I don't know the reason - I don't think copper is a factor.
I'm sure you're right about supplements, but I do add 'naturally-occurring' foods/ herbs etc to address issues like muscle soreness. Pumpkin Seed oil and Saw Palmetto do seem to have corrected mild hair thinning, and quickly too
Perhaps just lucky with genetics, as a factor.
Speculating, (near) daily saunas and Tabata help.
I used to take cold baths, but UK weather (and mains water) is increasingly temperate. The body copes far better with cold than heat too - so sauna is a great stressor - and I stay in the sauna until it is unbearable ( which I treat as a fun challenge)
Also, with Tabata - I ensure I perform to the same level as when I started 10 years ago. So absolutely flat out to near exhaustion. The great think with this protocol is that I am fully in control for safety; it's quick and over fast, so not tedious; and I can ensure sufficient rest (on a 10 day cycle). Structure and monitoring
I use a Gym Boss timer on a cross trainer to get the 8 cycles of 20 second of full-out exercise with 10 seconds breaks
Anyway, I rely on very subjective feedback - your far more scientific and considered approach is a huge contribution.
Extraordinary that hormesis does not get more attention given the contribution to health. I hope you are writing a book!
My interest arose from martial arts training. We trained intensively for 3-minute bouts. After training and in between I felt fantastic. After stopping the martial arts (back injury), I missed and tried to recapture that feeling, trying interval sprints, cold baths and other methods - and then started to read to 'systemitise', when I stumbled on hormesis.
I believe in the Yin-Yang as a big contributing factor too - mobilising the parasympathetic system reinforces the contrasting hormetic effect. For 20 minutes each day I use a bi-aural download, with a mix of exercises including the Sedonna method, autogenics and Eckhart Tolle