Stretch shortening cycle
Encyclopedia
A stretch-shortening cycle (SSC) can be defined as an active stretch (eccentric contraction) of a muscle
followed by an immediate shortening (concentric contraction) of that same muscle.
structures in series with the contractile component can store energy like a spring
after being forcibly stretched . Since the length of the tendon
increases due to the active stretch phase, if the series elastic component acts as a spring, it would therefore be storing more potential energy
. This energy would be released as the tendon shortened. Thus, the recoil of the tendon during the shortening phase of the movement would result in a more efficient movement than one in which no energy had been stored . This research is further supported by Roberts et al..
However, other studies have found that removing portions of these series-elastic components (by way of tendon length reduction) had little effect on muscle performance .
Studies on turkeys have, nevertheless, shown that during SSC, a performance enhancement associated with elastic energy
storage still takes place but it is thought that the aponeurosis
could be a major source of energy storage
(Roleveld et al., 1994).
The contractile component itself has also been associated with the ability to increase contractile performance through muscle potentiation (Cavagna, 1977) while other studies have found that this ability is quite limited and unable to account for such enhancements (Lensel and Goubel, 1987, Lensel-Corbeil and Goubel, 1990; Ettema and Huijing, 1989).
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Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
followed by an immediate shortening (concentric contraction) of that same muscle.
Research Studies
The increased performance benefit associated with muscle contractions that take place during SSCs has been the focus of much research in order to determine the true nature of this enhancement. At present, there is some debate as to where and how this performance enhancement takes place. It has been postulated that elasticElasticity (physics)
In physics, elasticity is the physical property of a material that returns to its original shape after the stress that made it deform or distort is removed. The relative amount of deformation is called the strain....
structures in series with the contractile component can store energy like a spring
Spring (device)
A spring is an elastic object used to store mechanical energy. Springs are usually made out of spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication...
after being forcibly stretched . Since the length of the tendon
Tendon
A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...
increases due to the active stretch phase, if the series elastic component acts as a spring, it would therefore be storing more potential energy
Potential energy
In physics, potential energy is the energy stored in a body or in a system due to its position in a force field or due to its configuration. The SI unit of measure for energy and work is the Joule...
. This energy would be released as the tendon shortened. Thus, the recoil of the tendon during the shortening phase of the movement would result in a more efficient movement than one in which no energy had been stored . This research is further supported by Roberts et al..
However, other studies have found that removing portions of these series-elastic components (by way of tendon length reduction) had little effect on muscle performance .
Studies on turkeys have, nevertheless, shown that during SSC, a performance enhancement associated with elastic energy
Elastic energy
Elastic energy is the potential mechanical energy stored in the configuration of a material or physical system as work is performed to distort its volume or shape....
storage still takes place but it is thought that the aponeurosis
Aponeurosis
Aponeuroses are layers of flat broad tendons. They have a shiny, whitish-silvery color, are histologically similar to tendons, and are very sparingly supplied with blood vessels and nerves. When dissected, aponeuroses are papery, and peel off by sections...
could be a major source of energy storage
Energy storage
Energy storage is accomplished by devices or physical media that store some form of energy to perform some useful operation at a later time. A device that stores energy is sometimes called an accumulator....
(Roleveld et al., 1994).
The contractile component itself has also been associated with the ability to increase contractile performance through muscle potentiation (Cavagna, 1977) while other studies have found that this ability is quite limited and unable to account for such enhancements (Lensel and Goubel, 1987, Lensel-Corbeil and Goubel, 1990; Ettema and Huijing, 1989).
Community Agreement
The results of these often contradictory studies have been associated with improved efficiencies for human or animal movements such as counter-movement jumps and running (Asmussen and Bonde-Peterson, 1974b; Cavagna, 1977; Komi, 1984b). However the jury is still out as to why and how this enhancement takes place. It is one of the underlying mechanisms of plyometric trainingPlyometrics
Plyometrics is a type of exercise training designed to produce fast, powerful movements, and improve the functions of the nervous system, generally for the purpose of improving performance in sports. Plyometric exercises may also be referred to as explosive exercises...
.