Among the methods applied in sport training, one that has been used more and more lately is stretching. The word, English in origin, is used as such in many other languages and it comes from the verb to stretch (meaning, in this sense, 'to make your arms, legs and body as straight as possible so that your muscles become long and tight'). More exactly, we talk about stretching the muscles, the joints, the tendons, the ligaments, etc.
Even before the term itself and the specific methods gained individuality, stretching was used a lot, especially in sports or activities which require a very good mobility of the joints and special muscle suppleness (gymnastics, martial arts, ballet, etc.). The positions specific to hatha yoga were a source of inspiration for the different movements practiced in stretching, but these positions underwent many transformations, adaptations and simplifications.
The most important effect of stretching is suppleness of muscles and joints, which enables increased effectiveness during the training. There are different opinions about the exact time when stretching should be introduced in the training program.
Thus, there are authors who support the idea that stretching is indicated for both warming up and relaxation, and even for the main part of the training. On the other hand, there is the opinion that stretching must be done only in the relaxation faze, because the movements that are specific to it induce a state of relaxation that you do not want at the beginning of the training. This state comes as a result of maintaining the passive faze of the positions.
Anyway, everybody agrees that stretching needs to be anticipated by general warming up, this way the practitioner will avoid tightening of the muscles.
General warming up takes about 5 minutes and it contains aerobic exercises. Stretching muscles that have not been warmed up might be dangerous for the integrity of the muscle fibers, which could rupture easily.
Both weight and resistance training should include stretching; the effectiveness will only increase once this type of movement is done during training.
Another reason for higher effectiveness is the fact that a bigger number of motive units are involved in the movement and they are mobilized faster once the volitional order is transmitted, through the motive impulse, to the muscles. Given the fact that the range of the movements is larger, the sportsman can cover bigger distances, larger scopes, saving, at the same time, energy, which is important especially in very demanding sports (athletics, canoeing, etc.).
You can have a whole training only with stretching exercises. However, this is not advisable: the muscles will quickly get used to only relax, without contracting, which can produce a certain misbalance.
Another possible negative effect of exaggerated stretching movements (over the physiological limit of a joint) is laxity of the joints or even accidents like sprains, dislocations, tightening of ligaments or tendons, etc.). The main joints (knee, shoulder, elbow, etc.) are protected not only by their own mobility, but also by the elasticity of the muscles which surround them (periarticular).
In conclusion, stretching must be accompanied by other forms of training so that the sportsman will have a complete and secure fitness program.