Ground contact time displays the reversal strength and elastic ability one possesses in the lower limbs. Here is Chicago White Sox pitcher Hunter Speer demonstrating a depth jump with ankle weights adding an additional +22lbs. Even with this additional weight notice how his ground contact is extremely short in time.
Reactive strength (also referred to as reversal strength) is used during a fast transition between eccentric and concentric actions. The change in momentum during the lead leg block of a throw is an example of this ability being displayed on the field. Explosive Strength is the ability to exert maximal forces in little time. This ability is best displayed when achieving a maximal force as quickly as possible after an intense muscular stretch. Plyometrics, shock training and jumping with weight are great examples of means that develop explosive strength.
The lead leg block at front foot plant (FFP) shows how important reversal strength really is as the hamstring is forced to overcome the eccentric muscle action extremely fast. Although the lead leg blocks efficiency is largely based on the timing of pelvis rotation into FFP, training to improve the elastic qualities of the connective tissues and improve reversal strength should still be implemented. Hence why pitchers should be developing a surplus of explosive strength and reactive strength while also improving the elastic ability in their connective tissues.
Tendons have elastic qualities that aid in muscles producing power. I like to think of the tendons as springs rather than just the thing that connects the muscle to bone. Most coaches tend to focus on the actions of the muscle and ignore how the tendons assist powerful and explosive movements. This is why we employ plyometrics and shock training for our throwers upper and lower limbs.
Hopefully this article helps you realize the importance of understanding special strengths and what qualities a pitcher should be focused on building to an optimal surplus.