Technique Tip: Determining how far out in front of you to place your front foot may require some trial and error. At the bottom of the motion, your front knee should be somewhere above your heel to mid foot. If your knee is behind your heel, your foot is too far forward; if it’s out over your toes, step out further. One trick to find the right distance is to start in the bottom position and adjust your stance from there. Then stand up and have someone hand you the dumbbells.
A second, more efficient and correct method is to use an infrared laser placed at ground level. When an athlete jumps and breaks the plane of the laser with his/her hand, the height at which this occurs is measured. Devices based on United States Patent 5031903, "A vertical jump testing device comprising a plurality of vertically arranged measuring elements each pivotally mounted..." are also common. These devices are used at the highest levels of collegiate and professional performance testing. They are composed of several (roughly 70) 14-inch prongs placed 0.5 inches apart vertically. An athlete will then leap vertically (no running start or step) and make contact with the retractable prongs to mark their leaping ability. This device is used each year at the NFL scouting combine.