Dynamometry is the measurement of muscle strength. The tension developed by one or another muscle group is a functional characteristic of the motor analyzer and is considered as an indicator of general physical development. In the study of the strength of muscle tension, indicators of the strength of the arms, legs, fingers and back strength (i.e., the strength of the muscles that extend the body in hip joints), etc. In psychophysiology, the measurement of hand strength and back strength is most often used. The study of endurance under static muscle tension is of particular interest due to the fact that it is present in any muscular activity and occupies a rather large place in it. To assess static muscle endurance, a special version of the dynamometric technique is used. In the process of measuring the strength of muscle tension, the coefficient of asymmetry (KA) is calculated. IN general form its value is determined by the following formula:
Where Vn - Index right hand, kg; Vn - indicator of the left hand, kg.
In practice, the method of determining muscle strength brushes are used as a test to establish the level of general physical development person. For this purpose, the muscle strength of both hands is measured before and after work. Comparison of the ratio of muscle strength of the right and left hands before and after the workload indicates a change in the involvement of bilateral regulation in the human body under the influence of the load.
CHAPTER2. METHODS RESEARCH PSYCHOMOTOR ORGANIZATIONS
Average statistical indicators of strength (in kilograms) of hands and back strength for student age group are given in table. 2.16.
Table 2.16. Average statistical indicators of hand strength and back strength for the student age group, kg
To measure the muscle strength of the arms and the dead strength, a hand-held knee dynamometer and a knee dynamometer are used. When measuring, it is necessary to comply with a number of conditions and, above all, the constancy of the posture of the subject. When measuring hand strength, the subject sits on a chair; the arm for which measurements are taken is extended forward, bent in elbow joint; free hand on knee.
Instruction. Squeeze the dynamometer spring as hard as you can by hand.
Measurements are repeated 3 times for the right and left hands, both before and after the load. After that, measure backbone also before and after exercise.
Instruction. Stand on the lower jaws of the dynamometer. Using a chain, adjust the dynamometer by yourself, i.e. in such a way that the measuring part of the device is at the level of your kneecaps. Grasping the upper branches with both hands, pull them up as much as possible, while unbending the torso.
Then the subject performs 20 squats, after which the experimenter measures the strength of each arm 3 times, and measures the back strength once.
The processing of the results is as follows:
1) calculate the average values (M) of the strength of the right and left hands;
2) calculate the coefficient of asymmetry (KA) for arm strength using the formula:
Analyzing the obtained data, compare them with the average values.
In table. 2.17-2.19 shows the age standards for muscle strength indicators published by various authors.
Table 2.17. The strength of the hands of adolescents 14-17 years old
METHODS FOR STUDYING PSYCHOMOTORICS IN COMPREHENSIVE HUMAN STUDY
|
38 and over |
59 and over |
Note. Data obtained by N. A. Grishchenko.
Table 2.18. Dynamometry of the right hand (in kilograms), averages
|
Ast, Years | ||
Note. Data presented by Rudik.
Table 2.19. Age-related changes in manual strength in men and women
|
Age, Years |
Quantity |
The strength of the right |
The strength of the left |
Quantity |
The strength of the right |
The strength of the left |
|
test subjects |
Hands |
Hands |
test subjects | |||
CHAPTER 2. METHODS RESEARCH PSYCHOMOTOR ORGANIZATIONS
The end of the table. 2.19
|
Age, Years |
Quantity |
The strength of the right |
The strength of the left |
Quantity |
The strength of the right |
The strength of the left |
|
test subjects |
test subjects | |||||
|
51 and older |
Note. Data presented by E.P. Ilyin.
IN under conditions of isometric contraction, the muscles exhibit maximum static strength.
Maximum static strength and maximum voluntary static muscle strength
AND an isometrically contracting muscle develops the maximum possible tension for it while simultaneously fulfilling the following three conditions:
activation of all motor units (muscle fibers) of a given muscle;
full tetanus mode in all its motor units;
muscle contraction at rest length.
IN this case isometric tension muscle corresponds to its maximum static strength.
M the maximum force (MS) developed by a muscle depends on the number of muscle fibers that make up a given muscle, and on their thickness. The number and thickness of the fibers determine the thickness of the muscle as a whole, or, in other words, the cross-sectional area of \u200b\u200bthe muscle (anatomical diameter). The ratio of the MS of a muscle to its anatomical diameter is called the relative strength of the muscle. It is measured in newtons or kilograms of force per 1 cm2 (N/cm2 or kg/cm2).
