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The method for determining muscle strength is called. Dynamometry

Female fitness
30.11.2019

Skeletal muscle fibers are classified as fast and slow. The speed of muscle contraction is different and depends on their function. For example, rapidly declining calf muscle, and eye muscle shrinks even faster.

Figure: Types 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 coloration due to their high myoglobin content.

Figure: 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)

Glycolysis enzyme activity

Intermediate

Intermediate

Fatigue rate

Slow

Intermediate

Myosin ATPase Activity

Shortening speed

Slow

Fiber diameter

Motor unit size

Motor axon diameter

Muscle strength

Muscle strength is determined by the maximum amount of weight that it can lift, or by the maximum force (tension) that it can develop under isometric conditions.

Single muscle fiber is 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 morphological, functional, physiological and physical factors.

Muscle strength calculation

Muscle strength increases with an increase in the area of \u200b\u200btheir 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 muscle with parallel course fibers (for example, sartorius muscle), the areas of the geometric and physiological cross-sections are equal. In muscles with an oblique course of fibers (intercostal), the physiological section area is larger than the geometric area and this contributes to an increase in muscle strength. The physiological section and strength increase even more in muscles with a feathery arrangement of muscle fibers, which is observed in most muscles of the body.

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 brachii muscle is 16.8, the gastrocnemius 5.9, the smooth muscle is 1 kg / cm 2.

where A ms - muscle strength (kg / cm 2); P is the maximum load that the muscle can lift (kg); S is the physiological cross-sectional area of \u200b\u200bthe muscle (cm 2).

Strength and speed of contraction, muscle fatigue depends on the percentage different types motor units included in this muscle. The ratio of different types of motor units in the same muscle is not the same for different people.

The following types of motor units are distinguished:

  • slow, tireless (red), 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, easily fatigued (white), their fibers develop 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 determined genetically and can vary significantly. The greater the percentage of slow fibers in a person's muscles, the more it is adapted to long-term, but low-power work. Individuals with a high content of fast strong motor units in their muscles are capable of developing great strength, but are prone to rapid fatigue. However, it should be borne in mind that fatigue also depends on many other factors.

Muscle strength increases at its moderate stretch. One of the explanations for this property of muscles is that with a moderate stretching of the sarcomere (up to 2.2 μm), the likelihood of the formation of more bonds between actin and myosin increases.

Figure: The relationship between the force of contraction and the length of the sarcomere

Figure: The relationship between muscle strength and length

Muscle strength depends on the frequency of nerve impulsessent to the muscle, synchronization of the contraction of a large number of motor units, predominant involvement in the contraction of one type or another of motor units.

The strength of the contractions increases:

  • when more motor units are involved in the reduction process;
  • 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, first the slow, indefatigable motor units are activated, then the fast, resistant to fatigue. If it is necessary to develop more than 20-25% of the maximum strength, then fast, easily fatigued motor units are involved in the contraction.

With 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 motoneurons is 5-10 pulses / s, and with a high force of contraction it can reach up to 50 pulses / 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.

When training muscles 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 the production of ATP due to aerobic processes.

There is a relationship between the strength and speed of muscle contraction. The greater its length, the greater the rate of muscle contraction (due to the summation of the contractile effects of sarcomeres). It decreases with increasing load. A heavy load can only be lifted when driving slowly. Maximum speed contraction achieved by contraction of human muscles is about 8 m / s.

Muscle power equal to the product muscle strength at the shortening speed. Maximum power is achieved at average speed shortening of muscles. For the arm muscles, the maximum power (200 W) is achieved at a contraction speed of 2.5 m / s.

Muscle contraction and power decrease as fatigue develops.

Factors affecting the magnitude of muscle strength:

1) muscle length:long muscles contract to a large
size than short ones (muscle shortening occurs by 1/3, sometimes by

2) number of muscle fibers(the more fibers
is part of the muscle, the greater its strength);

3) muscle fiber thickness(thick fibers develop
more stress than thin ones);

4) the direction of the fibers that make up the muscle(with oblique fibers
muscle strength is greater because they have more physiological transverse
section, high lifting force);

    original muscle length(the muscle works more efficiently after its moderate stretching);

    muscle attachment area(the larger the attachment area, the more strength the muscle can develop);

54 1) shoulder strength(the greater the shoulder of the muscle pull, the

more muscle strength);

8) innervation(the larger the number of motoneurons,

innervating this muscle, excited, the more motor

units are activated, the greater the voltage value or

muscle contractions; with an increase in the frequency of nerve impulses coming to

muscle, its contractile force increases).

