammer out 20 rep squats. They can wonder “how” when you put on muscle, while you can simply wonder about “what next”.