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SCIENTIFIC BACKGROUND (Answers to your educated clients’ questions)

Life means changes: everything is in constant movement; also the processes in a human organism constantly oscillate. Each cell of the organism is a world of its own that gets its sense and its meaning in connection to others. It is a part of the whole in tissues and organs that give sense to its functioning.

The final goal of all regulation mechanisms in life is maintaining harmony based on the principle "cause – effect” and is led by a goal set beforehand (Lasan 2004). Skeletal muscles create changes with movement; this is the cause that breaks the balance and is a condition for development. The effect is a reaction of the organism.


The nervous system is an efficient regulation mechanism that transmits information to all body parts to which the projections of nerve cells (neurons) spread and that reacts extremely fast to various changes in the environment and the body. The basic constituent unit of the nerve tissue is a nerve cell or a neuron.

A neuron consists of a cell body and projections (one or more) called nerve fibres. These are divided into dendrites and neurites or axons.

A nerve cell picks up stimuli from other nerve cells or sensory cells and gets stimulated. The impulse then spreads from the dendrites through the cell body to the axon and through the axon to the end of the nerve cell. Neurons are interconnected in a way that axon terminals (synaptic bulbs) are connected to dendrites or bodies of other nerve cells or cells of other tissues that are under direct control of the nervous system (muscles, glands). The point of "junction” between two nerve cells is called a synapse.

The synapse between a nerve cell and a muscular cell is called a neuromuscular junction. Therefore, main characteristics of the nervous system are exciteability (capacity to react to stimuli), capacity of transmission (transmission of stimuli) and interconnection of nerve cells (synapses).

The nervous system is divided into the central nervous system and the peripheral nervous system. The central nervous system that is mutually connected to all body parts consists of the cerebrum (telencephalon), brain stem (mesencephalon (midbrain), pons and medulla) and the spinal cord. The connection goes through the peripheral nervous system consisting of 12 pairs of cranial nerves and 31 pairs of spinal nerves that transmit all information to the central nervous system and out of it.

The peripheral nervous system is divided to somatic nervous system and the autonomic nervous system. The latter regulates the functioning of glands and internal organs while the former regulates the activity of striated muscles and enables the body to respond to the impulses from the receptors.

The autonomic nervous system releases two types of neurotransmitters: adrenaline and acetylcholine that have an accelerating or a braking effect on the functioning of internal organs. The autonomic nervous system consists of the parasymphatetic and the symphatetic part. The latter prepares the body for activity, reduces blood flow into digestive organs and brakes their functioning thus increasing the quantity of blood available to muscles.

The function of the parasymphatetic system is to help the body save energy and is active after exertion and during sleep.

The peripheral nervous system is divided to somatic nervous system and the autonomic nervous system. The latter regulates the functioning of glands and internal organs while the former regulates the activity of striated muscles and enables the body to respond to the impulses from the receptors.

The autonomic nervous system releases two types of neurotransmitters: adrenaline and acetylcholine that have an accelerating or a braking effect on the functioning of internal organs. The autonomic nervous system consists of the parasymphatetic and the symphatetic part. The latter prepares the body for activity, reduces blood flow into digestive organs and brakes their functioning thus increasing the quantity of blood available to muscles. The function of the parasymphatetic system is to help the body save energy and is active after exertion and during sleep.

Movement is enabled by two types of nerve cells: sensory nerve cells– for conveyance of information from the muscles to the central nervous system and motor nerve cells – for conveyance of commands from the central nervous system causing the muscles to contract. The skeletal muscle thus accepts impulses conveyed by motor fibres as a response to stimuli from the environment and the muscle itself. Very sensitive muscle receptors are located between muscle fibres and in tendons. These are muscle spindles and tendon organs also called proprioceptors or kinaesthetic receptors. Impulses are transmitted through sensory fibres of nerve cells to nervous centres (brain, spinal cord) from where they come back to the muscle through motor fibres of nerve cells. These reflexes are the basis for quick balancing of the position of the body.

The movement of muscles is possible if the muscle is stimulated with an alpha-motoneuron. To balance movement, feedback informations from proprioceptors are also necessary. The function of an alphamotoneuron is to stimulate the muscle fibers so they contract. A neurite of one motoneuron can at the end divide on numerous branches, each affecting one muscle cell. One alpha-motoneuron can innervate from 10 to 1700 muscle fibres. An alpha-motoneuron and all muscle fibres it innervates are referred to as a motor unit.
characteristic of a living organism
The muscle spindle is a receptor in the muscle that perceives changes in the length of muscle cells. Information on the speed of change in muscle fibre length travel through axon terminals and cause a reflex contraction in response to stretching within the muscle (the stretch reflex). A Golgi tendon organ senses tension developing in the tendon while it is stretching. It is located in tendons and is sensitive to a tension increase in tendons. The tension can be a consequence of stretching a relaxed muscle or of an increase in the force of its contraction (the Golgi tendon organ is more sensitive to the latter). These receptors send information on the tension in the muscle through the sensory path and inhibit the alpha-motoneuron of the contracting muscle.


