The role of stretching in sports
1) biomechanics of stretching exercises
2) stretching as a way to prevent sports injuries
3) the effect of stretching exercises on athletic performance.
Stretching (stretching exercises) is a set of specific exercises that specifically prepare the working group of muscles for the main part of training or for competitions. The concept of plasticity, which is closely related to stretching, is traditionally considered as a constant ability of the working group of muscles to perform active work. The development of plasticity is an important element of physical fitness, and, accordingly, stretching of skeletal muscles to improve it is now very common in sports practice, not only among professional athletes, but also among participants of sports entertainment events. However, despite the extreme prevalence of stretching, the main purpose of which is to reduce the passive resistance of the musculoskeletal unit, reduce the risk of injury, and generally improve athletic performance, at the moment there is very little, and on some issues, there is no scientific data on the mechanisms of influence of stretching on the body. Until recently, much of the knowledge in this area was based on research conducted using goniometric technologies (a method for measuring angles formed by different parts of the body) and experimental models on animals. In recent years, a growing number of literature based on fundamental research of the physical and mechanical properties of the human musculoskeletal system.
The main questions in this area remain the same – how and to what extent stretching exercises affect the mechanical properties of the muscle-tendon unit, that is, how the muscle and its tendon become more plastic (less rigid) in the process of stretching. It is established that if the muscle during the so-called static stretching is at rest, then over time the effect of stretching due to the natural resistance of the muscle should come to naught. This phenomenon, called stress relaxation, clearly demonstrates the reaction of the muscle-tendon unit to such exercises. A number of scientists have studied the described phenomena on a human model. In particular, it was found that during the performance of five one-and-a-half-minute stretching exercises in a row, the resistance of the muscles and ligaments is consistently reduced, which in turn indicates the presence of at least a short-term effect of stretching (a few minutes). However, after an hour after the specified experiment, the detected effect disappears completely, and if the subjects perform three consecutive stretching exercises for 45 seconds each, the resistance of the muscles and ligaments remains the same as if the stretching was not performed at all. Based on these studies, scientists concluded that stretching exercises can affect the passive physical and mechanical properties of the muscle and tendon unit, while the effect achieved is extremely short-lived.
However, for a long time, it was possible that the effect of improving muscle plasticity could be maintained for a longer period of time. This crucial issue has been the subject of several studies. So, during four weeks, the subjects performed health – improving exercises for 9 thousand seconds, and a set of static exercises for 36 thousand seconds, and as a result, the resistance of muscles and ligaments in response to stretching remained the same. In other words, the view that the positive effect of stretching can be maintained for a long time, with one exception of one], was refuted experimentally. Despite these relatively new data, it is obvious that stretching before training helps to "warm up" the muscles and increase the working range of movements. This positive effect, scientists today can not be associated with any physical property, especially given the fact that the muscles and ligaments are gradually getting used to stretching loads. To solve this mystery, scientists suggest a closer study of the neural side of stretching.
Stretching as a way to prevent sports injuries
The practice of athletes using stretching to reduce the risk of injury has recently attracted the most attention of scientists, as evidenced by a number of recent scientific papers. In particular, the 2005 Shrier study analyzed the results of 293 papers on this topic, 14 of which involved experiments using a control group. Of these, in five studies, scientists concluded that stretching is an effective means of preventing sports injuries, in three studies it was found that it causes more harm than good, and in six more, no relationship between these phenomena was found. It should also be noted that in all studies that established positive dynamics from stretching classes, the possibility of active outside interference in the course of experiments was provided, so it is difficult to answer on their basis whether it is possible to reduce the risk of sports injuries by stretching yourself. The most popular work from the opposite point of view was conducted By Ekstrand, Gillquist, and Liljedahl, in which the authors described a specialized program they developed that includes
1) active adjustment of the training process
2) providing athletes with high-quality equipment
3) prevention of ankle sprain
4) the special rehabilitation program
5) preventing athletes with an untreated knee injury from training
6) regular conversations about the need to play in a disciplined manner, as well as about the harm that injuries bring not only to health, but also to a sports career
7) regular check-UPS by the doctor (s) and physiotherapist (s).