Distinguish absoluteand relative muscle strength.

Relative muscle strength is the ratio of its maximum strength to the anatomical diameter (the cross-sectional area of \u200b\u200bthe muscle, held perpendicular to its length).

Absolute muscle strength - this is the ratio of its maximum strength to its physiological diameter (the sum of the cross-sectional areas of all muscle fibers that form the muscle). Picture 1.

Figure: 1. Diagram of the anatomical (solid line) and physiological (discontinuous

line) of muscle diameters of various shapes: / - ribbon-like muscle, // - spindle-shaped muscle, /// - single-pinnate muscle

To characterize the contractile ability of great importance

has a definition of absolute muscle strength. It must be borne in mind

that the physiological diameter (i.e. the cross-sectional area of \u200b\u200ball

muscle fibers in general) often notcoincides with the anatomical

diameter (i.e., the cross-sectional area of \u200b\u200bthe muscle). it

Static

is a job in which

muscle fibers

develop tension

but practically not

are shortened; movement

the body or its parts are not

going on.

1) holding

work when performing this

work visible

no action is observed,

but the muscle is contracted;

happens

balancing

resistance actions,

thrust moments

55
only parallel-fiber and

fusiform muscles, built from long muscle fibers. Have

cirrus muscles, according to the type of which most skeletal

human muscles, physiological diameter is slightly larger

anatomical. Thanks to this, the cirrus muscles are more

stronger than parallel-fibrous or fusiform.

The absolute strength of human muscles is expressed on average by the following

quantities (in kilograms per 1 cm 2): gastrocnemius + soleus -

6.24; extensors of the neck - 9.0; chewing - 10.0; biceps shoulder - 11.4;

shoulder - 12.1; three-headed shoulder - 16.8.

Between the strength and speed of muscle contraction, there is

specific ratio: the higher the strength developed by the muscle, the

less speed of its contraction,and vice versa, with increasing speed

reduction, the magnitude of the effort decreases (the ratio of force - speed, according to A.

2. The concept of muscles - antagonists and muscles-synergists.Types of muscle work

The performance of any motor act is the result of the friendly action of a number of individual muscles, since not one, but several muscles act on any joint. Functionally, depending on the direction of efforts developed by certain muscles, they are usually divided into synergists and antagonists.

Under synergiststhey understand such muscles that form friendly working complexes that make it possible to perform a certain movement. For example, the abdominal muscles, working in a friendly manner, tilt the trunk.

Individual muscles or muscle groups participating in various oppositely directed movements are called antagonists. For example, the muscle group that flexes the foot is

56 antagonist in relation to the group that unbends it, i.e.

muscles located on the back and front surfaces of the lower leg, -

antagonists.

This division is arbitrary, since under certain conditions, antagonist muscles can work as synergists. Thus, the flexor muscles and the extensor muscles of the trunk, working together, tilt the trunk to the side, i.e. work as synergists. The coordinated work of antagonist muscles and synergistic muscles ensures smooth movements and prevents injury.

In sports practice, muscles perform various types of work. In some cases, work leads to movement, in others - to maintaining a posture, fixing a position.

Types of muscle work

Dynamic

this is a work in which muscle fibers

shorten or lengthen, and occurs

movement of weight and movement of bones in the joints.

^ overcomingjob

muscle of any

resistance or force

the severity of this link

body when the moment of force

traction muscles (groups

muscles) more moment

gravity.



57

For example:a weight was put on the palm, which is held on an outstretched arm - this is a holding job. If the palm with the load rises up, then this is overcoming work; if the palm goes down under the influence of gravity, it is yielding work.

3. Muscle work on the principle of leverage

Muscles contract, set in motion the bones and act as levers.

A lever is any solid body fixed at one point around which movement occurs.

