There is an excellent article over on Elite FTS now that deals with isometric exercises for athletes.
Isometric Training for Athletes
Although the article begins, inexplicably, with a picture of barefoot running, it's not about running at all. Instead, it's about isometric exercises, often combined with explosive exercises.
The idea is pretty simple - you use the isometric exercise to get used to resisting force, and then acting to suddenly tense your muscles against that force to overcome it. Done properly, this totally eliminated the "stretch reflex," where your body stores energy in its elastic tendons briefly before using it to reverse a movement. Think of how you crouch down briefly before you jump, to coil up and store some energy.
The execution is pretty smart - he shows how to load the isometric and then perform unloaded explosive exercises, as well.
Overall, this is a great explanation of an excellent tool in a strength & conditioning coach's toolbox. Worth checking out if you are, or train, an athlete.