Power Training and the Stretch Shortening Cycle (SSC)

Definition of Stretch Shortening Cycle (SSC)

• Occurs when the musculotendinous unit (muscle and tendon) is eccentrically loaded before a concentric contraction.
• Involves three phases: eccentric (loading), amortization (transition), and concentric (explosive action).

Phases of the Stretch Shortening Cycle

1. Eccentric Phase (Loading Phase)

• Purpose: Store energy in muscles and tendons and initiate the myotatic stretch reflex.
• Stretch reflex: Based on the muscle spindle, it provokes a concentric contraction automatically (monosynaptic reflex at the spine level).

2. Amortization Phase

• Time between eccentric loading and concentric explosion.
• Crucial for quick energy use; energy can dissipate as heat if prolonged.
• Also known as transition phase or coupling time.

3. Concentric Phase (Explosive Action)

• Execution of explosive movement using stored energy and stretch reflex.
• Results in more powerful outputs compared to not using SSC.

Importance of Rapid Eccentric Loading

• Higher rapid loading stores more energy in muscles and tendons.
• Vital for maximizing the stretch reflex.
• Requires short amortization phase for effective use.

Role of Eccentric and Isometric Strength

• Essential for effectively using the SSC in training.
• Rapid eccentric loading and efficient transition phases enhance training outcomes.

Practical Example: Counter Movement and Depth Jumps

• Counter Movement Jump: Uses SSC; involves rapid eccentric drop and explosive concentric jump.
• Depth Jumps:
  • More intense; involve dropping from a box (e.g., 20cm or 40cm) to provoke SSC.
  • Greater height potential due to gravity-induced acceleration.
  • Necessitates quick amortization phase; otherwise, benefits are lost.

Training Implications

• Overloading SSC is beneficial; however, quick transition time is crucial.
• Depth jumps are highly intense plyometrics and require adequate eccentric and isometric strength.
• If improperly performed (e.g., long amortization phase), may not yield desired training effects.

Conclusion

• SSC is integral to power training; effective use depends on managing the phases efficiently.
• Depth jumps, despite their potential, must be executed correctly to maximize benefits without energy loss.