Well generally speaking the first pull is just a controlled "deadlift" so you can safely omit that, but some people like me, can lift much more weight from the floor.
But in terms of pure explosion, the lifts from the hang have an edge. But as I said like me, I can't lift as much from the hang because my form changes. I just can't seem to get the power down. Some people are the opposite they lift more from the hang.
Plus with lifts from the hang you can invoke the stretch reflex with a dip, so that helps you athleticly.
Hmm I would do both. Since you have to take the bar from the floor anyway. Do the first one from the floor, and then the hang
In fact as you go higher it gets harder so you can do this -
power clean from floor first, then from mid thigh, then from above knee, below knee and then an inch from the floor. This way you get it all, and as you get tired, you go lower to compenstate
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