Any athlete who wants to maximize the height of their vertical jump should look to reduce their non-functional body weight (body fat) as much as possible. Though it's generally not recommended for youth athletes to go on a calorie-restricted diet, they should look to make healthy food choices. A good starting point for this is 40% of calories from carbohydrates, 30% from protein, and 30% from fats.
My warmup on March 29, following a day of recovery, left me feeling hoppier than I’d expected, and not nearly as achy. After 10 devastating near misses, and several others that weren’t as close, Jeff lofted the best lob I would see during this journey. I leaped, controlled it with one hand and—boodaloomp—in and out. I could have wept. “You got this!” Jeff implored. “You know you got this!”
Vertical jump training and assisted vertical jump training (essentially with a negative load) can each increase vertical jump height through increases in countermovement depth, even while actually reducing peak force produced in the jump. This seems to happen because the tendon becomes more compliant after these types of training, which means they elongate more during the countermovement phase of the jump.
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.