There are two most important systems for regulation of all processes in our body and maintaining a balance – homeostasis: the nervous system and the hormonal system. The latter is much slower in its reactions in comparison to transmission of signals in the nervous system; however it is always monitoring the internal environment of the body and has the ability to detect the slightest disturbance that could jeopardise the homeostasis in the body.

Muscle activity includes coordinated linking of most of physiological and biochemical systems in the body. Such linking into a whole is possible only if the tissues and the systems are tightly interconnected. The nervous system is responsible for the larger part of the communication within the body environment while the endocrine system (the system of glands with internal secretion) senses and regulates all physiological responses of the body to any stimulus that could break the stable condition of the body.

The hormonal and the nervous system cooperate very well; they control body movement and all physiological processes. They differ in speed of transmission of signals. The nervous system is fast and effective in a given moment while the hormonal system functions much slower but the hormones remain in the blood much longer.

The functioning of the hormonal system (glands: thyroid, parathyroid gland, adrenal glands, sex glands etc.) is controlled by the central nervous system that regulates the secretion of hormones into the blood and the secretion of the hyphophysis. At first there must be an external stimulus or an impulse from the environment that will cause certain changes in the nervous system. The nervous system stimulates the hyphophysis through hormones which increases its functioning or brakes its functioning through hormone statin. The hyphophysis at first affects target organs with tropin hormones. The hyphophysis releases a certain tropic hormone that binds itself to cells of endocrine glands from which different hormones affecting target organs are secreted.

The principal centre of our nervous system that among other regulates our hormonal system is a hypothalamus. One part of the hypothalamus is the hyphophysis which is divided into two parts: adenohyphophysis that secretes tropic hormones and neurohyphophysis.

Adenohyphophysis, regulated by the hypothalamus with secretion of "releasing” hormones, secretes the thyrotropic hormones that regulate the activity of the thyroid, adrenocorticotropic hormone affecting the adrenal cortex and the gonadotropic hormone that regulates the activity of sex glands. Adenohyphophysis also secretes the growth hormone which accelerates growth and development. It is the only hormone that regulates the concentration of blood sugar at night time, increases the synthesis of proteins, the decomposition of fat and brakes the oxidation of glucose in the cells.

Epiphysis is a gland that disappears in the period of puberty. At night it secretes melatonin that regulates all biological rhythms in the body (sleeping, waking state, body temperature, a sense of pain, functioning of the cardiovascular system, pressure, coagulation, metabolism, cell division, emotional states), stimulates the immune system and protects the cells from diseases and changes due to age. Melatonin also brakes the occurrence of secondary sexual characteristics.

Neurohyphophysis secretes oxcytocin which causes the contraction of the uterus and increases the activity of mammary glands and the adiuretic hormone which increases the absorption of water from the kidneys back to the blood (it prevents dehydration and keeps water in the body).

The thyroid secretes the hormone thyroxine which increases basal metabolism - that is the energy necessary for maintaining life functions while being still. Thyroxine thus increases the oxidation of glucose in cells, facilitates the transmission of glucose from the small intestine to the blood, accelerates the synthesis of proteins and increases the oxidation of fatty acids. The thyroid also secretes calcitonin that reduces the concentration of calcium in the blood; calcitonin influences bone-building.

The functions of the parathyroid gland are to regulate the concentartion of calcium in the blood and the secretion of parathormone which affects cells that decompose the fibrocartilage callus. Target organs of this hormone are the bones, intestine and the kidneys.

Thymus located in front of the upper part of the heart has a central role in the immune system. Organism growth, development of sex organs, some liver functions and to a large extent our emotional condition depend on the activity of the thymus. The pancreas located slightly under the stomach secretes two important hormones: insulin and glucagon.

- balancing of the glucose level in the blood; when the level of glucose increases (hyperglycaemia), for example after a meal, the pancreas sends a signal for releasing insulin into the blood,
- insulin provides for the transport of glucose from the blood to the cells, especially to muscle and connective tissue,
- the main function of insulin is to decrease the available quantity of glucose in the blood,
- secretion of glucagon when the quantity of glucose in the blood falls under the permitted level (hypoglycaemia).

The kidneys release erythropoetin, a hormone that increases the creation of red blood cells (erythrocytes). Erythrocytes provide for the transportation of oxygen in the blood and the removal of carbon dioxide. Because of that many athletes decide to train on a certain altitude since adaptation to altitude increases the secretion of erythropoietin. Consequently the number of erythrocytes in the blood increases ensuring increased transport of oxygen which also means bigger endurance of the body during exertion.

