Anyway that is not the point.
The complexities of that got me thinking. Exercise science is complicated. As you delve deeper into the biology of it all things get ever more complex. Metabolism and the cell biology is deep and difficult but also wonderful (check out this video) Muscle growth is driven by mechanical loading of the muscle, metabolic stress and muscle damage / trauma. The precise pathways get more and more complex the deeper you look.
However sometimes I wonder how much you need to understand. In the afterword to Art Devany's book Nassim Taleb talks about this idea - Evidence-based science and working with the black box. He explains that ultimately the science explaining the body keeps changing. What was once accepted wisdom changes as knowledge develops. Somtimes this change totally negates what has gone before.....yet while the explanation may switch 180 degrees, the experience is constant. Understanding the process is interesting but what is ultimately more important is applying what works.
For example if it is clear that negative reps work the lesson is to do negatives....how they work is a different issue. Whatever metabolic pathways they signal or whatever gene expression effects are apparent may be interesting.....but our suppositions about process may be totally wrong.
We are on a search for progress. Understanding the mechanisms may help but knowing what works is more important. So how do we find what works?
Here is Keith doing what works for him.....