This is effective, but difficult weigthlifting exercise.
Stand up straight with your feet shoulder width apart.
Grab the barbell or dumbbells and keep them down on extended arms.
As you exhale, lift the bar from the floor by extending the hips and the knees forcefully.
At maximum plantar flexion, push bar from the shoulders.
Push the bar with the arms to a fully extended elbow position overhead.
Lower the bar to shoulders.
Flex hips and knees slightly as bar touches shoulders.
Straighten the hips and knees before the upward movement phase begins again.
This is a high risk exercise that can cause injury. Always start practicing it with light weights and under the supervision of experienced trainer.
Do not lean your torso back and do not arch your lower back.
Do not lift the bar using your legs or torso
Do not hold your breathe, it increases blood pressure.