STARTING POSITION:
Select the appropriate plates amount to put them on the bar. Grab the bar with a prone grip with your hands at shoulder width apart. Separate your feet at hips width apart. Your knees should be bent to 90 degrees and your back should be parallel to the floor. Retract your shoulder blade. Contract your pelvic floor and core while keeping your chest up.
MOVEMENT:
Through the heels, move the bar upward by extending your hips and knees at the same time while you exhale. Continuing the pull, accelerate the barbell by extending your hips and shrugging your shoulders. Drop your hips into a squat position placing the barbell on your shoulders. Then extend your hips and knees. Now the bar should be just above your shoulders, under your chin. Helped by a push from your legs, drop the hips again into a lunge position and extend your arms to push the bar straight up. Slowly lower the weight until your hands are just above your shoulders. Return to the starting position lowering the bar at the same time you move your butt back as far as you can keeping the bar close to your legs.
TIPS: Make sure that you don't move your back and that you do the exercise with your hips and knees. Focus on stiffen the spine all the time using your core muscles.