The adrenal gland is located on the top of each kidney and consists of two parts: the adrenal medulla and the adrenal cortex. The former secretes adrenaline and noradrenaline while the letter secretes corticosteroids (cortisol) that increase the concentration of glucose in the blood.

During physical exertion the activity of the symapthetic nervous system increases preparing the cardiovascular system for physical exertion and consequent processes of thermoregulation (sweating) and the mechanisms for maintaining the constancy of the volume and the electrolytic structure/composition of body fluids (adiuretic hormone, aldosterone). At the same time the symapthetic nervous system increases the activity of the adrenal medulla which secretes adrenaline and noradrenaline. The adrenal cortex secretes cortisol. Both "stress” hormones, cortisol and adrenaline, prepare the organism for a bigger energy output. The concentration of blood sugar increases while the production of insulin decreases.

Both hormones have an important role in preparing the organism for immediate action where there is a choice of battle or escape and assist the organism to quickly confront with the current situation. They increase: the heart rate and the power of the heart muscle contraction, the metabolic level, glycogenesis (the transformation of glycogen into glucose in the liver and the muscles), the releasing of glucose and fatty acids in the blood, blood pressure and respiratory power.

The releasing of both hormones, adrenaline and noradrenaline, depends on different factors such as the change of the body position, psychological factors (stress) and workout. Adrenaline is released at a highly intensive workout (60-70% VO2 max), while noradrenaline is released already at 50% VO2 max. After workout adrenaline immediately falls back to the previous (normal) level while noradrenaline remains circling in the blood for a while.

During physical exertion the quantity of used glucose in the muscle cells is regulated locally following the principle: the more active the muscle cell the more permeable its membrane to glucose. Lower concentration of insulin during physical exertion also has the following advantage: the muscles have more fatty acids at disposal as energy sources and thus the stock of glucose is protected.

During physical exertion also the concentration of testosterone (the main anabolic of proteins in muscle cells) is reduced. The consequence is an undisturbed affect of cortisol on the decomposition of muscle proteins in the most active cells providing for co-operation of amino acids in energy supply of the muscles. Therefore a long rest is required so that the hormonal balance (reduction of cortisol, increase of insulin and testosterone) is re-established.

The growth hormone increases the synthesis of proteins in cells if the insulin level is high (the regeneration phase after physical exertion) and accelerates the decomposition of fat if the insulin level is low (during physical exertion). During intensive exertion the concentration of insulin reduces, therefore the growth hormone affects mainly the decomposition of fat and cortisol of proteins in the most active muscles. At night the organism is regenerating. Disposable amino acids in muscles that have been the most active are used for the reshaping of the muscle structure.

Beside cortisol the adrenal cortex also secretes aldosterone that affects the concentration of minerals in the blood. It regulates the concentration of sodium in body fluids and increases the volume of water. The concentration of aldosterone in the blood is regulated by the rennin hormone secreted by the kidneys. The ovaries are a gland stimulated by the hyphophysis. From the growing ovarian follicles and the "yellow body”(corpus luteum) two hormones are secreted: estrogen and progesterone. Testosterone, the male sex hormone, secreted by the testicles causes the increase of the muscle mass (hypertrophy) and the accumulation of minerals in the bones. Other effects of testosterone are: hairiness, deep voice, increased secretion of sebum from sebaceous glands (acinar gland), loosing of hair (if women had testosterone their hair would become much thinner), spermatogenesis (production of sperm cells), increase of the concentration of cholesterol and TCh (total cholesterol); psychological effects of testosterone are: aggressiveness, irritability, increase of the libido – sexual desire, bigger in case of men than women, manly behavior etc.

Male and female sex glands, adrenal cortex and the placenta are the sex hormones that affect the development and maintenance of tissue structures directly or indirectly connected with reproduction. The secretion of sex hormones is regulated by two gonadotrope hormones of the frontal lobe of the hyphophisis. The level of gonadotrope hormones depends on the activity of the hypothalamus and the circulating sex hormones.


The heart is a muscular organ responsible for pumping blood so that it circulates through the whole body. It is approximately the size of a human fist and is located in the middle of the thorax usually slightly offset to the left side of the body. The heart is enclosed by a sac, known as the pericardium. It is divided in two halves by the partitition, each one of them having two parts. The upper two are the left and the right atrium while the lower two are called the left and the right ventricle.

The main function of the heart is to push the blood through the body. Blood circulation is constant action. From the left atrium the blood moves to the left ventricle, a strong muscle, which pumps it out to the aorta (the big artery). The aorta divides into arteries, than to arterioles and finally to the tiniest vessels (the capillaries). In such a way the blood supplies the cells of all body organs.