A the anatomical diameter is defined as the area of a transverse section of a muscle, drawn perpendicular to its length. A transverse section of a muscle, drawn perpendicular to the course of its fibers, makes it possible to obtain the physiological diameter of the muscle. For muscles with a parallel course of fibers, the physiological diameter coincides with the anatomical one. The ratio of the MS of a muscle to its physiological diameter is called the absolute strength of the muscle. It fluctuates within 0.5-1 N/cm2.
AND The measurement of muscle strength in a person is carried out with it. arbitrary effort, the desire to minimize the necessary muscles. Therefore, when they talk about muscle strength in humans, we are talking about maximum arbitrary strength (MPS, in sports pedagogy, this concept is equivalent to the concept of "absolute muscle strength"). It depends on two groups of factors: muscular (peripheral) and coordination (central nervous).
TO Muscular (peripheral) factors that determine MPS include:
mechanical conditions for the action of muscle traction - the shoulder of the lever of action of muscle force and the angle of application of this force to the bone levers;
muscle length, since muscle tension depends on its length;
the diameter (thickness) of activated muscles, since, other things being equal, the manifested muscle strength is the greater, the greater the total diameter of voluntary muscles;
muscle composition, i.e. the ratio of fast and slow muscle fibers c. contracting muscles.
TO coordination (central-nervous) factors include a set of central-nervous coordination mechanisms for controlling the muscular apparatus - mechanisms of intramuscular coordination and mechanisms of intermuscular coordination.
M Mechanisms of intramuscular coordination determine the number and frequency of impulses of motoneurons of a given muscle and the relationship of their impulses in time. Through these mechanisms, the central nervous system regulates the MPS of a given muscle, i.e., determines how close the force of an voluntary contraction of a given muscle is to its MS. The MPS indicator of any muscle group, even one joint, depends on the strength of contraction of many muscles. The perfection of intermuscular coordination is manifested in an adequate choice of the “necessary” synergistic muscles, in limiting the “unnecessary” activity of the antagonist muscles of this and other joints, and in increasing the activity of the antagonist muscles that provide fixation of adjacent joints, etc.
T Thus, the control of muscles when it is required to manifest their MPS is a complex task for the central nervous system. From this it is clear why, under normal conditions, the MPS of muscles is less than their MS. The difference between a muscle's MS and its MPS is called a strength deficit.
WITH silt deficiency in humans is defined as follows. On a special dynamometer, the MPS of the selected muscle group is measured, then its MS. To measure MS, the nerve that innervates a given muscle group is irritated with electrical impulses. The strength of electrical stimulation is chosen such as to excite all motor nerve fibers (axons of motor neurons). In this case, the frequency of stimulation is used, sufficient for the occurrence of complete tetanus of muscle fibers (usually 50-100 pulses / s). Thus, all muscle fibers of a given muscle group contract, developing the maximum possible tension (MS) for them.
WITH the silt deficiency of a given muscle group is the smaller, the more perfect the central control of the muscular apparatus. The magnitude of the power deficit depends on three factors:
psychological, emotional, state (attitude) of the subject;
the required number of simultaneously activated muscle groups
the degree of perfection of their arbitrary control.
P first factor. It is known that under certain emotional states a person can manifest such strength that far exceeds his maximum capabilities under normal conditions. Such emotional (stressful) states include, in particular, the state of an athlete during a competition. Under experimental conditions, a significant increase in MPS indicators (i.e., a decrease in strength deficit) is found with strong motivation (interest) of the subject, in situations that cause his strong emotional reaction, for example, after an unexpected sharp sound (shot). The same is noted with hypnosis, taking certain medications. At the same time, the positive effect (increase in MPS, decrease in strength deficit) is more pronounced in untrained subjects and weaker (or completely absent) in well-trained athletes. This points to a high degree perfection of the central control of the muscular apparatus in athletes.
IN second factor. Under the same measurement conditions, the magnitude of the force deficit is the greater, the more number simultaneously contracting muscle groups. For example, when the MPS of muscles that only adduct the thumb is measured, the strength deficit in different subjects is 5-15% of the MS of these muscles. When determining the MPS of the muscles adducting the thumb and bending its terminal phalanx, the power deficit increases to 20%. With the maximum voluntary contraction of large muscle groups of the lower leg, the power deficit is 30% (Ya.M. Kots).
T third factor. Its role is proved by various experiments. It has been shown, for example, that isometric training carried out at a certain position of the limb leads to a significant increase in MPS, measured in the same position. If measurements are taken in other positions of the limb, then the increase in MPS is insignificant or absent altogether. If the increase in MPS depended only on the increase in the diameter of the trained muscles (peripheral factor), then it would be detected at. measurements in any position of the limb. Consequently, in this case, the increase in MPS depends on the more perfect than before training, the central control of the muscular apparatus in the trained position.
