5 Types of Muscle Contractions
isometric: From or with muscle contraction against resistance, in which the length of the muscle remains the same. Isometric literally means «same length,» a condition that only occurs in a relaxed muscle. In fact, it is not the muscle length, but the joint angle that remains constant. Contraction means «shortening,» so isometric contraction, like all other forms of muscle contraction, involves internal movement processes that shorten muscle fibers. Unlike isometric activity, which occurs at a fixed joint angle, quasi-isometric activity can be performed over much of the entire range of motion. Therefore, its ripple effects, unlike those of true isometry, are not mainly produced near a certain joint angle. This quasi-isometric activity can be performed in concentric or eccentric mode (concentric quasi-isometry and eccentric quasi-isometry) and is highly relevant for training for maximum strength, muscle hypertrophy and active flexibility, rather than for maximum strength or speed. First of all, although it is indicated that the muscles lengthen in eccentric conditions, the muscles can only «contract» or «relax». I intentionally put the term «contract» in parentheses because today`s scientists believe that it is much more appropriate to refer to muscle action rather than muscle contraction. One of the reasons for this preference is that the active component of the muscle, the actin-myosin system, seems to behave like a sliding filament pattern in which the adjacent muscle filaments of actin and myosin slide together. Isometric muscle contractions. This type of contraction is used when your muscle remains in a single position and the attached joint does not move.
It does not provide a general strengthening of the muscle group. Instead, it strengthens your muscle for that unique and specific movement. An isometric muscle contraction is good for practicing the use of a muscle in a certain way after an injury. Eccentric muscle contractions also occur when you lower something heavy. Your muscle needs to stay tense to support the weight, but it lengthens to move the weight to another position. The process of muscle contraction is at the heart of all physical, strength and sports training, but there are many aspects of this seemingly well-known phenomenon that are not sufficiently understood, even on a more popular level. Unlike isotonic contractions, isometric contractions generate strength without changing the length of the muscle, which is common in the muscles of the hand and forearm responsible for grip. In the example above, the muscle contraction required to grasp but not move a heavy object before lifting it would be isometric. Isometric contractions are often used to maintain posture.
Eccentric contractions. This type of contraction occurs when your muscle is actively elongated during normal activity. An example of this is walking because your quadriceps muscles are active when your heel touches the ground and your knee bends or straightens into the crotch. concentric: (Of a movement), in the direction of the contraction of a muscle. (Z.B. Extension of the forearm on the elbow joint in case of contraction of the triceps and other extensor muscles of the elbow. Isometric contractions are sometimes described as yielding or overcoming. Play with identifying muscle contractions in your own body. As you move through your day, think about the muscular actions needed to accomplish the tasks you do. Which muscles make isotonic concentric contractions? Which muscles make isotonic eccentric contractions? Are there also muscles that perform isometric contractions in the same action? Traditionally, the following types of muscle contractions are defined, starting with the prefix «-iso» (meaning «equal»): isotonic (constant muscle tension), isometric (constant muscle length), isokinetic (constant movement speed) and isoinertial (constant load). The resistance offered by these devices increases in response to the increase in force generated by the muscles, limiting the speed of movement over part of their range to approximately isokinetic conditions. They are designed in this way, as some authorities claim that strength is best developed when muscle tension is maintained at a maximum at each point in the range, a statement that is neither proven nor generally accepted in relation to all types of force.
More advanced functional and unconventional training techniques such as fighting ropes, kettlebells, tires, hammers, bodyweight suspension devices, and sleds have become increasingly popular among the sports population.32 These different types of exercises require more skill, technique, mechanics, and coordination than traditional rehabilitation exercises. Unconventional exercises initiate the desire to perform in athletes and provide a positive mental boost. Overcoming contraction occurs when a muscle contraction is opposed by a motionless object, such as .B. the contraction created in the muscles when pressed against a wall. Fig. 2.6. Molecular mechanism of muscle contraction. The action potential moves through the transverse tubular system and the sarcoplasmic reticulum, which leads to the release of Ca ions. Ca ions bind to troponin C, resulting in conformational changes that allow myosin to bind to actin, resulting in muscle contraction. During each actin-myosin bond, the protein filaments slide towards each other to create a contraction that requires ATP.
With concentric contraction, the force generated by the muscle is less than the maximum of the muscle and the muscle begins to shorten. This type of contraction is widely known as muscle contraction. It requires more energy compared to the other two types, but this contraction produces the least force. Their muscles contain fiber called myosin. Depending on how you need to use your muscles, myosin fibers tighten and shorten or relax and expand. Myosin is also responsible for muscle contractions such as your heart rate, which occurs at regular intervals. With a longer action, the voltage fluctuates irregularly over a range of values. When the load is almost maximum, the muscles cannot maintain the same static muscle tension for more than a few seconds and the situation quickly becomes anisotonic isometric.
In general, the term should be isotonic reserved for short and severely restricted movement situations in which muscle tension certainly remains fairly constant. This method combines isometric and concentric contractions. At the beginning of the exercises, there is an isometric contraction of 3-5 s to increase muscle tension; at a given articular angle, the contractile elements contract and lengthen the elastic elements, so that the muscle contracts at high speed during contraction. Several motor units are recruited in this way, so this type of exercise improves neuromuscular coordination. Fast fibers are tiring, so this type of exercise prefers low repetitions and enough rest between sets. To perform these exercises, it is necessary to have a training partner or a special machine, since isometric contractions must be performed at or close to a maximum intensity. Therefore, it is recommended for professional athletes. With eccentric contraction, the external force on the muscle is greater than the force that the muscle can generate, so the muscle is forced to lengthen due to the high external load. The maximum force generated by the muscle is the highest; however, energy consumption is the lowest.
Fig. 2.8. Force-speed relationship. A.V. Hill`s force-speed curve 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 cannot 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. Because concentric contractions shorten, they are useful for speeding up one part of the body over another, including the parts loaded with external objects.
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