The blood returns from the body to the right atrium through veins. From there it moves to the right ventricle that pushes the blood through the pulmonary circulation through the pulmonary artery into the lungs. In the lungs the carbon dioxide that originated in chemical energy processes is dropped off and oxygen picked up. Then the blood moves to the left atrium and restarts its flow through the body.

On the walls of blood vessels fat cells can accumulate making the transport of blood from the tissues to the heart more difficult. If blood vessels are totally closed they disable blood circulation which results in a heart attack. Workout is definitely a means of reducing risk of cardiovascular diseases.

The amount of blood pumped by the heart in a minute is referred to as a MINUTE VOLUME OF THE HEART (MVH). It is expressed in litres or millilitres per minute and represents the product of a pulse volume (PV=the amount of blood pumped by the heart in one contraction) and the heart beat frequency (Fh): MVH=PV x Fh (l/min)

The minute volume of the heart is changed proportionally to the level of our activity. Average minute volume of the heart while being still is approximately 5 l/min. Walking raises the value of MVH to approximately 7,5 l/min. Persistent intensive workout in case of highly trained athletes can raise it to 25 to 35 l/min (Guyton 1974).

Heart beat frequency in case of physical exertion can amount to 200 beats per minute (b/min) while the pulse volume can amount to 120 or 140 milliliters (maximum 200 ml).

The amount of blood that can be pumped by the heart in a minute depends on two main factors:
- the efficiency of the heart muscle to pump all the blood that came into the heart during diastole into the aorta
- lightness with which the blood flows through the body and returns to the heart (the filling of the heart during diastola) (Wilmoth 1986).

Blood pressure depends on the force with which the heart pumps the blood through the body and the resistance of smaller blood vessels. It varies from individual to individual and is higher during activity than while being still. In spite of certain discrepancies, normal values of blood pressure are 120/80 (expressed in millimetres of mercury, mmHg). The first value represents the systolic blood pressure (in the moment the heart compresses and pumps the blood into the vessels) while the second value represents the diastolic blood pressure (when the heart decompresses).

Blood pressure gets higher with age. Increased blood pressure is when the values surpass 160/90. Regular aerobic workout lowers blood pressure while being still as during exertion.

The organism has its system of "priorities” for the amount of blood received by each part of the body. While being still the biggest organs in the body get the most blood while during workout blood is redistributed to bigger muscle groups of the legs and the arms.


Aerobic workout enhances the power of the heart and its capacity of blood pumping; it assures that with every heart beat the heart pumps as much blood as possible, increasing the ability of faster exchange of oxygen from the lungs to the blood and finally to all parts of the body. Regular and adequately planned workout improves the functioning of the heart and unburdens it. One of the most important changes is that the muscle fibres in the wall of the heart can enlarge extending the ventricles (especially the left one) which can now receive and pump out more blood in each contraction. At the same time blood vessels that supply the heart muscle extend thus giving it more blood which also means more oxygen.

Since a trained
heart has a bigger power of contraction it pumps out more blood than an untrained one and beats slower when a person is still. The heart can do more - it can send more blood to the vessels and is contracted less times while doing that. It has been calculated that the heart of a trained person does up to 50 % less work compared to the heart of the person that does not work out. Thus the heart has more time to relax and recuperate for the next contraction.

Heart beat frequency will decrease as soon as we start training. The slowing down will occur in a year or two depending on the intensity and the duration of workout. Exceptions excluded, the heart beat is a good indicator of the individual’s "condition”: The slower the heart beat the better the condition. It is also an objective indicator of health improvement. The heart of a trained person is more resistant and can endure bigger burdens then an untrained heart. This vital organ becomes capable of doing more with less work.

Why should we strengthen the heart?

Scientists have determined that people who do physical work have much less heart diseases than people who sit during work. Today there is a conviction among physicians that regular physical activity prevents cardiovascular diseases and extends the life spam. Of course movement alone does not have such power of prevention. Smoking, excessive body weight and various stresses can contribute to getting ill from such diseases. Even so, movement is one of the irreplaceable factors in preventive as in the rehabilitation of the heart.

A lot of movement is one of the main ways of preventing or reducing arteriosclerotic conditions and high blood pressure. Arteriosclerosis is a condition of accumulation of fat on the inner lining of blood vessels.

These linings contract the blood vessel impeding blood flow. At the same time accumulating of fat at the wall decreases the elasticity of the vessel. Thus it cannot flexibly extend when the blood flows in, the pressure on the walls increases and this is what is referred to as high blood pressure (hypertension; blood pressure higher than 160/95 mmHg).

High amounts of cholesterol in the blood increase the risk of arteriosclerosis and thereby of high blood pressure. Cholesterol comes to the blood with certain nutrition (for example eggs, dairy products) or is produced by the liver when we consume saturated fat (for example most of animal fat, unskimmed milk, butter etc.). Scientists have determined that people who exercise a lot have less cholesterol in their blood.