R The role of the coordinating factor is also revealed when studying the index of relative voluntary strength, which is determined by dividing the MPS index by the value of the muscle diameter (Since only the anatomical diameter of the muscle can be measured in a person, for most muscles, not absolute voluntary strength (the ratio of MPS to the physiological diameter) is determined, but relative (the ratio of the MPS to the anatomical diameter. In sports pedagogy, the concept of "relative strength" refers to the ratio of the MPS to the athlete's weight.). So, after a 100-day training with the use of isometric exercises, the MPS of the muscles of the trained arm increased by 92%, and their cross-sectional area by 23% (Fig. 28). Accordingly, the relative arbitrary force increased on average from 6.3 to 10 kg/cm2. Therefore, systematic training can improve voluntary muscle control. The MPS of the muscles of the untrained arm also slightly increased due to the latter factor, since the cross-sectional area of the muscles of this arm did not change. This shows that more perfect central control of the muscles can manifest itself in relation to symmetrical muscle groups (the phenomenon of "transfer" of the training effect).
How it is known that the most high-threshold ("less excitable") are the fast motor units of the muscle. Their contribution to the overall tension of the muscle is especially great, since each of them contains many muscle fibers. Fast muscle fibers are thicker, have more myofibrils, and therefore the force of their contraction is higher than that of slow motor units. This explains why MPS depends on muscle composition: the more fast muscle fibers they contain, the higher their MPS.
TO When an athlete is faced with the task of developing significant muscle strength during the performance of a competitive exercise, he must systematically apply in training exercises that require the manifestation of great muscle strength (at least 70% of his MPS). In this case, voluntary muscle control is improved, and in particular the mechanisms of intramuscular coordination, which ensure the inclusion of as many motor units of the main muscles as possible, including the most high-threshold, fast motor units.
Skeletal muscle fibers are divided into fast and slow. The speed of muscle contraction is different and depends on their function. For example, rapidly declining calf muscle, and the eye muscle contracts even faster.
Rice. Types of muscle fibers
IN fast muscle fibers the sarcoplasmic reticulum is more developed, which contributes to the rapid release of calcium ions. They are called white muscle fibers.
slow muscles are built from smaller fibers and are called red because of their reddish color due to their high content of myoglobin.
Rice. Fast and slow muscle fibers
Table. Characterization of the three types of skeletal muscle fibers
|
Index |
Slow oxidative fibers |
Fast oxidative fibers |
fast glycolytic fibers |
|
The main source of ATP formation |
Oxidative phosphorylation |
glycolysis |
|
|
Mitochondria |
|||
|
capillaries |
|||
|
High (red muscles) |
High (red muscles) |
Low (white muscles) |
|
|
Activity of glycolysis enzymes |
Intermediate |
||
|
intermediate |
|||
|
Fatigue rate |
slow |
Intermediate |
|
|
Myosin ATPase activity |
|||
|
Shortening speed |
slow |
||
|
Fiber diameter |
|||
|
motor unit size |
|||
|
Motor axon diameter |
muscle strength
The strength of a muscle is determined by the maximum amount of load that it can lift, or by the maximum strength (tension) that it can develop under isometric conditions.
single muscle fiber able to develop an effort of 100-200 mg. There are approximately 15-30 million fibers in the body. If they acted in parallel in one direction and at the same time, they could create a voltage of 20-30 tons.
Muscle strength depends on a number of morphofunctional, physiological and physical factors.
Calculation of muscle strength
muscle strength increases with an increase in the area of their geometric and physiological cross section. The physiological cross section of a muscle is the sum of the cross sections of all muscle fibers along a line drawn perpendicular to the course of the muscle fibers.
In a muscle with a parallel course of fibers (for example, sartorius) the areas of geometric and physiological cross sections are equal. In muscles with an oblique course of fibers (intercostal), the physiological cross-sectional area is greater than the geometric area, and this contributes to an increase in muscle strength. The physiological section and strength of muscles with a feathery arrangement of muscle fibers, which is observed in most muscles of the body, increase even more.
In order to be able to compare the strength of muscle fibers in muscles with different histological structures, the concept of absolute muscle strength is used.
Absolute muscle strength- the maximum force developed by the muscle, in terms of 1 cm 2 of the physiological cross section. The absolute strength of the biceps is 11.9 kg / cm 2, the triceps muscle of the shoulder - 16.8, the gastrocnemius 5.9, smooth muscles - 1 kg / cm 2.
where A ms is muscle strength (kg / cm 2); P is the maximum load that the muscle can lift (kg); S is the area of the physiological cross section of the muscle (cm2).
