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Two foot jumpers spend a lot more time on the ground during take-off than one-foot jumpers. This allows them to generate a lot of force through the muscles of the calves, quads, glutes and hips. While one-foot jumpers rely heavily on elasticity and "bounciness", two-foot jumps are more reliant on strength and power. This is one of the reasons why football players are excellent two-foot jumpers - they have really strong lower bodies!
Like Todd and me, Nicholson was a two-foot jumper, and he echoed what Todd had told me was another flaw in my technique: “Your next-to-last step has to be a lot bigger. That big leap forward with your right foot—your penultimate step—that’s what allows you to explode off the ground.” To demonstrate, Nicholson sent me a video of Carter’s performance at the 2000 NBA Dunk Contest, which was a bit like showing a Monet to a finger painting kindergartner and saying, “No, like this.”
The amount of resistance a shock absorber develops depends on the speed of the suspension and the number and size of the orifices in the piston. All modern shock absorbers are velocity sensitive hydraulic damping devices - meaning the faster the suspension moves, the more resistance the shock absorber provides. Because of this feature, shock absorbers adjust to road conditions. As a result, shock absorbers reduce the rate of:
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.