The Three Phases of a Plyometric (Eccentric, Amortization, Concentric)

A plyometric repetition is broken into three sequential phases:

1. Eccentric (loading / pre-stretch) phase — the muscle-tendon unit lengthens under tension, e.g., the dip/landing of a jump. Elastic strain energy is stored and the muscle spindles are activated, setting up the stretch reflex.
2. Amortization (transition / coupling) phase — the time between the end of the eccentric phase and the start of the concentric phase. This is the most important phase: it must be as short as possible. A prolonged amortization lets stored elastic energy dissipate as heat and reduces the stretch-reflex contribution, turning the movement into an ordinary concentric action.
3. Concentric (unloading / push-off) phase — the muscle shortens explosively, releasing stored elastic energy plus the reflex-augmented contraction, producing more force than a concentric action alone.

Together these phases are the applied form of the stretch-shortening cycle. Coaching cues emphasize minimizing ground-contact (amortization) time — "stiff ankles," "off the ground fast," "quiet, quick feet" — for reactive/fast plyometrics.

• Three phases: eccentric (load/stretch) → amortization (transition) → concentric (push).
• Amortization is the key, time-sensitive phase; keep it as short as possible.
• A long amortization dissipates stored elastic energy and weakens the stretch reflex.
• The phases are the practical expression of the stretch-shortening cycle.

• stretch-shortening-cycle — the three phases enact the SSC.
• plyometrics-definition — phases define the plyometric rep.
• reactive-strength — short amortization = high reactive strength.
• eccentric-action — the loading phase.
• concentric-action — the explosive push-off phase.