variations: The vertical jump test can also be performed using a specialized apparatus called the Vertec. The procedure when using the Vertec is very similar to as described above. Jump height can also be measured using a jump mat which measures the displacement of the hips. To be accurate, you must ensure the feet land back on the mat with legs nearly fully extended. Vertical jump height can also be measured using a timing mat. The vertical jump test is usually performed with a counter movement, where there is bending of the knees immediately prior to the jump. The test can also be performed as a squat jump, starting from the position of knees being bent. Other test variations are to perform the test with no arm movement (one hand on hip, the other raised above the head) to isolate the leg muscles and reduce the effect of variations in coordination of the arm movements. The test can also be performed off one leg, with a step into the jump, or with a run-up off two feet or one foot, depending on the relevance to the sport involved. For more details see vertical jump technique.
Less helpful was my early realization that I was a two-hand dunker, in light of my inability to palm a basketball on the move. It’s common knowledge among dunkers that throwing down with two hands is typically harder than with one; the former requires a higher vertical leap. So as I flailed haplessly at the rim last spring with one hand, I felt not just discouragement but also fear. Fear that I would miss big chunks of my kids’ ninth, sixth, and first years on earth just so I could come up embarrassingly short on a senseless goal that my wife and I would later estimate consumed 15 to 20 hours a week, on top of my normal work hours. And fear that I had shared this idea with my editors way too soon.
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Using only a lifting (concentric) phase for strength training exercises could also be more effective for improving vertical jump height than traditional, stretch-shortening cycle exercises under load, for two reasons. Firstly, using only a lifting phase involves faster rate of force development through higher rate coding, and this may increase high-velocity strength more over the long-term. Secondly, doing stretch-shortening cycle exercises under load *might* cause the tendons to increase stiffness to a greater extent. This would make the muscle lengthen more in the countermovement phase of a jump, and thereby reduce muscle force for a given countermovement depth.

After a one-week recovery period in January following Phase 1 of Jump Attack, Phase 2 brought an increase in intensity and time investment. This was the last stop before Phase 3, the wilderness where those attack depth jumps lived. (Attack depth jumps: Rest on your knees in front of a box; explode to your feet without using your hands; immediately jump onto the box; immediately jump as high as you can off the box, landing on the balls of your feet. Repeat. Many times. No blacking out allowed.) Phase 3 brought dramatic increases in both explosiveness and hip flexibility, two critical ingredients that I started to feel working in tandem. I emerged both confident and in dire need of another one-week recovery period, which I spent playing with our kids, watching dunk videos and mouthing the syllable Ow. Once healed, in early March, I returned to the rims with a friend whom I’d asked to toss lobs to me. There would be no more lifting. (After Jump Attack, what else could there possibly be?) From here on, I just jumped and recovered, jumped and recovered, attacking this tiny window of three or four weeks before my time away from the gym began to sap my strength. It would be over at that point, all over, whether I wanted it to be or not.

An important component of maximizing height in a vertical jump is attributed to the use of counter-movements of the legs and arm swings prior to take off, as both of these actions have been shown to significantly increase the body’s center of mass rise. 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 attributed to the stretch shortening cycle of the leg muscles enabling the muscles to create more contractile energy. 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 distally and posteriorly during the leg counter-movements, and powerfully thrusting the arms up and over the head as the leg extension phase begins. As the arms complete the swinging movement they pull up on the lower body causing the lower musculature to contract more rapidly, hence aiding in greater jump height.[5] Despite these increases due to technical adjustments, it appears as if optimizing both the force producing and elastic properties of the musculotendinous system in the lower limbs is largely determined by genetics and partially mutable through resistance exercise training.[6][7]