A stretch-shortening cycle (SSC) is an active stretch (
eccentric contraction
Muscle contraction is the activation of tension-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as ...
) of a
muscle
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...
followed by an immediate shortening (
concentric contraction
Muscle contraction is the activation of tension-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as ...
) 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
elastic
Elastic is a word often used to describe or identify certain types of elastomer, elastic used in garments or stretchable fabrics.
Elastic may also refer to:
Alternative name
* Rubber band, ring-shaped band of rubber used to hold objects togeth ...
structures in series with the contractile component can store energy like a
spring
Spring(s) may refer to:
Common uses
* Spring (season)
Spring, also known as springtime, is one of the four temperate seasons, succeeding winter and preceding summer. There are various technical definitions of spring, but local usage of ...
after being forcibly stretched. Since the length of the
tendon
A tendon or sinew is a tough, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability ...
increases due to the active stretch phase, if the series elastic component acts as a spring, it would therefore be storing more
potential energy
In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors.
Common types of potential energy include the gravitational potentia ...
. 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 is the mechanical potential energy stored in the configuration of a material or physical system as it is subjected to elastic deformation by work performed upon it. Elastic energy occurs when objects are impermanently compressed, ...
storage still takes place but it is thought that the
aponeurosis
An aponeurosis (; plural: ''aponeuroses'') is a type or a variant of the deep fascia, in the form of a sheet of pearly-white fibrous tissue that attaches sheet-like muscles needing a wide area of attachment. Their primary function is to join musc ...
could be a major source of
energy storage
Energy storage is the capture of energy produced at one time for use at a later time to reduce imbalances between energy demand and energy production.
A device that stores energy is generally called an accumulator or battery.
Energy comes in ...
(Roleveld et al., 1994).
The contractile component itself has also been associated with the ability to increase contractile performance through muscle potentiation
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.
[{{Cite journal, last=Cavagna, first=Giovanni A., date=1977, title=Storage and utilization of elastic energy in skeletal muscle, url=https://journals.lww.com/acsm-essr/Citation/1977/00050/STORAGE_AND_UTILIZATION_OF_ELASTIC_ENERGY_IN.4.aspx, journal=Exercise and Sport Sciences Reviews, volume=5, issue=1, pages=89–130, doi=10.1249/00003677-197700050-00004, pmid=99306, s2cid=33617675] However it is still not established why and how this enhancement takes place. It is one of the underlying mechanisms of
plyometric training.
See also
*
plyometrics
Plyometrics, also known as jump training or plyos, are exercises in which muscles exert maximum force in short intervals of time, with the goal of increasing power (speed-strength). This training focuses on learning to move from a muscle extensi ...
References
Exercise physiology