How to do it

With a barbell on boxes of the desired height, take a grip just outside the legs. Lower your hips with the weight focused on the heels, back straight, head facing forward, chest up, with your shoulders just in front of the bar. This will be your starting position.
Begin the first pull by driving through the heels, extending your knees. Your back angle should stay the same, and your arms should remain straight. As the bar approaches the mid-thigh position, begin extending through the hips.
In a jumping motion, accelerate by extending the hips, knees, and ankles, using speed to move the bar upward. There should be no need to actively pull through the arms to accelerate the weight. At the end of the second pull, the body should be fully extended, leaning slightly back, with the arms still extended.
As full extension is achieved, transition into the third pull by aggressively shrugging and flexing the arms with the elbows up and out. At peak extension, pull yourself under the bar far enough that it can be racked onto the shoulders, rotating your elbows under the bar as you do so. The bar should be racked onto the protracted shoulders, lightly touching the throat with the hands relaxed.
Immediately recover by driving through the heels, keeping the torso upright and elbows up. Continue until you have risen to a standing position, and complete the repetition by returning the weight to the boxes.

Power Clean from Blocks

How to do it