Aerobic workout where we reach at least the minimum of the safety area of the minute heart beat reduces the amount of cholesterol in the blood and prevents or brakes the occurrence of arteriosclerosis and high blood pressure.

There is another way of preventing the occurrence of arteriosclerosis with physical activity. Apart from the coagulation system (that provides for blood curdling for example in case of bleeding) there is also the fibrinolitic system in the blood that prevents blood coagulation. The fibrinolitic system melts the fibre protein called the fibrin that is the main element of all blood clots. An effective fibrinolitic system thus prevents the occurrence of blood clots (and melts already existing clots) that can cause a thrombosis, heart attack or a stroke. Scientists have determined that fibrinolitic activity of the plasma is enhanced after physical exertion.

In intensive workout the organism needs more oxygen which is why not only the frequency of inhales but also the depth of breathing automatically increases. That causes a substantial extension of the thorax which preserves its elasticity and flexibility. The bigger the flexibility of the thorax the bigger the quantity of air that can be inhaled and thereby the amount of oxygen gained.

For improving the ability of the cardiovascular system the body has to be subjected to stress with a workout of a certain intensity and duration. The biggest increase in aerobic capability is reached if we train at 70 - 85 % of our maximal heart beat frequency. The changes in aerobic capability can also be reached with workout at a lower intensity especially in case of beginners. Knowledge about monitoring heart beat frequency is important so that we can assure a safe and effective level of workout.
characteristic of living organisms


The respiratory system consists of airways and the alveolar system of the lungs with a large breathing surface. The airway begins in the nasal cavity and continues in the trachea divided into two bronchi. In the right and the left wing of the lungs the bronchi divide into smaller and smaller bronchioles ending in clusters of air sacs called pulmonary alveolus.

The tubes of the airway are covered by the columnar epithelium constantly pulsing/beating and cleaning the walls of the trachea and the bronchi. It leads the filth out through the pharynx. In the muscle layer of the bigger tubes there are cartilaginous rings which make the tubes opened providing for unimpeded air flow. In smaller tubes the wall consists only of a muscle layer and can therefore contract. There are millions of pulmonary alveoli densely spread with capillares. The surface of all pulmonary alveoli is very big and in a short time big quantities of air are exchanged between the blood in the capillares and the alveoli.

The main function of the respiratory system is the exchange of two gases: oxygen and carbon dioxide. The gases diffuse in both directions through the walls of the alveoli as a consequence of different partial pressures of oxygen or carbon dioxide in the alveoli and the blood.

Since the concentration of oxygen in inhaled air is higher than in the blood the oxygen will diffuse into the blood while the path of the carbon dioxide will be exactly the opposite. The ratio and the speed of gas exchange vary on different factors, for example the speed and depth of ventilation, the speed of blood circulation through the lungs, the concentration of functional red cells in the blood and on partial pressures of oxygen and carbon dioxide in the alveoli and the blood. During physical activity the exchange of both gases is bigger.

Oxygen is crucial for creating energy in the organism while carbon dioxide is a waste product of the metabolism. Aerobic workout improves the capacity of respiratory organs, the heart and the blood for the transport of oxygen to active muscles.

Maximal aerobic capacity (or aerobic power) is determined with a test of measuring maximal usage of oxygen during workout referred to as VO2MAX and is expressed in litres of used oxygen per minute. Workout or training increases the VO2MAX but only to a certain extent that is genetically determined and represents the aerobic capacity of an individual. Appropriate workout is a precondition that the VO2MAX increases to the limit value. The maximal value expressed in millilitres of oxygen per kilogram of body mass per minute (ml/kg.min) is a measure for the aerobic capacity of an individual (maximal usage of oxygen).

While being still approximately 3.5 millilitres of oxygen per kilogram of body weight in one minute (3,5 ml/kg/min) is being used. The biggest officially measured VO2MAX in the case of a highly trained crosscountry skier was 92 ml/kg/min (McCoy 1990, from Powers & McLaren 1990). The table below shows maximal usage of oxygen in case of people of different sexes, ages and levels of training.

The maximal usage of oxygen occurs at a certain intensity of workout but it can be maintained for a relatively short time, approximately from 2 to 10 minutes, depending on the level of training. An ANAEROBIC THRESHOLD is a transition from anaerobic to aerobic condition. It is reached at a lower intensity of workout as necessary for the VO2MAX. Research shows that the anaerobic threshold is a prediction of an individual’s endurance and a measure of sub maximal cardio respiratory (cardio-vascular and respiratory) and metabolic reaction to workout.

The anaerobic threshold appears at workout intensity from 50 to 60 % VO2MAX; depends on the level of endurance of an individual that can be maintained for 30 minutes or a few hours again depending on the physical preparedness of an individual. For these reasons the anaerobic threshold is considered as a better predictor of endurance than the maximal usage of oxygen.

