If you use a light weight and lift it explosively you will recruit high threshold fast twitch fibers (IIB). The thing is, you can only do this for a short period of time before fatigue sets in, so you have to do a lot of low rep, light weight, explosive sets (like, 8x2-3). This is known as "Compensatory acceleration training" (CAT) and it's been popularized quite a bit by Westside barbell. They idea is to train your nervous systewm to recruit more fast twitch fibers so when you go to lift a maximum load you can lift more (the acceleration training doesn't actually stimulate the fibers, just recruit them).
Explosively as in as fast as you possibly can. For CAT you lower quickly as well.
For general lifting, explosive up, and slow/controlled down, about a 3-1-1 tempo.
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Complex problems have simple, easy to understand, wrong answers.