Mandatory elements of the lever are:

    fulcrum;

    point of application of force;

    lever arm -this is the distance from the fulcrum to the point of application of the force;

    shoulder strengthis the shortest distance from the fulcrum to the line of action of the force (Fig. 2).

Fig. 2. Lever diagram. Leverage shoulders (OA and OB), shoulders of forces (OA1 and OB1).

If the force of gravity acts at a right angle, then the arm of the force and the arm of the lever are the same in magnitude.

If we are talking about the human motor apparatus, then such a solid body is bone. The fulcrum around which the movements take place is the joint. The movement itself occurs due to the traction force of the muscles.

Bone levers - x these are the links of the body, movably connected at the joints under the action of the applied forces. They serve to transmit movement and work over a distance.

There are two types of levers: the first and second kind. If two forces (gravity and muscle pulling force) are applied on opposite sides of the pivot point of the lever and act in the same direction, then the body is a lever of the first kind. This lever is two-armed, because the shoulder of gravity and the traction of the muscles are located on either side of the fulcrum, respectively forming two equal shoulders. Such a lever is a lever of balance.

An example of a type 1 leveris the connection of the spine with the skull, i.e. atlantooccipital joint. It is also called the joint of balance, since the gravity of the skull is balanced by the traction force of the muscles of the back of the head (Fig. 3).

Dynamometry is a technique for measuring the strength of an individual muscle or muscle group using special devices - dynamometers.

Hand dynamometry

Hand dynamometry is a measurement of the strength of the flexor muscles of the fingers. Dynamometry of the hand looks like a one-step maximum impact on the device of muscle fibers. With the forearm extended, the subject squeezes the hand dynamometer with one hand. The study is carried out for both limbs, after which the data obtained are compared. With the help of a reversing device, a study is also carried out for the extensors of the forearm, flexors of the hip and lower leg.

Standard dynamometry and dynamography

Back dynamometry is a measurement of the strength of muscle groups that straighten the trunk. The bottom bar of the bench dynamometer should be fixed under the subject's feet. The subject grasps the upper bar with his hands and pulls it up. At the same time, he tries to straighten with the lower limbs extended at the knees.

In addition to back, reversible and hand-held spring dynamometers, there are mercury devices in which muscle force is determined as the level of pressure on the sensor using a mercury pressure gauge.

Dynamography is a type of study that allows you to register muscle contractions in the form of a series of curves on a graph. This method shows the long-term muscular effort of a muscle or muscle group in dynamics. Dynamography is used in balneology, neurology.


Dynamometry indicators are expressed in absolute values \u200b\u200bor relative (in relation to something, to mass, for example). These measurements are taken into account by anthropometry, physiology, sports hygiene and sports medicine. Also, the results obtained are used to assess the degree of physical development of a person.

Assessment of results

Various scales for assessing dynamometry indicators have been developed. There are averaged values \u200b\u200bof dynamometry results, which are taken as the norm. They differ depending on the height, gender and age category of the subject. However, other individual characteristics of the patient should also be considered.


One of the main indicators of physical development in children, from the age of eight to eighteen, is the back strength and the strength of the right hand, expressed in kilograms. In neurology, measurements of other muscle groups can also be used, if necessary. Most often, studies are performed for neurological diseases accompanied by muscle weakness (myasthenia gravis, paresis after stroke, assessment of the effectiveness of treatment of multiple sclerosis with weakness of the limbs, etc.).

Dynamometry in children of different sex and age gives different results, despite the same methodology. The measurement is carried out twice, after a short pause for rest.

Age indicators and dynamometry norm

So, the norms of indicators of the strength of the right hand in boys:
- from 8 to 11 years old vary from 13.0 to 18.5 kg;
- from 12 to 15 years old - from 21.6 to 37.6 kg;
- from 16 to 19 years old - from 45.9 to 51.0 kg.

For girls, these norms are much less important:
- from 8 to 11 years, respectively, the norm is from 9.8 to 17.1 kg;
- from 12 to 15 years, the norm is from 19.9 to 28.3;
- from 16 to 19 years old - from 31.3 to 33.8 kg.

Today we will tell you in detail what the dynamometer measures and what types 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: metron, that is, measure, and dynamis - force.

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, etc.

