Just a quick 'thought' of the day type thing - there are always going to be people that are faster or stronger than you and people that are looking at you thinking you're faster and stronger than them. Another way of looking at it is that there are always things we can do to be faster and stronger - this applies to the weekend warrior and the pro athlete alike. It all comes back to the decisions we make - the sum total of them, not just the surface level training ones.
And sum totals are tricky. Any attempt to look at 'sum totals' in a really deep and meaningful way quickly runs into problems - our training is interconnected with things at a level of complexity that isn't easily investigated. Yeah, we can treat it with broad brush strokes - train more and get fitter, train harder and get fitter - and have some type of broad control over the outcome, but in a limited scope. It's analogous to what Michael Pollan discussed in one of his many books about nutrition - we like to make up simple equations (simple relationships) because they are the ones we can understand - not necessarily because they work or have a high degree of truth to them.
Sure, the body responds physiologically to stress. And diet. And a whole host of other things. But the details are so nuanced and beyond the edges of our understanding that i'd guess our ideas of how to maximize our performance/health/well-being today might not clearly resemble our ideas of how to maximize these things in the next century.
So the point(s) (if there are any) are that although we might as well work with what we have (our 'best guesses' at present) when pursuing our fitness goals, the science should be viewed with a critical eye and an understanding of the semi-paradox that what accounts for truth today might be lies tomorrow. And sweeter still is the notion that there are no ends to the fitness continuum - there is no top and bottom. There's only middle - and we're all right there in it together.