Strength and speed of contraction, muscle fatigue depend on the percentage various types motor units in this muscle. The ratio of different types of motor units in the same muscle varies from person to person.
There are the following types of motor units:
- slow tireless (have a red color), they develop a small force of contraction, but can be in a state of tonic tension for a long time without signs of fatigue;
- fast, easy to tire (have a white color), their fibers develop a great force of contraction;
- fast, relatively resistant to fatigue, developing a relatively large force of contraction.
In different people, the ratio of the number of slow and fast motor units in the same muscle is genetically determined and can vary significantly. The greater the percentage of slow fibers in human muscles, the more it is adapted to long-term, but low-power work. Individuals with a high proportion of fast strong motor units in their muscles are able to develop greater strength, but are prone to rapid fatigue. However, it must be borne in mind that fatigue also depends on many other factors.
Muscle strength increases with moderate stretch. One of the explanations for this property of the muscles is that with moderate stretching of the sarcomere (up to 2.2 microns), the likelihood of formation of more connections between actin and myosin.
Rice. Relationship between force of contraction and sarcomere length
Rice. Relationship between muscle strength and length
Muscle strength depends on the frequency of nerve impulses sent to the muscle, synchronizing the contraction of a large number of motor units, predominantly involving one or another type of motor unit in the contraction.
The strength of contractions increases:
- when more motor units are involved in the process of contraction;
- when synchronizing the contraction of motor units;
- when more white motor units are involved in the contraction process.
If it is necessary to develop a small effort, slow, tireless motor units are activated first, then fast, fatigue-resistant ones. If it is necessary to develop a force of more than 20-25% of the maximum, then fast, easily fatigued motor units are involved in the contraction.
At a voltage of up to 75% of the maximum possible, almost all motor units are activated and a further increase in strength occurs due to an increase in the frequency of impulses sent to muscle fibers.
With weak contractions, the frequency of sending nerve impulses along the axons of motor neurons is 5-10 imp/s, and with great strength contractions can reach up to 50 imp/s.
IN childhood the increase in strength is mainly due to an increase in the thickness of muscle fibers, which is associated with an increase in the number of myofibrils in them. The increase in the number of fibers is insignificant.
During muscle training in adults, an increase in their strength is associated with an increase in myofibrils, and an increase in their endurance is due to an increase in the number of mitochondria and ATP production due to aerobic processes.
There is a relationship between strength and speed of muscle contraction. The rate of muscle contraction is the greater, the greater its length (due to the summation of the contractile effects of sarcomeres). It decreases as the load increases. Heavy loads can only be lifted when moving slowly. The maximum contraction speed achieved during human muscle contraction is about 8 m/s.
muscle power is equal to the product of muscle strength and the speed of shortening. The maximum power is reached at average speed muscle shortening. For the arm muscles, the maximum power (200 W) is achieved at a contraction speed of 2.5 m/s.
The strength of contraction and muscle power decrease with the development of fatigue.
Hand strength measurement Rice. 4.1. Wrist dynamometer Progress The measurement of hand strength is carried out with a manual dynamometer as follows: - the subject takes a dynamometer in his hand (the arrow is first brought to the zero position); ...Means and methods muscle relaxation In sports
The concept of "relaxation". Relaxation (from lat. relaxatio - "stress reduction") - relaxation. Arbitrary relaxation of muscles (relaxation) is based on the ability of a person to mentally, using a figurative representation, disconnect muscles from impulses coming from motor centers ...(Physical Culture)
Hand strength measurement
Equipment: wrist dynamometer (Fig. 4.1), calculation tables. Rice. 4.1. Wrist dynamometer Progress Measurement of hand strength is carried out with a manual dynamometer as follows: - the subject takes a dynamometer in his hand (the arrow is first brought to the zero position); - the indicator is directed...(HUMAN HYGIENE AND ECOLOGY)
Types of force, measurement of force
Max Strength(MS) is defined in isometric terms at electrical stimulation muscles. MPS - maximum arbitrary force, manifested in isometric conditions with an arbitrary contraction of the muscle. Power deficit(SD) is an indicator of the degree of coordination abilities ...(Human Physiology. Sport)
Definition of strength endurance
To determine endurance, reduce the compression force of the hand dynamometer so that it is 1/3 of the maximum. Using a stopwatch, determine the time during which such an effort will be held. Compare the value obtained with the figure characteristic of an adult organism (Table 4.1). Table 4.1...(HUMAN HYGIENE AND ECOLOGY)
Power devices based on thyristors and power transistors
Controlled Rectifiers Power devices include electronic devices that convert energy into electrical circuits, the currents in which are measured in tens, hundreds and even thousands of amperes, and the voltage values in hundreds and thousands of volts. These devices are often...(Electronics)
Today we will tell you in detail about what the dynamometer measures, and what varieties of this device exist. But before answering these and other questions, it is necessary to understand what the term "dynamometry" means. As you know, this word was formed from two Greek words: metron, that is, measure, and dynamis, strength.
