Its not uselsess, as a natural you get your hands on whatever supplement that works and make the best out of it. You dont NEED proteinpowder either, but you use it to maximize/optimize your gains - simple as that!
my personal theory regarding juicers and why they lose so much mass when going off, is because the mass isn't really mass.
we all know about sarcoplasmic vs myfibrillar hypertrophy, i feel like if you juice your brains out and just lift for moderate reps, well sure you're getting a lot of sarcoplasmic tissue but it's not permanent, you're not making the CNS and nerve adaptations so when you go off it just disappears....they body doesn't like massive growth in short periods of time it prefers homeostasis and SLOW adaptations.
although with new peptides being release like HIFs and VEGFs, and NGFs we could trick the body into making more solid muscle, basically like strength training in a vial, though you would still have the issue of the bones and tendons not strengthening. i know when they use electroshock stimulation on lab rats to grow muscle there is still the issue of tendons not strengthening. same with gear, that's why there's so many injuries, muscle and strength blows up but tendons stay the same. of course you can mitigate that with deca though.
sorry if im rambling the idea of "controlled evolution" so to speak is one of great interest to me.
