A good pro training program isn't about pumping as much iron as you can (though I'm sure Hurts does a lot of squats, those tush push plays . . . ).
It's designed around functional strength, so it should incorporate strength and flexibility and range of motion. It's not the 1950s anymore.
Genetics limits how much functional strength a player can add, but combined with skating coaching, you can add some speed and quickness over time. And lower body strength to anchor, and upper body strength to win puck battles.
Michkov is pretty stout, so it's not like he needs a makeover, just incremental improvements the next two years, he likes to play near the net so being able to anchor better and handle stick checking will make him even more dangerous.
One reason a lot of prospect lists use 23 as the cutoff age is that by that point a player is physically mature and has been in a pro training program for a few years. Improvement past that point usually comes from experience and a better understanding of the pro game.