PED213A Stretch-Shortening Cycle PDF

PE D2 1 3 A: TCH - S H O RT E N I N G ST R E CYCLE  Objectives Enumerate and explain the 3 phases of stretch-shortening cycle What is STRETCH-SHORTENING CYCLE (SSC)? The basic muscle function is defined as the stretch-shortening cyc...

PE D2 1 3 A: TCH - S H O RT E N I N G ST R E CYCLE  Objectives Enumerate and explain the 3 phases of stretch-shortening cycle What is STRETCH-SHORTENING CYCLE (SSC)? The basic muscle function is defined as the stretch-shortening cycle (SSC), where the preactivated muscle is first stretched and then followed by the shortening action (Nicol et al., 2006). What is STRETCH-SHORTENING CYCLE (SSC)? It refers to the ‘pre-stretch’ or ‘countermovement’ action that is commonly observed during typical human movements such as jumping. This pre-stretch allows the athlete to produce more force and move quicker.  Athletes have been shown to jump 2-4 cm higher during the countermovement jump (CMJ) than they can during the squat jump (SJ) -Bobbert & Cashius, 2005 The action of the SSC is perhaps best described as a spring-like mechanism, whereby compressing the coil causes it to rebound and therefore jump off a surface or in a different direction (Figure 2).  Increasing the speed at which the coil is compressed or how hard it is pressed down (amount of force applied) will result in the spring jumping higher or farther. This is known as the ‘rate of loading’, and increasing this will often mean the spring will jump higher or farther. Therefore, a jump that incorporates a ‘run-up’ will often allow an athlete to jump higher or farther than a jump from a static position because of an increase in the rate of loading The SSC does not only occur during single-bout jumping or rebounding movements but also during any form of human movement when a limb changes direction. For example, during walking, jumping, running, twisting or even lowering and then raising your arm. As the limbs are continuously changing direction, there is constant use of the SSC in order to change the direction the limb is moving. The importance of the SSC in sport is evident. Nearly every movement that occurs involves some level of pre-stretch and usage of the SSC. So, naturally as a coach it is very enticing to find a way to optimize this mechanism.  3 PHASES OF THE STRETCH SHORTENING CYCLE 3 PHASES OF THE STRETCH SHORTENING CYCLE 1.eccentric 2.amortization 3.concentric Eccentric Phase This is when a muscle is actively lengthening under tension. During this phase, the muscle and its associated tendons are stretched, which stores elastic energy. This phase is crucial because it prepares the muscle-tendon unit for a powerful contraction by stretching the muscle fibers and increasing the tension within the tendons. Eccentric Phase This is the initial phase where the muscle is actively lengthening under tension. For example, during a sprint, this phase occurs when the muscles are stretched as the body prepares to push off the ground. This phase stores elastic potential energy in the muscle-tendon unit. Amortization Phase The transition period, where a time delay between loading the tendons with energy to the pre-burst of force generated. for instance; the end of the eccentric contraction of the quadriceps squat loading phase and just before the spring up to jump. Amortization Phase The amortization phase in the (SSC) is the brief period between the end of the eccentric phase and the beginning of the concentric phase. It represents the transition between the muscle lengthening (eccentric phase) and muscle shortening (concentric phase). Concentric Phase The concentric contraction from the same muscle lengthened in phase one. Unleashing the generated energy. For example, the quadricep concentric contraction, causing a powerful knee extension (as part of the triple extension of hip, knee and ankle into a jump). Concentric This is where the muscle actively shortens to generate force. This phase follows the eccentric (stretch) phase and the amortization (transition) phase. Concentric The muscle generates force through shortening, using the elastic energy stored during the eccentric phase to produce powerful movements. The effectiveness of this phase is closely tied to how well the previous phases are managed. Conclusion The stretch-shortening cycle (SSC) refers to the muscle action when active muscle lengthening is immediately followed by active muscle shortening. This combination of eccentric and concentric contractions is one the most common type of muscle action during locomotion. ACTIVITY Choose one (1) skill in your preferred sport. Analyze the muscles involved in that movement and how the 3 Stages of the stretch-shortening cycle was applied.