The anaerobic threshold is also very important for planning the appropriate workout intensity. This is the intensity where lactates start accumulating in the blood. The lactates are a side product of the anaerobic metabolism and accumulate in the blood because the body cannot secrete them from active muscles as quickly as they are produced. If the workout is continued in the intensity above the anaerobic threshold the person working out stops because of tiredness. If workout continues in the intensity just below the anaerobic threshold this does not happen.


The amount of energy entering into the organism from the environment is determined with the amount of disposable oxygen that is transported to the muscle cells in a certain time period. There it enters into chemical reactions with organic substances the product of which is carbon dioxide, water and energy, necessary for muscle activity (Bravničar 1991). Energy is released when high energy bonds in molecules of adenosine triphosphate (ATP) that is located in small proportions in cells, split. Millions of ATP molecules are stored in the muscles. When a muscle cell contracts, ATP molecules fall apart producing ADP (adenosine diphosphate) and released energy.


For a muscle to keep contracting, ADP must be converted back to ATP. There are many different ways of rebuilding ATP. In such regard two types of energy are relevant for this discussion: mechanical and chemical. Chemical energy in the body is a result of nutrition; some parts of food transform into energy components that decompose and are available to skeletal muscles for mechanical work.

Each body movement requires energy. The method by which the organism generates energy (reproduces ATP because it has been used in the muscles) is determined with intensity and duration of an activity. Activities that require a sudden burst of effort such as jumping, sprint racing and throwing need a big production of energy in a short time. Another extreme, activities such as long distance running, cycling etc. require a constant flow of smaller portions of energy during a longer period.

The first types of movement (sudden contractions) are supplied through energy systems that do not require oxygen. These are anaerobic chemical processes which literary means "without oxygen”. In such cases energy comes from high energy phosphate substances in the muscle (the phosphate energy system) or from the use of glycogen in the muscle resulting in the production of lactic acid (lactic energy system).

Longer activities such as running and cycling require a flow of oxygen for producing energy for constant muscle activation. Thus such activities are referred to as aerobic ("with oxygen”). The picture below shows a relation between various energy systems.

There are three ways of regenerating the ATP molecule:

(phosphate system) ensuring the fastest resynthesis of ATP with the help of creatine phosphate (CP):

Production takes place very fast therefore the muscles use this way of resynthesis of ATP in highly intensive exertions when the decomposition of ATP is high. Supplies of CP suffice only for a very intensive exertion that lasts for only a few seconds.

(lactic system) ensures a slower resynthesis of ATP with the help of glycolysis: Glycogen glucose pyruvic acid + energy for regenerating ATP As a side product lactic acid is created and is later on used in other processes of ATP regeneration.

This process is led without the presence of oxygen and assures energy for short term workout of high intensity. The main factor that prevents longer duration of such an intensive exertion is quick enhancement of the concentration of lactic acid in the muscles and the whole organism.


(the oxidative system) of ATP regeneration includes oxygen and assures enough energy for long term, medium term and less intensive exertions. It is a process of oxidation of carbon dioxides and fats; it depends of the quantity of fuel used in energy processes as of the supply of oxygen in cells, determined with the highest speed of oxygen transport.

ATP can be obtained from food of: carbohydrates, fats and proteins. As it was demonstrated the process of that can be whether aerobic or anaerobic.

The fastest source of energy are carbohydrates that are mono-, di- and polysaccharides. The simplest form of carbohydrates are sugars. Monosaccharides are glucose, fructose and galactose. Disaccharides are saccharose, lactose and maltose. Sugars are often marked as „bad", however they are an important part of our nutrition. Refined sugars that have all nutrition value removed (the so called „empty calories" without minerals, vitamins etc. that are vitally important for the body) are marked as harmful. Polysaccharides and complex carbohydrates are starch. They are composed of many units of monosaccharides and are found mostly in cereals, grain, vegetables and legumes. All people that work out should include a lot of starch enriched with sugar in their diet.

Carbohydrates are stored in muscle and liver cells in the form of glycogen. Muscle glycogen provides energy only for muscle fibres where it is stored while the liver glycogen maintains the concentration of glucose that is transported to active muscles in the blood.

The glucose in the blood (blood sugar) is a basic usable form of carbohydrates in the body. The level of blood sugar is important for normal functioning of the body for it is the only fuel used by the brain. If blood sugar level is low (hypoglycaemia) a stiffness appears because the whole system slows down. As already evident from the name, blood glucose is transported through the body in blood and in such a way it reaches active muscles. If the reserves of body glycogen are full, glucose enters fat cells and is thus stored as fat.