It should be noted that when implementing the described strategy, it is almost impossible to make an unambiguous conclusion about the contribution of each component to the overall positive effect.
Most experts question the practical value of other studies, due to the significant variety of technologies used in them, as well as the lack of a proper system of historical control. In three different studies, it was established that stretching exercises in many cases can increase the risk of injury, but their conclusions should be considered with a certain degree of caution, since these studies do not analyze many other causes that can lead to an athlete's injury. Six other studies did not reveal the possibility of preventing sports injuries through stretching. One of the most extensive studies by Pope et al. in 2000 involved 1,538 military personnel who were forced to perform certain work with and without stretching. The result has not been established that there is any relationship between the stretching and the risk of injury. In another study in 1993, van Mechelen and a group of colleagues observed the training of 421 athletes, and also did not find a similar relationship. However, it is worth noting that conducting such studies is very difficult: for the reliability of the data obtained, you need to observe a lot of subjects, which in most cases requires significant material costs, plus you need to keep in mind a number of factors, such as the presence of injuries in the past, and so on, which can also affect the final result. Nevertheless, despite the conclusions of the described works, it should be said that to date there are no reliable data that would allow us to say that stretching is an effective way to prevent sports injuries.
Influence of stretching exercises on sports results
The point of view that stretching helps not only reduce the risk of injury in athletes, but also contribute to their achievement of high sports results is very common. However, sports competitions themselves are extremely complex and multi-faceted,and cannot be accurately measured in the laboratory. You can only analyze some of their aspects, such as the maximum isometry, dynamic strength and endurance of athletes, the height of jumps, and so on.
There are a number of studies evaluating the degree of arbitrary muscle contractions ((1 RM, isometric and isokinetic contractions) or the height of jumps, as a criterion for determining the short-term effect of stretching exercises on athletic performance, which have shown that stretching reduces performance.
It is noteworthy that to date, there is no work that reliably proves the positive impact of this type of stretching on the competitive result, while many studies have revealed even a negative pattern. As a result, you can come to the unexpected conclusion that stretching before a performance reduces the maximum index of muscle activity, resulting in athletes showing worse results in such disciplines as, for example, high jumping. The facts obtained by scientists look very convincing, if we take into account the fact that they analyzed both the physical and mechanical and neural aspects of stretching exercises, and even though there are many questions about the biomechanics of such phenomena. As for running competitions, scientists have concluded that stretching also does not affect or negatively affects the speed of running.
Separately, scientists also studied the question of how regular stretching exercises affect athletic achievements. In this case, most scientists agree that regularly stretching the muscles, the athlete in most cases achieves higher results by increasing the rate of voluntary muscle contraction. To date, the mechanism of this phenomenon, as well as its practical applicability in the training process, remain poorly studied. Scientists have yet to determine the causes of the identified paradox, in which stretching exercises before a performance worsen the biomechanics of muscle contractions, while regular exercise – on the contrary, it improves.
Another area of work of scientists is currently the so-called issues of energy saving, that is, the search for ways to reduce energy consumption in any type of physical activity, in particular when moving. In this case, researchers should pay close attention to the skeletal and muscular flexibility of a person, since according to the generally accepted point of view, the less this flexibility, the more energy a person saves in movement. As a result, it turns out that regular stretching sessions for several weeks will ultimately only lead to an increase in the energy consumption of the athlete. In this aspect, to date, only one study has revealed small positive results from stretching, observed immediately after the complex of exercises.
Results
During static stretching, the muscles are in a state of tension relaxation, that is, the biomechanics of the muscle-tendon unit improves for a small period of time (a few minutes), but the achieved effect quickly fades away.
When stretching the working group of muscles, the stability of the ligaments to the load gradually increases, and changes in the biomechanics of the muscle-tendon unit also occur.
Currently, there are no reliable facts that would allow us to say that stretching before training reduces the risk of injury.
According to research, it is not possible to say that stretching before training or performing can increase muscle strength and, consequently, improve athletic performance. On the contrary, regular stretching increases the athlete's energy consumption.
