Wolfgang Ritzdorf states that plyometrics are to reduce ground contact time and redirect momentum. I like to separate the to categories into power and stiffness. Yesterday we did stiffness hops with a walking speed and three hops per leg before alternating. I felt that that exercise stimulates stiffness and that quality can be expanded by faster speeds and higher forces only if the rate of contraction is high. By keeping the ankle joint loaded (pretension) and the knee and hip joint with minimal bend you can get a nice pogo without the body fatiguing. The human body is use to flight times and rates of contraction with gait, same leg hops tend to fatigue new athletes rapidly as their is no recovery stride, hence why we only do three in a row before switching. The great benefit of this exercise as well as many drills, is that stiffness is being trained from day one instead of waiting for speed work later. I often do specific plyos the phase before the speed work so the lower leg systems are prepared to handle the velocities and demands. Prancing exercises such as old school Prime Time Deion Sanders drills can prepare the body without mimicking actual biomechanics.