Recruitment of fibers also varies with the threshold of resistance. You can't do a max effort movement and primarily use slow-twitch fibers exclusively or even primarily .The speed of movement of a powerlifter is a consequence of the resistance being overcome, not of training deliberately slow(like for example, a bodybuilder trying to maximize time under tension). Rate of force development is different from maximum force output, but it's not a function of slow vs fast twitch recruitment.
