The mobility of joints depends on the state of training and on the stretching ability of different types of tissues. Sports and everyday movement activities are significantly influenced by this.
What is the stretching ability?
The mobility of joints depends on the state of training and on the stretching ability of different types of tissues. The term stretchability describes the ability of a tissue to respond to changes in length with resistance. Depending on the tissue composition, this ability varies greatly. On the musculoskeletal system, skin and internal organs, different structures are responsible for the stretching and expansion capabilities. Depending on function, these may include fascia, ligaments, muscles, tendons, joint capsules, or other related tissue types. The functionality of the connective tissue components is determined by the composition of the ground substance, which contains certain proportions of fibers and fluid substances. The quantitative ratio of these elements is genetically disposed and determines the viscoelastic properties and thus the extensibility of the tissue. A quantitative shift to the fluid side lowers resistance to stretching stimuli, while it increases when proportionally more fibers are present. Ligaments, with their relatively high proportion of collagen fibers, have low extensibility in the physiological state. The same applies to the outer layer of the joint capsule. Tendons and fasciae contain comparatively more elastic fibers, which allows a short-term increase in length when stretched, but this is quickly cancelled out by retraction forces. The length of a muscle itself can only be changed by contractions within a fixed range. The contractile elements are not elastic and therefore cannot be stretched.
Function and task
The totality of the extensibility of all types of tissues involved determines the mobility of the joints and the entire body. In movements in everyday life, but especially in sports, movement amplitude can have a major impact on movement quality and force development. In many sports, for example, the outswing movement is an important component for optimal force development at takeoff and maximum acceleration distance. Thus, the initial force comes not only from the active contraction of the muscles, but is also fed by the kinetic energy generated by the pre-stretching of the tendons, fasciae and joint capsules. The expression of both components is a determining performance factor. At the same time, it makes movement more effective because less active force development is required. The risk of injury is reduced because the acceleration is not transferred prematurely to the braking tissues or other joints and areas of the body. The same principle comes into play during breathing. During inhalation, the chest and lung tissue are stretched. At rest, the resulting retraction force is solely responsible for the return of the thorax during exhalation. Improvement of the stretching ability is achievable especially in childhood and adolescence through appropriate physical activities, since the connective tissue still contains relatively many elastic fibers. In adulthood, training for length gain is much more difficult because the tissue composition has changed. A short-term change in flexibility can always be achieved through stretching exercises, but long-term success can only be achieved through regular and adapted training. The type of stretching and the timing of its application play an important role in the effectiveness of these measures, especially in sports. Static stretching, also known as stretching, is still a very popular form of length training in sports, although findings in sports science have long proven that dynamic stretching is more effective. Any type of stretching prior to athletic activities that involve strength, speed, or quickness requirements is counterproductive. It has the effect of reducing performance because not as much kinetic energy is achieved through pre-stretching. A targeted warm-up is very important before endurance performances, while stretching exercises are not necessary. Also, the frequently still held opinion that regular stretching reduces the susceptibility of working muscles to injury has long since been scientifically refuted. However, it is important to carefully preheat the muscles through exercises.
Diseases and ailments
A whole series of diseases is the result of a process based on the change in tissue composition, which sometimes significantly limits the ability to stretch. Either a decrease in the amount of fluid in the ground substance or increased production of collagen fibers results in a shift in quantitative ratios. The collagen fibers move closer together and hydrogen bonds spontaneously form, making the tissue more cross-linked and less stretchable. For a certain time, this process is reversible, since the bridges can still be loosened, but later they can no longer be loosened, since fixed disulfide bridges lead to structural contractures of the muscle tissue, sometimes with considerable restrictions on movement. In the musculoskeletal system, such impairments occur as a result of immobilization in joints or general immobility. Fibroses of various types are also based on this process despite different causes. Pulmonary fibrosis, for example, is triggered by toxins to which affected individuals are exposed over a prolonged period. The slowly progressive restriction of the lung tissue’s ability to expand significantly impairs respiratory function. Dupuytren’s contracture is a fibromatosis whose cause has not yet been determined. As a result of the pathological processes, the connective tissue tendon plate of the palm becomes hardened and increasingly loses its stretching ability. As the disease progresses, the fingers connected to it, especially the ring and little fingers, are pulled toward the palm and become immobile. Capsular shrinkage that occurs after injury or surgery can also be explained by the process described. A special form of this disease is the so-called frozen shoulder (frozen shoulder), in which massive movement restrictions occur in the shoulder joint due to the enormously reduced stretching capacity of the joint capsule. The process is very resistant to any form of therapy. All injuries involving tissue destruction are repaired as part of the wound healing process. However, the resulting scar tissue is much less stretchable than healthy tissue. This is not a difficulty with small scars, but large scar areas, such as those that develop after burn injuries, can cause significant mobility deficits. Exercise activities have a major impact on the stretching ability of the various tissues. Many pediatricians and physical education teachers today complain that children and adolescents are significantly more immobile than in the past. This certainly has to do with changes in exercise and leisure time behavior. The resulting mobility deficits can either not be eliminated at all in adulthood or only with great effort.
