we use the vertec. I love it.
I guess Bailey´s Box Jump was 50 inches and not a “impulse” of 50 inches.
Voleyball players are the athletes that can jump higher than any other athlete ( because they need this for blockade and smashs ) so, even an elite volleyball player couldn´t jump 50"=1.25m.
BTW, i know that Pelé had a 32"=80cm impulse while he was a soccer player.
The biggest vertical I’ve heard in volleyball players is Hector Soto - reckoned to be around 48". Bear in mind, I can’t vouch for the accuracy of this figure. But from what I’ve read he has a spike height of 12’2".
I am doing on thesis on this topic, i cant answer your question at the moment however when i get some free time i’ll post some reseach on this topic. 
OK, Michael Wilson, who now plays for the Harlem GLobtrotters was the only one Ive ever heard of measuring a 50 inch vert. He can dunk a 12’3" hoop off of a straight jump up(he’s also 6’5" tall). I doubt Donovan had a vert like that, where did you hear it from?
Can you develop that? Or does it come naturally with different people?
Maximal speeds are assisted by stiffer legs which improves the rate of force development during ground contact. At high speed if the COM can deviate less downwards the support phase will be faster and Stride rating will be higher. Lathanen and Komi found that sprinters at 90-100% of max speed showed a less of a vertical drop of the COM on contact which allowed for better RFP on toe off.
Vertical plys can assist in developing shorter contact times and higher stride rates by increasing musculoskeletal stiffness in the lower limb.
Eur J Appl Physiol Occup Physiol. 1980;44(3):279-89.
Force-, power-, and elasticity-velocity relationships in walking, running, and jumping.
The following study also shows the relationship with maximal speeds and leg stiffness.
Leg power and hopping stiffness: relationship with sprint running performance.
Chelly SM, Denis C.
Laboratoire de Physiologie-GIP Exercice, Groupe PPeh, Faculte de Medecine, Saint Etienne, France.
PURPOSE: Although sprint performance undoubtedly involves muscle power, the stiffness of the leg also determines sprint performance while running at maximal velocity. Results that include both of these characteristics have not been directly obtained in previous studies on human runners. We have therefore studied the link between leg power, leg stiffness, and sprint performance. METHODS: The acceleration and maximal running velocity developed by 11 subjects (age 16 +/- 1) during a 40-m sprint were measured by radar. Their leg muscle volumes were estimated anthropometrically. Leg power was measured by an ergometric treadmill test and by a hopping test. Each subject executed a maximal sprint acceleration on the treadmill equipped with force and speed transducers, from which forward power was calculated. A hopping jump test was executed at 2 Hz on a force platform. Leg stiffness was calculated using the flight and contact times of the hopping test. RESULTS: The treadmill forward leg power was correlated with both the initial acceleration (r = 0.80, P < 0.01) and the maximal running velocity (r = 0.73, P < 0.05) during track sprinting. The leg stiffness calculated from hopping was significantly correlated with the maximal velocity but not with acceleration. CONCLUSION: Although muscle power is needed for acceleration and maintaining a maximal velocity in sprint performance, high leg stiffness may be needed for high running speed. The ability to produce a stiff rebound during the maximal running velocity could be explored by measuring the stiffness of a rebound during a vertical jump.
the mechanics of a vertical jump have different concerns as far as body proportions. I’ve also found that the vertical jump deals mainly with knee extension and little with hip extension.
In vertical jump, calves and quads are a big deal, in running jumps and sprinting, glutes and hams are more important than what they are in straight up vertical.
Goose I read a study in Strength & conditioning journal that showed the EMG analysis of the contributing muscles in the vertical jump. I found it interesting because the quad portion was less than 20% most came from the calves and then the hips. I will try to find the study and post it.
I was under the impression the calf/ankle were less than 15%. I thought the majority of the vertical leap came from the glutes and hams.
Well, first i was thinking like you, but then…
try to imagine a vertical leap without move your calves;
i mean, freeze your calves and try to jump as high as you can ?! Can you see now ?! how important are the calves in vertical leap ?
That has nothing to do with the importance of calves in the vertical jump. If you looked at it that way, you could say think about jumping without using your thighs. Does that mean hamstrings/quads are 100% of the vertical jump? No!
Bottom line, calves are extremely overrated especially in the vertical jump.
Of course thighs are important in vertical jump, much more than calves,
tooking me as an example;
i can jump without thighs about 8" or 20cm…
and about 20" or 50cm without calves…
Think of the quads as the Rocket, and the calves as the rocket boosters. The rocket can do the job without the boosters, but the boosters can’t do it without the rocket. The rocket would have to work harder, and might move slower, but it would eventually get off the ground. The boosters are there to make the job of the rocket easier.
When I first started working out all I did was push-ups, sit-ups, and calf raises. I did all of this before I went to sleep the summer before I went to high school. I could always jump but never had much of a vertical. I wasn’t strong or powerful enough. Looking back I noticed that I could only get up real high with a running start. It wasn’t until I started really lifting weights around my sophmore year that I noticed my vertical improving. And it just so happened that I was squatting more than just push ups and calf raises. So I added some quads to go with my calves by squatting. My hips also got stronger, and I learned on my own “how” to jump more efficiently. By now I was surpising all the guys at the b-ball courts by dunking on them when they thought they were gonna block my lay-up. 
None of that would have happened if I was thinking about which is more improtant. Realistically the quads, and hips do the most work, but the calves are just as important if you wanna be more efficient. You can’t get “toe-off” with out the calves. Weak calves will affect everything from your start to your finish.
We all know that one area is doing more work during some activities, but we should train the others like they’re equally important.
Calf raises with just your own bodyweight are not going to do much for anyone’s vertical leap so it is a bit of a mis-understanding to allmost dismiss calf importance over that. The irony being that people with weak calves are going to bend their knees more for the jump (other factors being leverage, RDF, type of jump ), so they are going to notice their thigh contribution much more.
According to my calculations Donvan does not get out with the field I have also noticed from video study he gets out very low, With that Trevor Grahm technique it looks like. So know Donovan does not have that 50+. You can see a great example of it on http://youtube.com/watch?v=t52HEOF6cwk he’s in lane 6 I believe. Look when the race really starts without Linford.
i was a personal trainer at his gym. he said he hit his head on the rim when he played ball when he was younger.
I read an article saying he could dunk from a standing jump. Though with his height/limb lengths this only means he at least jumps 28"+. I’m sure he could jump even higher but, 50"???