By Dr. Marcello Serra
The word stretching is of Anglo-Saxon origin and means stretching, stretching. This term is frequently used in the world of sports 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 application theories and techniques have been developed. Basically it is a type of activity oriented to muscle stretching, both for the purpose of accident 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 sufficient to pay attention to the gestures of all of us as soon as we wake up: we stretch ourselves, that is we stretch the muscles that, during the hours of rest, have become "stiffened" and "shortened". It is therefore an innate need to stretch ourselves to prepare the body for a new day.
Muscles can be compared to elastics that stretch and shorten, but are not able to shorten much, unless they have been tense enough before. A striking example is the tennis player who, before the service, "loads the blow", or rather stretches whole muscle chains, to 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 excessively stretched muscle.
To better understand stretching, it is now necessary to recall muscle anatomy and physiology.
Each striated muscle of the human body, on a macroscopic level, is made up of fibers, formed in turn by several myofibrils, which ultimately consist of protein myofilaments . The latter are of two types: actin (thinner) and myosin, they overlap and flow against each other.
The functional unit of a skeletal muscle is the sarcomere, whose extremities, the "Z lines", are the actin filaments attached. In the middle part of the sarcomere we find the myosin filaments that, during the contraction, drag the actin filaments thanks to the "transversal bridges", thus approaching the Z lines. The eccentric or elongation phase occurs in reverse, that is with the removal of the Z lines from the center of the sarcomere, until there is almost no overlap between the actin and myosin filaments.
In the absence of overlap of the myofibrils, if the lengthening should persist or increase, as during certain stretching exercises, the tension would be discharged on the connective tissues of muscle fibers and muscle in general: sarcoplasmic reticulum, sarcolemma and endomysium.
From a study by dr. Goldspink, conducted at the University of London, showed that, after long periods of muscle stretching, the physicist is able to synthesize new sarcomeres, so as to re-establish the "normal" overlap of the actin and myosin filaments within each sarcomere .
Numerous "sensors" are present in the muscles, tendons and joints, which are called proprioceptors and behave according to precise physiological rules. Among these are of interest for our treatment, the neuromuscular spindles and the Golgi tendon organs .
The neuromuscular spindles are the most numerous proprioceptors within the striated muscles. They send information concerning the degree of muscle stretching to the Central Nervous System. This allows you to select the exact number of muscle fibers that must contract to overcome a given resistance. Therefore greater load means more number of contracted muscle fibers.
Stretching: second part »
