Is correct…only do you have to recruit a motor unit/muscle fiber to make it grow, you must create enough fatigue and damage to it?
Only longer sets(1016RM for set) would cause more fatigue in the ST fibers, thus would stimulate them more. (???)
Slow Twitch fibers are not strong enough to continue to produce enough force to lift the heavy weight, when the fast twitch fibers are fatigued then the continuation of the exercise is impossible. However the slow twitch fibers were not fatigued (they are just not strong enough to allow you to continue the set) so they are not stimulated (or they are but to a small degree). (???)
Yes for the most part that seems to be true. Most of the growth seems to occur in MU’s that are fatigued. How much of a role muscle damage plays on muscle growth is not exactly known. It does seem to play a part in growth though.
As for what muscle fibers are recruited, that generally depends on the load lifted and the rate of the lift. A heavy load lifted or a light load lifted fast both recruit fast twitch MU’s. I think there is some debate about how much or to what extent slow twitch muscle fibers are recruited ih heavy or ballistic movements.
The biggest difference between fast twitch and slow twitch fibers is the contraction rate and the time to fatigue. Fast twitch MU’s contract at a much higher rate than slow twitch. How much tension each of the types of MU’s can generate in comparison with each other I believe is unknown. It may be possible that they are both capable of producing equal amount of force when the contraction speed is slow. Slow Twitch fibers do take much longer to fatigue.
But two situations where fast twitch muscles are recruited first is in the case of a strech reflex(plyometrics, possilby the full body vibration/Nemes devices) and EMS.
So if you are trying to focus on fast twitch MU hypertrophy, then use lower repetitions and more sets. Also possibly look into EMS. For Slow twitch(although why you would want to unless you are a distance guy) would work the opposite. High repetitions and the need for fewer sets.