The eccentric phase, or landing phase, is one of three parts of a plyometric exercise. This phase involves the preloading of the agonist muscle group. During this phase, elastic energy is stored and muscle spindles are stimulated. An example of this is the portion of the squat jump from when the feet come into contact with the ground to the bottom of the movement (landing). The explosion out of the bottom of the movement into the jump is called the concentric phase. The time between is called the amortization phase. 
- McNeely/Sandler 2007, p.13.
- Baechle/Earle 2000, p.428.