Fats represent 85% of the whole energy supply in the body stored in the form of triglycerides. Triglycerides are glycerol and free fat acid stored in fat cells and in skeletal muscles. Mobilization of free fat acids from fat reserves of muscles is important in maintaining body mass for during long term workout of moderate intensity free fat acids present a main source of fuel for ATP production. Free fat acids can be mobilized as an energy fuel only at the presence of oxygen (aerobic oxidative system).

In practice that means that stored fats can be used in the fastest way as a fuel or at low intensity activities (long slow walking, jogging etc.) or after the reserves of glycogen have already depleted. Therefore it is important for effective reduction of body mass that in early stages of the workout programme we use easy jogging, rhythmical exercises and not exercises of high intensity.

Proteins present a muscle fuel during physical exertion mainly as regards to muscle tissue decomposition. The table below demonstrates the percentage and the ratio between available amounts of various fuels, the speed of energy production and the time of stock depletion.


Anatomy is a science on human body structure. Basic terminology in anatomy is Greek or Latin while English terms are used only in cases where they are generally accepted. Otherwise Latin expressions are transformed into English.

The skeleton of an adult has a bit more then 200 bones.
For easier understanding we shall limit the discussion only to a narrow overview of the skeletal system, divided into:

- skeleton of the head and the trunk also called axial skeleton (includes the skull, spine, ribs and breastbone)
- appendicular skeleton (includes the shoulder girdle, pelvic girdle, upper limb and lower limb)

The skeleton of the trunk consists of:

- the spine-columna vertebralis (33 - 34 vertebrae: 7 cervical - v. cervicales, 12 thoracic - v. thoracicae, 5 lumbar - v. lumbales, 5 sacral - v. sacrales, 4-5 coccygeal - v. coccygeae)
- the thorax (ribs - costae, breastbone - sternum)

The skeleton of the upper limb consists of:
- arm bone - humerus
- forearm bones - radius (radial bone) and ulna
- metacarpal bones - ossa metacarpi
- bones of the fingers and toes - ossa digitorum

The skeleton of the lower limb consists of:

- bones of the pelvic girdle, pelvis (two hip bones - os coxae, consisting of three parts: iliac bone - os ilii, ischial bone - os ishii and pubic bone - os pubis, and the sacral bone)
- thigh bone - femur
- kneecap - patella
- leg bones - tibia (shin bone) and fibula
- tarsal bone - ossa tarsi

A JOINT is the location at which two or more bones make contact. Joints are divided into:
- joints of the axial skeleton (spine) The movements permitted in this joint are flexion, extension, side flexion, rotation.

- joints of the shoulder girdle
(sternoclavicular joint, acromioclavicular joint, glenohumeral joint, commonly known as the shoulder joint )

The movements permitted in this joint are flexion, extension, internal and external rotation, abduction, horizontal adduction, horizontal abduction, lift.

- elbow joint (combined joint)
The movements permitted in this joint are flexion, extension, internal and external rotation

- wrist joint
The movements permitted in this joint are flexion, extension, abduction, adduction, and circumduction.

- hip joint
The movements permitted in this joint are flexion, extension, internal and external rotation, abduction, adduction.

- knee
The movements permitted in this joint are flexion, extension, slight internal and external rotation but only when the knee is bent.

- ankle joint (upper, lower; combined)

The movements permitted in this joint are flexion, extension, internal and external rotation, inversion, eversion.


The shoulder girdle consists of the clavicle (collarbone) and the scapula (shoulder blade) that connect to a joint. The shoulder girdle is attached to the skeleton of the trunk only through the clavicular joint which importantly contributes to mobility in many directions. The arm is attached to the shoulder girdle so that it is slightly moved away from the trunk thus having more freedom in movement. The socket of the scapula meets the head of the humerus in a spheroidal joint (ball and socket joint). The shoulder joint is thus the most flexible joint in the body.

The knee joint is not only the biggest but also the most complexly structured joint in the human body in terms of diversity of its components. It is a hinge joint which is totally firm if extended while when flexed only slight medial and lateral rotation is possible. Differently shaped joint surfaces are levelled with two ‘semi-lunar’ cartilages (referring to their half-moon "C” shape) – lateral and medial meniscus. Their primary task is to function as a spring to intercept blows and pressures in walking, running and jumping.

The meniscus can be easily injured in aggressive rotating moves of the thigh and the shin bone when the knee is bended and also during joint wear. The patella (kneecap) mainly assists in increasing the leverage of the tendon of the anterior thigh muscle (m.quadriceps femoris), the strongest muscle in the body which is among other also the extensor of the knee joint.

The elbow-joint is a combined joint. In the same capsule there is the joint of the humerus and the ulna and that of the radius and the ulna. Movements possible in the elbow are flexion, extension and pronation or supination (turning the forearm over).

