Reading articles about fitness, we often come across such a term as “isotonic contraction”. Simply put, these are muscle contractions. In the article we will highlight their influence on endurance and increased human strength.
Isotonic contraction is a form of muscle tension characterized primarily by a change, both in muscle length and in the angle of the joint. Also known as dynamic compression, isotonic exercises usually involve rhythmic and repetitive movement of large muscle groups. This is the type of muscle tension most often used during strength training and cardiovascular exercises, which leads to an increase in muscle size, strength and endurance.
Other forms of muscle contraction include isometric contraction and auxoton contraction.
Isometric contraction, in which there is no change in the length of the muscles and no visible joint movement, occurs when muscle strength acts against a motionless object. Isometric training is sometimes used by athletes to overcome certain weak points in the dynamic range of motion of a particular muscle group or to prevent muscle atrophy during limb immobilization. Osoxonic compression, in which resistance increases as force is applied, is most often observed in the heart muscle.
During isotonic compression, there is a separate physiological response that is not observed during isometric contraction. Since intensively working muscles consume oxygen, the heart rate also increases. With the increase in heart rate, heart rate – the amount of blood pumped by each heart rate also becomes high. As isotonic contraction continues, there is a gradual increase in systolic blood pressure associated with stable or slightly reduced diastolic blood pressure.
Thus, isotonic compression imposes an increased volumetric load on the heart muscle. The heart adapts to the increased load, creating strength and endurance. This adaptation is known as the cardiac training effect and occurs most often in response to the requirements of dynamic exercise. Isometric exercise, on the other hand, usually leads to an increase in systolic and diastolic blood pressure, accompanied by a moderate increase in cardiac output without a significant increase in blood flow to the working muscles.
Isotonic compression can be divided into eccentric and concentric.
Concentric contraction occurs when the muscle strength is greater than the resistance force and the muscle contracts. Shortening of the muscle leads to a sharp decrease in the angle of the working joint. In resistance training, this is usually a phase of movement that moves against gravity – for example, part of the biceps bends when the elbow bends and the bar moves upwards.
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