What does a dynamometer measure?

From all of the above, we can safely conclude that a dynamometer is special device, with the help of 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.

Dynamometer types

Currently, the presented device has many different models. The most common among them is a medical hand-held dynamometer, which is designed to measure the muscle strength of the hand. Such a device is not called medical for nothing, since it is often used in hospitals and clinics, to equip a medical office in sanatoriums, sports facilities and schools.

However, the answer to the question of what the dynamometer measures can be found not only in the muscular strength of the hand. After all, there are varieties of this device, which are often used for a similar measurement of the strength of the muscles of the legs and trunk, which characterize the degree of physical development of a particular person.

Medical dynamometer: appearance and calculations

With this hand-held device, the physician can easily and quickly determine the strength of the patient's hand muscles. During this procedure, two measurements are taken alternately on each hand, and then the best result is recorded. The externally presented device resembles, however, it looks a little different, with a sensor and a measuring board. In addition, the dynamometer is not intended for cyclic training 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 must enter the results obtained in a special control log.

To obtain more objective indicators, muscle strength should be subtracted. After all, its growth during training is quite closely interconnected with the growth of muscle mass and body weight of an athlete. For example, in order for you to be able to independently determine the relative strength of your own hands, you need those readings that were obtained in kilograms from a handheld medical dynamometer, multiplied by a hundred, and then divided by the weight of the human body. So, for previously untrained men, this index will be 60-70, and for women - 45-50%.

Definition of dead strength

By calculating the power of the hands, you can check the results in such basic exercise, as deadlift... It is in this movement that all the power qualities of a person will be visible. This is due to the fact that during this exercise the athlete uses all the main muscles of the body.

To carry out such a measurement, it is necessary to use a special device, which looks very similar to a conventional leg expander. It consists of a hand grip and a footrest. However, instead of springs, this device has a cable with a peculiar one in the middle.

The subject's task is to pull the handles towards himself with the greatest possible force. In order to determine the required values, the relative value of the deadlift should be calculated 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% - medium;
  • from 230% to 250% - above average;
  • more than 260% - high.

If in the process of training the athlete's relative strength indicators significantly increase, then this indicates a significant increase in muscle strength and, accordingly, a percentage increase in the content of the muscle mass itself.

Factors that, in 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:

  1. The age of the person.
  2. Gender.
  3. Athlete's body weight.
  4. Types of training influences.
  5. The degree of fatigue, etc.

In addition, muscle strength indicators can change significantly throughout the day. For example, the smallest value is observed in the morning and evening time, and the largest - in the very height 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 diseases;
  • violations of the daily routine and nutrition;
  • emotional disorders or with a negative mood, etc.

Among other things, the values \u200b\u200bon the dynamometer can be lowered in the elderly, as well as in those over 40-50 years old. A similar situation is often observed in men or women who are rarely involved in physical culture, including regular gymnastics, walking, etc.

Why do you need to know power indicators?

Not everyone knows how and what a dynamometer measures. However, such a medical device is pretty good at helping those who regularly play sports. After all, systematic self-observation allows a person to be creative in their daily workouts and healthy way life in general. Knowing the indicators of his own muscle strength, an athlete is able to effectively and efficiently use physical education to strengthen the immune system and maintain health, as well as to improve performance and even professional growth.

December 10

Zozhnik translated, revised and edited Greg Nukols' epic groundbreaking article on how muscle volume and strength are related. The article explains in detail, for example, why the average powerlifter is 61% stronger than the average bodybuilder for the same muscle volume.

Surely you have seen this picture in the gym: a huge muscular guy does squats with a 200 kg barbell, puffing and doing a few reps. Then a guy with much less massive legs works with the same barbell, but easily does more reps.

A similar pattern can be repeated in the bench press or deadlift. And from the course of school biology we were taught: the strength of a muscle depends on cross-sectional area (roughly speaking - from the thickness), however, science shows that this is a strong simplification and this is not quite the case.

Cross-sectional area of \u200b\u200bthe muscle.

As an example, look at how a 85-kg guy presses 205 kg from his chest:

However, much more massive guys cannot come close to such indicators in the bench.

The answer is simple: strength is influenced by many other factors besides muscle volume.

