Eccentric Definition Anatomy

With eccentric contraction, the external force on the muscle is greater than the force that the muscle can generate, so the elements of the elastic row are also forced to lengthen due to the high external load. This mechanical energy can be recovered during contraction, which provides a higher force. The model in Fig. 2.7 is a simplified explanation of why different types of muscle contraction produce different amounts of maximum force (Fig. 2.8). The pre-stretch phase is also known as the charging phase. During this phase, there is an increase in the activity of the muscle spindle. Three important factors need to be amplified: rate, magnitude and duration. The transition time between eccentric and concentric muscle contraction is called cushioning.32,33,34 This transition period is important because a longer rest period can reduce the potential energy generated during exercise. The last phase of a plyometric exercise is the shortening phase. A rapid concentric contraction that allows movement to become explosive.32,33,34 Interestingly, the intensity of DOMS is lower in the elderly than in young adults.

This is due to a decrease in range of motion in the elderly population and atrophy of rapidly contracting muscle fibers. For this reason, eccentric training to improve strength is recommended for the elderly. Isotonic contractions maintain constant tension in the muscle as the muscle changes length. Isotonic muscle contractions can be concentric or eccentric. The comparison of maximum force generation in concentric, isometric and eccentric contractions shows the following classification: eccentric > isometric > concentric. This classification can be explained by the muscle-tendon characteristics. There is another type of contraction in which the muscle lengthens as it contracts. This is called eccentric muscle contraction.

Eccentric contractions occur when a muscle counteracts a stronger force and reverses its initial trajectory. Eccentric contractions are sometimes called braking contractions, negative work or simply “negative”. Types of muscle contraction: Isotonic concentric contraction leads to muscle shortening, isotonic eccentric contraction leads to muscle lengthening. During an isometric contraction, the muscle is under tension, but does not shorten or lengthen. An eccentric contraction leads to the stretching of a muscle, while the muscle still generates strength; In fact, the resistance is greater than the force generated. Eccentric contractions can be both voluntary and involuntary. For example, a voluntary eccentric contraction would be the controlled lowering of the heavy weight increased during the above concentric contraction. An involuntary eccentric contraction can occur when a weight is too large for a muscle to carry, and is therefore slowly lowered under tension. Transverse cycling occurs even though sarcomas, muscle fibers and muscles lengthen and control muscle expansion.

Acute eccentric contraction (muscle contraction versus firm force with muscle extension) I shouldn`t be so eccentric with these people if they didn`t feed my sense of humor with their astonishment. Two situations can lead to an eccentric movement from this moment on; Occurs during eccentric muscle contraction (i.e. The muscle lengthens when it contracts, for example when lowering a weight) In both situations, the force generated by the muscle is not enough to keep the biceps brachii in a completely contracted state. This causes the vigorous lengthening of the muscle fibers, which is called eccentric contraction. The word “contraction” could be confusing because the biceps lengthen brachii, so what`s really going on? During an eccentric contraction, the muscle tries to shorten itself by creating tension, but it actually lengthens. Indeed, the external force exerted on the muscle overwhelms the force generated by the concentric contraction. Eccentric contraction is not a simple passive stretch of the muscle, but a tension stretch designed to slow down and smooth the repositioning of the heavy load. With eccentric contraction, a muscle resists the stretch load. The attached transverse bridges themselves are stretched, which increases the overall tension so that the force generated by the muscle is greater than the isometric strength of the muscle. The force that a muscle generates during eccentric contraction depends on the speed of extension, which depends on the size of the external load. The greater the external load (relative to the isometric strength of the muscle), the higher the elongation rate. The greater the elongation speed, the greater the effect of the stretching reflex, and therefore the greater the force generated by the muscle.

When the external force exceeds the maximum strength of the muscle, the muscle and its tendon are damaged. The relationship between muscle strength and the speed of shortening or lengthening is called the force-velocity relationship (Figure 6.18). Figure 6.19 shows the influence of the force-velocity relationship on the length-tension relationship of a muscle-tendon unit. The figure shows that at a certain length, the higher the shortening speed, the lower the stress and the greater the strain rate. Eccentric muscle contraction produces negative work. Negative work is the force used to reverse a muscle from its original trajectory. Since concentric contractions are the main means of muscle growth (and therefore called positive work), eccentric contractions are those that bring the muscle back to its starting point (negative work). Fig. 2.8.

Force-speed relationship. The force-speed curve of A.V. Hill shows that the speed at which a muscle changes length also affects the force it can generate. The shortening speed increases with the decreasing force, and therefore the increasing force leads to a decrease in the shortening speed. If the strength continues to increase, the muscle will not be able to shorten further; It contracts isometrically. If the external force on the muscle is greater than the force that the muscle can generate, the speed becomes negative in the case of eccentric muscle contraction. The origin of the terms concentric and eccentric is related to muscle contraction in fundamental physiology. As early as 1925, Hill defined 2 types of muscle contractions4: isometric (muscle length does not change during contraction) and isotonic. With this last contraction, the tension remains unchanged while the muscle length changes. There are 2 types of isotonic contractions: concentric and eccentric.5 With concentric contraction, muscle tension increases to meet resistance and then remains stable as the muscle shortens.