Edited by Doctor Marcello Serra
The word stretching is of Anglo-Saxon origin and means stretching, elongation. This term is frequently used in the world of sport and the gym, but its importance and real meaning are not always understood. Over the years, stretching has been the subject of numerous studies, around which theories and application techniques have been developed. Basically it is a type of activity aimed at muscle stretching, both for the purpose of injury prevention and recovery after training.
The first studies on stretching were born from the simple observation of the animal world and human behavior. In fact, it is enough to pay attention to the gestures of all of us as soon as we wake up: we stretch, that is, we stretch the muscles that, during the hours of rest, have "stiffened" and "shortened." It is therefore an "innate need to stretch to prepare the body for a new day.
Muscles can be likened to rubber bands that lengthen and shorten, but they cannot shorten much unless they have been tightened enough first. A striking example is the tennis player who, before the serve, "loads the shot", or rather stretches entire muscle chains, then contract them violently and hit the ball as hard as possible. This is why a stiff muscle becomes weak in the same way as an over-stretched muscle.
To better understand stretching, reminders of muscle anatomy and physiology are now needed.
Every striated muscle in the human body, at the macroscopic level, is made up of fibers, formed in turn by more myofibrils, which ultimately consist of protein myofilaments. The latter are of two types: actin (thinner) e myosin, are superimposed and flow reciprocally.
The functional unit of a skeletal muscle is the sarcomere, at the ends of which, the "Z lines", the actin filaments are attached. In the median part of the sarcomere we find the myosin filaments which, during contraction, drag the actin filaments thanks to "transverse bridges", thus bringing the Z lines closer together. of the Z lines from the center of the sarcomere, until there is almost more overlap between the actin and myosin filaments.
In the absence of overlapping of the myofibrils, if the lengthening were to persist or increase, as during certain stretching exercises, the tension would be discharged on the connective tissues of the muscle fibers and of the muscle in general: sarcoplasmic reticulum, sarcolemma and endomysium.
From a study by Dr. Goldspink conducted at the University of London it has been seen that, after long periods of muscular stretching, the physicist is able to synthesize new sarcomeres, so as to re-establish the "normal" superposition of the actin and myosin filaments inside each sarcomere. .
Numerous "sensors" are present in the muscles, tendons and joints, which are called proprioceptors and which behave according to precise physiological rules. Among these, are of interest for our discussion, i neuromuscular spindles they Golgi tendon organs.
The neuromuscular spindles are the most numerous proprioceptors within the striated muscles. They send information to the Central Nervous System concerning the degree of stretching of the muscle. This allows you to select the exact number of muscle fibers that must contract to overcome a given resistance. greater load means greater number of contracted muscle fibers.
Stretching: second part "
