Stretch Shortening Cycle (SSC)

Stretch-shortening Cycle (SSC): The stretch-shortening cycle is a coordinated sequence of quick eccentric (lengthening/pre-stretch), amortization (transition), and concentric (shortening) muscle actions that result in greater power output than is achieved if a quick pre-stretch does not precede a concentric contraction. This mechanical and neuromuscular phenomenon is fundamental to explosive athletic performance (power ), such as jumping, sprinting, or throwing.

Stretch-shortening Cycle Steps (SSC):

1. The first step in the cycle is a rapid and forceful lengthening (eccentric), while electromyographic (EMG) activity increases. This increase in EMG activity likely occurs due to both voluntary recruitment and stimulation of stretch receptors and the stretch reflex .
2. This is followed by a brief isometric contraction (amortization phase), during which the EMG activity continues to increase. Muscle fibers maintain the same length, while tendons and fascia (connective tissue) continue to lengthen and store elastic energy.
3. Finally, a powerful concentric contraction occurs as both stretch reflex and voluntary recruitment result in a concentric contraction of the largest and fastest motor units. Further, this concentric contraction is combined with the elastic recoil of tendons and connective tissue, maximizing force output.

• Related Topics: Power , Plyometric Exercise , Stretch-shortening Cycle , Force-velocity Curve , Amortization Phase , Rate of Force Development , Counter-movement Jump (CMJ)

Related Courses:

• Power (High-velocity) Training: Introduction
• Lower Body Power Exercises
• Upper Body Power Exercises and Total Body Power Exercises

Frequently Asked Questions (FAQ):

What are the 3 phases of the stretch-shortening cycle (SSC)?

• They are the same phases that occur during exercise; however, they may be referred to by different names.

1. Eccentric: quick pre-stretch (loading) phase.
2. Amortization: isometric (coupling or time to rebound) phase.
3. Concentric: shortening (rebound) phase.

What does the stretch-shortening cycle do?

• A motion that includes an SSC results in significantly larger amounts of force, work, and power output during the shortening (concentric) phase than movements that do not include an SSC.

How long should the amortization phase last?

• Ideally, it should be as short as possible.

How can I improve my stretch-shortening cycle (SSC)?

• The first step to improving the stretch shortening cycle is to include progressive plyometric and power exercises in a regular resistance training program. Additionally, increasing maximal strength (especially during the amortization phase of a movement) in combination with power exercises can be very beneficial. Last, continue to perform power and plyometric exercises with the intent to decrease the duration of the amortization phase and increase speed/distance.

What is the stretch-shortening cycle during golf?

• The pre-stretch (eccentric phase) occurs during the backswing, the amortization phase would be the top of the swing, and the concentric phase would be the swing.

What is the stretch-shortening cycle during swimming?

• Assuming we are discussing the breast stroke, the pre-stretch (eccentric phase) would happen during the recovery, the amortization would be the transition between the recovery and pull phases, and the shortening (concentric phase) would be the pull phase.

Examples of the Stretch-Shortening Cycle (SSC) During Plyometric Exercises:

1. Box Jump: The descending phase would be the quick pre-stretch (eccentric phase), the ascending phase/jumping upward is the concentric phase, and the amortization phase occurs at the bottom when the athlete transitions from descending to ascending.​
2. Depth Jump: After stepping off a box, the landing is the quick pre-stretch, the concentric phase is jumping upward, and the amortization phase is the brief moment between landing (eccentric phase) and jumping upward (concentric phase).
3. Ice Skaters: After jumping laterally, the landing is the quick pre-stretch, the concentric phase is the push-off laterally to the opposite side, and the amortization phase is the instant between landing on one foot and pushing off laterally.
4. Medicine Ball Chest Pass: The backward movement that occurs during catching is the pre-stretch (eccentric loading), the concentric phase is the forward thrust (concentric phase) to pass the ball, and the amortization phase is the brief pause between the backward movement (eccentric loading) of the arms, and the foward passing of the ball.
5. Power Push-Ups: The pre-stretch is the quick lowering of the body (eccentric) phase. At the lowest point of the push-up, the amortization phase is the transition between lowering the body and the concentric phase, which is explosively pushing up (concentric).​
6. Power Chop Medicine Ball Smash: The upward movement/back swing is the quick pre-stretch (eccentric phase), the concentric phase is the downward throwing movement, and the amortization phase occurs at the end of the backswing, transitioning from the upward movement (eccentric) to the downward throwing movement.