equation (h = g × t2/2), the computer can calculate their vertical jump based on the time in the air. 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 their 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. Maximising jump height An important element in maximising vertical jump height is an immediately preceding crouching action which preloads the muscles. This crouching action is usually performed quickly and referred to as a counter-movement: the rapid bending of the legs and the movement of the arms to the person's sides constitute the counter-movement to the actual jumps range of movement. The counter-movement and the jump collectively are referred to as a counter-movement jump (CMJ). The counter-movement of the legs, a quick bend of the knees which lowers the center of mass prior to springing upwards, has been shown to improve jump height by 12% compared to jumping without the counter-movement. This is standardly attributed to the stretch shortening cycle (SSC) e.g. the stretch of the muscles which occurs during the crouch generates a greater potential for the muscles to contract in the subsequent jump, which allows the jump to be performed more powerfully. Furthermore, jump height can be increased another 10% by executing arm swings during the take off phase of the jump compared to if no arm swings are utilized. This involves lowering the arms to the sides during the legs' counter-movements, and powerfully thrusting them up and over the head during the jump. However, despite these increases due to technical adjustments, some researchers consider that optimizing both the force producing and elastic properties of the musculotendinous system in the lower limbs is largely determined by genetics, and only partially mutable through resistance exercise training. Another method for improving vertical jump height