The average man weighs about 80 kg. If a person is not trained, then about 40% of his body weight is skeletal muscle or about 32 kg. Despite the fact that the growth of muscle mass is very strongly dependent on genetics, on average, a man is able to increase his muscle mass by 50% over 10 years of training, that is, add 16 more to his 32 kg of muscles.

Most likely, 7-8 kg of muscle from this increase will be added in the first year of hard training, another 2-3 kg - over the next couple of years, and the remaining 5-6 kg - over 7-8 years of hard training. This is a typical pattern for muscle growth. With an increase in muscle mass by about 50%, muscle strength will increase 2-4 times.

Roughly speaking, if on the first day of training a person can lift a weight of 10-15 kg to biceps, then later this result can grow to 20-30 kg.

With a squat: If you squatted with a 50-pound barbell in your first workouts, this weight can grow to 200 kg. This is not scientific data, just as an example - how strength indicators can grow. When lifting for biceps, strength can grow by about 2 times, and weight in squats - 4 times. But at the same time, muscle volume increased by only 50%. I.e it turns out that in comparison with the increase in mass, the force grows 4-8 times more.

Certainly muscle mass important for strength, but perhaps not determinative. Let's go over the main factors affecting strength and mass.

Muscle fibers

Studies show that the larger the muscle fiber, the greater its strength.

This graph shows a clear relationship between the size of muscle fibers and their strength:

How strength (vertical scale) depends on the size of muscle fibers (horizontal scale). Research: From Gilliver, 2009.

However, if absolute strength tends to grow with a larger volume of muscle fibers, relative strength (strength in relation to size), on the contrary, falls.

Let's see why this is happening.

There is an indicator for determining the strength of muscle fibers relative to their volume - “specific tension” (we will translate it as “specific force”). To do this, divide the maximum force by the cross-sectional area:

Muscle fibers: bodybuilders' specific fiber strength is 62% lower than lifters

So the point is that specific force is highly dependent on the type of muscle fibers.

In this study, researchers found that the specific muscle fiber strength of professional bodybuilders is as much as 62% lower than that of professional lifters.

That is, relatively speaking, the muscles of the average powerlifter are 62% stronger than the muscles of the average bodybuilder with the same volume.

What's more, bodybuilders' muscle fibers are also 41% weaker than untrained people based on their cross-sectional area. That is, per square centimeter of thickness, the muscles of bodybuilders are weaker than those of those who did not exercise at all (but in general, bodybuilders are, of course, stronger due to the total muscle volume).

This study compared different muscle fibers and found that the strongest muscle fibers are 3 times stronger than the weakest of the same thickness - a very big difference.

Muscle fibers grow faster in cross-sectional area than in strength

So both of these studies have shown that with an increase in the size of muscle fibers, their strength to thickness decreases... I.e they grow more in size than in strength.

The dependence is as follows: when the cross-sectional area of \u200b\u200bthe muscle is doubled, its strength grows only by 41%, and not 2 times.

In this plan correlates better with muscle fiber strength diameter fibers, not cross-sectional area (make this fix to school biology textbooks!)

Ultimately, scientists have reduced all indicators to this graph:

Horizontal: increase in the cross-sectional area of \u200b\u200bthe muscle. The blue line is the increase in diameter, the red line is the overall increase in force, the yellow line is the increase in specific force (by how much the force increases with an increase in the cross-sectional area).

The conclusion to be drawn is that as muscle volume increases, so does strength, but increases in muscle size (i.e., cross-sectional area) outpace gains in strength. These are averages collected from a variety of studies, and some studies vary.

For example, in this study, after 12 weeks of training, the experimental muscle section area increased by an average of 30%, but at the same time specific force has not changed (that is, we read between the lines, the strength has also increased by about 30%).

The results of this study are similar: the cross-sectional area of \u200b\u200bthe muscle increased by 28-45% in participants after 12 weeks of training, but the specific force did not change.

On the other hand, these 2 studies (one and two) showed an increase in muscle specific strength in the absence of muscle growth in volume. That is, the strength has increased, but the volume has not, and thanks to this combination, it turns out that the specific strength has increased.