It should be noted that this unit of measurement is especially often used in anthropometry, anthropology, neuropathology, during professional selection, the study of military contingents, fatigue, and so on.
What does a dynamometer measure?
From the foregoing, we can safely conclude that a dynamometer is a special device with which absolutely anyone can easily and quickly measure their own muscle strength.
By the way, the readings of such a device vary significantly depending on the duration and difficulty of professional work. In the event that this method allows you to obtain certain results in their graphical form, then it is called dynamography.
Types of dynamometers
Currently, the presented device has many different models. The most common among them is a medical manual dynamometer, which is designed to measure the muscle strength of the hand. It is not for nothing that such a device is called medical, as it is often used in hospitals and clinics, to equip a medical room in sanatoriums, sports facilities and schools.
However, the answer to the question of what the dynamometer measures is not only the muscle strength of the hand. After all, there are such varieties of this device, which are often used for a similar measurement of the strength of the muscles of the legs and torso, characterizing the degree of physical development of a person.
Medical dynamometer: appearance and calculations
With the help of such a hand-held apparatus, a physician can easily and quickly determine the strength of the muscles of the patient's hand. During this procedure, two measurements are alternately taken on each arm, and then the best result is recorded. Externally, the device resembles. However, it looks a little different, with a sensor and a measuring board. In addition, the dynamometer is not intended for training cyclic work, but for the only compression with the maximum possible for. If such a procedure is carried out exclusively for medical purposes, then the hospital employee is required to record the results in a special control log.
To get more objective indicators, subtract muscle strength. After all, its growth during training is quite closely related to the growth muscle mass and body weight of the athlete. For example, in order for you to be able to independently determine the relative magnitude of the strength of your own hands, you need those readings that were obtained in kilograms from a hand-held medical dynamometer, multiplied by a hundred, and then divided by the person's body weight. So, for previously untrained men, this index will be 60-70, and for women - 45-50%.
Definition of backbone strength
Having calculated the power of the hands, you can check the results in such basic exercise, How deadlift. It is in this movement that all the power qualities of a person will be visible. This is due to the fact that with such an exercise, the athlete uses all the major muscles of the body.
To carry out such a measurement, it is necessary to use a special device that looks very similar to a conventional foot expander. It consists of a hand grip and a footrest. However, instead of springs, this device has a cable with a peculiar in the middle.
The subject's task is to pull the handles towards themselves with the maximum possible force. In order to determine the required values, it is necessary to calculate the relative value of the deadlift in the same way as in the case of a hand-held medical device. Its results can be interpreted as follows:
- less than 170% - low;
- from 170% to 200% - below average;
- from 200% to 230% - average;
- from 230% to 250% - above average;
- more than 260% - high.
If in the process of training an athlete's relative strength indicators significantly increase, this indicates a significant increase in muscle strength and, accordingly, a percentage increase in the content of the muscle mass itself.
Factors that, one way or another, affect strength indicators
In the process of assessing the strength of the muscles for self-control, do not forget that it directly depends on such individual factors as:
- The age of the person.
- Gender identity.
- Athlete's body weight.
- Types of training influences.
- The degree of fatigue, etc.
In addition, indicators of muscle strength can vary significantly throughout the day. For example, the smallest value is observed in the morning and evening, and the largest - in the midst of the day, that is, in the middle.
It is also worth noting that a significant decrease in an athlete or an ordinary person is often noted during:
- general malaise;
- any disease;
- violations of the regime of the day and nutrition;
- emotional disorders or in a negative mood, etc.
Among other things, the values on the dynamometer can be lowered in the elderly, as well as in those who are over 40-50 years old. A similar situation is often observed in men or women who rarely engage in physical culture, including regular gymnastics, walking, and so on.
Why do you need to know strength indicators?
Not everyone knows how and what a dynamometer measures. However, such a medical device helps quite well for those who regularly play sports. After all, systematic self-observation allows a person to be creative about his daily training and healthy lifestyle life in general. Knowing the indicators of his own muscle strength, the athlete is able to effectively and rationally use physical culture to strengthen immunity and maintain health, as well as to increase efficiency and even professional growth.
