"ROM must decrease as muscles fatigue."
Interesting quote from Everett Aaberg, author of Muscle Mechanics. It may be an underlooked point because, well, the conventional advice is to terminate set when ROM decreases. Or, perhaps more frequently, the trainee begins to use more and more body english to maintain ROM.
Yesterday I experimented with the concept. Did a set of pullups. Tempo was deliberate, probably three seconds up, three seconds down. Slow as my reps were, I found that I wasn't going to reach chin level, at top, on my sixth rep. So, rather than using any body english, I simply pulled as high as I could (and still maintain tension in the lats). By rep 11 or 12 I was barely able to rise inches from the bottom position. I terminated the set when I could no longer move period. And I suppose that, had I wanted to, I could have continued to hang ... until I couldn't.
My finding was that, as ROM diminished, even markedly so, I found that I was able to maintain constant tension on the relevant muscles BECAUSE I allowed ROM to decrease.
Now, sure, with this kind of intensity, now we're talking HIT, one set will do ya. But perhaps there is a middle ground that allows for more subtle decreases in ROM AS ONE ACHIEVES A PREDETERMINED REPS GOAL.
I suspect that this is what bodybuilders do, as they seem to be the leading experts on the sort of 'mind-muscle connection' required to maintain muscle tension, which is a priority for them.