In all of these 4 studies, strength increased compared to diameter muscles, but in comparison with cross-sectional area strength grew only if muscle fibers did not grow.

So, let's summarize an important topic with muscle fibers:

  • People differ greatly in the number of muscle fibers of one type or another.... Remember: specific force muscle fibers in lifters (training strength) are on average 61% more than in bodybuilders (training volume). Roughly speaking, with muscles of the same volume, lifters are stronger on average by 61%.
  • The weakest muscle fibers are 3 times weaker than the strongest... Their number in each person is determined genetically. This means that the hypothetically maximum possible difference in the strength of muscles of the same volume differs up to 3 times.
  • Specific strength (force per square centimeter of cross-sectional area) does not always increase with training... The point is that the cross-sectional area of \u200b\u200bmuscles grows faster on average than strength.

Muscle insertion site

An important factor in strength is how muscles are attached to bones and the length of the limbs.As you remember from the school physics course - the larger the lever, the easier it is to lift the weight.

If you apply force at point A, then it will take much more force to lift the same weight compared to point B.

Accordingly, the further the muscle is attached (and the shorter the limb), the greater the lever and the more weight can be raised. This partly explains why some pretty skinny guys are able to lift a lot more than some especially voluminous ones.

For example, this study states that the difference in strength depending on where muscles are attached in knee joint for different people is 16-25%. Here, how lucky with genetics.

Moreover, with the growth of muscles in volume moment of power increases: this happens because with the growth of the muscle in volume, the "angle of attack" changes slightly and this partly explains the fact that the force grows faster than the volume.

Andrew Vigotsky's research has some great pictures to illustrate how this happens:

The most important thing is the conclusion: the last picture demonstrating how, with increasing muscle thickness (cross-sectional area), the angle of application of forces changes, which means that it becomes easier for larger muscles to move the lever.

The ability of the nervous system to activate more fibers

Another factor in muscle strength, regardless of volume, is the ability of the central nervous system (CNS) to activate as many muscle fibers as possible to contract (and relax the antagonist fibers).

Roughly speaking, the ability to transmit the correct signal to muscle fibers as efficiently as possible - to strain some and relax other fibers. You have probably heard that in ordinary life we \u200b\u200bare able to transfer only a certain normal force to the muscles, but at a critical moment the force can grow many times over. In this place, examples are usually given of how a person lifts a car in order to save the life of a loved one (and there are indeed quite a few such examples).

However, scientific studies have not yet been able to fully prove this.

Scientists compared the strength of "voluntary" muscle contraction, and then with the help of electrical stimulation achieved even more - 100% tension of all muscle fibers.

As a result, it turned out that "Voluntary" reductions are about 90-95% of the maximum possible contractile force, which was achieved with the help of electrical stimulation ( it is not clear just what error and influence such "stimulating" conditions had on the antagonist muscles, which need to be relaxed to obtain more strength - approx. Zozhnika).

Scientists and the author of the text conclude that it is quite possible that some people will be able to significantly increase strength by training the transmission of brain signals to muscles, but most humans are not able to significantly increase strength just by improving their ability to activate more fibers.

Normalized Muscle Strength (NSM)

The maximum contractile force of a muscle depends on the volume of the muscle, the strength of the muscle fibers that make up it, on the "architecture" of the muscle, roughly speaking, on all the factors that we have indicated above.

According to research, muscle volume is responsible for about 50% of the difference in power indicators from different people.

Another 10-20% of the difference in strength is attributed to "architectural" factors such as insertion site, fascia length.

The rest of the factors responsible for the remaining 30-40% of the difference in strength do not depend on muscle size at all..

In order to consider these factors, it is important to introduce the concept - normalized muscle strength (NFM) is the strength of a muscle in comparison with its sectional area. Roughly speaking, how strong a muscle is compared to its size.

Most studies (but not all) show that HCM increases with exercise. But at the same time, as we discussed above (in the section on specific force), the increase in volume alone does not provide such an opportunity, this means that the growth of strength is provided not only by an increase in volume, an improvement in the passage of muscle signals, but by other factors (the same which is responsible for the remaining 30-40% of the difference in strength).

What are these factors?

Improving the quality of connective tissue

One of these factors is with an increase in fitness improves the quality of connective tissue, which transfers efforts from muscles to bones... With an increase in the quality of connective tissue, most of the efforts are transferred to the skeleton, which means that the strength grows with the same volume (that is, the normalized strength grows).

According to research, up to 80% of the strength of the muscle fiber is transferred to the surrounding tissues, which attach the muscle fibers to the fascia using a number of important proteins (endomysium, perimysium, epimysium, and others). This force is transferred to the tendons, increasing the overall transmitted force from the muscles to the skeleton.

This study, for example, shows that BEFORE NSM training (strength of entire muscle per cross-sectional area) was 23% higher than the specific strength of muscle fibers (the strength of the muscle fibers per cross-sectional area of \u200b\u200bthese fibers).

AND AFTER NSM training(specific force of the entire muscle) was 36% higher(specific strength of muscle fibers). It means that the strength of the entire muscle during training grows better than the strength of the sum of all muscle fibers.

Scientists attribute this to the growth of connective tissue, which allows more efficient transmission of force from fibers to bones.

Above and below, tendons are schematically shown - between them is a muscle fiber. With an increase in fitness (right figure), the connective tissue around the muscle fibers grows, the number and quality of joints grow, allowing more efficient transmission of the muscle fiber force to the tendons.

The idea that the quality of the force transmitting fibers improves with increasing fitness (and the picture above) comes from a 1989 study and is still mostly theory.

However, there is a 2010 study that supports this position. In the course of this study, with unchanged muscle fiber parameters (specific force, peak force) total strength of the entire muscle grew by 17% on average (but with a wide variation in different people: from 6% to 28%).

Anthropometry as a factor of strength

In addition to all of the above factors of muscle strength, the overall anthropometry of the body also affects the amount of force emitted and how efficiently this force can be transmitted when the joints are flexed (regardless of the moment of force of individual joints).

Take the barbell squat as an example. Hypothetical situation: 2 equally trained people with muscles of the same size and fiber composition, identically attached to the bones. If, however, person A has a hip 20% longer than person B, then person B should hypothetically squat with 20% more weight.

However, in reality, everything does not happen quite like that, due to the fact that when the length of the bones changes, the place of muscle attachment changes proportionally.

Thus, if person A's thigh is 20% longer, then the place of muscle attachment to the thigh bone (the amount of leverage) is also proportional - 20% further - which means that the length of the thigh is leveled by the gain in muscle attachment further from the joint. But this average... In reality, anthropometric data, of course, differ from person to person.

For example, it has been observed that powerlifters with longer shins and shorter thighs tend to squat with more weight than those with longer thighs relative to the shin. A similar observation is made about the length of the shoulder and the barbell press from the chest.

Regardless of all other factors, the anthropometry of the body makes adjustments to strength, however, measuring this factor is difficult, since it is difficult to separate it from others.

Training specificity

You are well aware of the specificity of training: what you train improves. Science says specificity works for a wide variety of aspects of training. Much of this effect works because the nervous system learns to make certain movements more efficiently.

Here's a simple example. This study is often used as an example to illustrate the principle of specificity:

  • Group 1 trained with a weight of 30% of 1RM - 3 reps each until muscle failure.
  • Group 2 trained at 80% of 1RM - and did only 1 repetition until muscle failure.
  • Group 3 trained with a weight of 80% of 1RM - 3 reps each to muscle failure.

The greatest improvement in strength was expected to be achieved in Group 3 - heavy weight training and 3 sets of exercise.

However, when at the end of the study, among all groups, the maximum number of repetitions with a weight of 30% of 1RM was checked, then the group that trained with 30% of 1RM showed the best result. Consequently, when testing the maximum weight at 1RM, the results improved better for those who trained at 80% of the 1RM.

Another interesting detail in this study: when they began to check how the results in static strength changed (it was not trained in any of the 3 groups), the results in the growth of this indicator were the same, since all 3 groups did not specifically train this strength indicator.

With the growth of experience and the refinement of technique, an increase in strength is associated. Moreover, in complex multi-joint exercises, where large muscle groups the effect of training is greater than in small muscles.

This graph shows how as the number of repetitions increases (horizontal scale), the proportion of errors in the exercise decreases.