The skeleton of the arm consists of 27 bones connected with 36 joints. On the arm there is the wrist that has seven small short bones, the palm consisting of five short tubular bones and the fingers; the thumb has two while the other fingers have three joints. The bones of the wrist are turned to the arm and connect in an ellipsoid head of the joint. The palm is directly connected to the radius. This is why the otherwise stronger radius is injured more often than the ulna.

The pelvic girdle consists of two hip bones composed of three parts. The two bones meet on each side of the sacrum. With internal connection a flexible girdle called the pelvis is formed. The function of the pelvis is to carry the weight of the spine over to the legs. The pelvis of a woman is slightly larger than that of a man. The union of the three parts (illium, ischium and pubis) takes place in a large cup-shaped articular cavity, the acetabulum.

The hip joint is a spheroidal joint. The bottom of the cup-like acetabulum is filled by tender connective tissue and fat tissue. This tissue functions as a buffer and carries the vibration from the head of the thigh bone to the acetabulum of the hip. The flexibility of the hip joint is diminished on account of firmness and balance. The centre of gravity of the body is perpendicular to the horizontal rotation axis passing the hip joints approximately in the height of the third sacral vertebra. The pelvis turns around the axis as a pointer on a weighing machine. Almost all changes in the position of lower limbs are supplemented by simultaneous movement of the pelvis and the spine.

The skeleton of the leg consists of the instep, the foot and digit joints. There are two talar joints - the upper joint between the tibia and the talus bone (tibio-talar joint) and the lower one between the talus bone and the calcaneous bone (subtalar joint). With the tibio-talar joint the back of the foot is lifted up and down, while with the subtalar joint it is bended in and out. The talus bone transfers the weight to the arch of the foot( a flexible construction of the ankle and the bones of the midfoot). The muscles of the sole of the foot additionally strengthen this arch.


The muscle is a tissue that contracts and relaxes. In the human body there are approximately 600 striated muscles (skeletal muscles) moving the skeleton; the muscles also provide support to the body (dorsal muscles) and support to internal organs (abdominal muscles). Skeletal muscles present 40 to 50% of the whole body mass.

Muscles are composed of bundles of muscle cells (myofibres). The whole muscle and each of its units are enclosed in a sheath of connective tissue that is joint into tendons. Muscle cells are composed of numerous myofibrils that are composed of myofilaments. These contain two basic protein fibres: myosin and actin.

The movement of myofilaments that slide one over another, causes muscle contraction. Skeletal muscles are attached to bones, cartilage or ligaments (firm fibres connecting the bones) by tendons. Such connection of bones to the muscles provides for muscle contraction affecting the bones and transforming into movement.

Skeletal muscles usually work in pairs: when one muscle contracts the other relaxes (agonistic and antagonistic muscles). Muscles having mutually helpful functions or actions are referred to as synergistic muscles.

Muscle contraction is the sliding of thin actin filaments among thicker myosin filaments. Their length remains unchanged. During contraction (sliding) a connection between myosin and actin is established. Sliding myofilaments (myosin and actin) are additionally regulated by the proteins of tropomyosin and troponin. There must also be calcium and of course nervous stimulation. A command from the central nervous system is transported through the peripheral nervous fibre as a nervous impulse (electric voltage) to its motoric unit (contact between the nerve and the muscle cell) where it is transferred to the muscle cell through the nerve junction between the nervous fibre and the muscle cell with the help of special carriers (acetylcholine).

This causes the change of the cell membrane potential. Inside the cell, calcium is released from the stock. At the presence of tropin it causes the creation of cross-bridges between actin and myosin that are constantly formed in sliding of actin and myosin fibres; simultaneously a muscle fibre contracts. At the end of nervous firing and when the calcium stock is used the process runs in the opposite direction – crossbridges disappear. The muscle fibre slides into resting position.

Information about tension and position of muscles and joints constantly flow through sensory pathways from proprioceptors (in muscles and tendons). The aim of the proprioceptive system is that we are aware of limb position and movement – kinaesthetic awareness.

Skeletal muscles fibres react to stimuli that come from the alpha-motoneuron following the principle "all or nothing”. If the principle is achieved, they contract; otherwise they don’t react at all. Muscle force is modified by changing the number of muscle fibres that simultaneously contract and by changing the frequency of stimuli that are transported trough alpha-motoneurons to the motoric end plate. Skeletal muscles are never completely relaxed. They are always under some tension – this is called normal muscular tension or muscle tone, which is the sign of muscular readiness for action.

Major muscles are:

1. Dorsal muscles
- m. trapezius
- m. latissimus dorsi
- m. rhomboideus
- m. errector spinae (m. iliocostalis -thoracis, -lumborum, -cervicis; m. longis, simus -dorsi, -thoracis,
-cervicis, -capitis; m. spinalis dorsi, m. splenius -cervicis, -capitis; m.semi spinalis -cervicis, -capitis)
- intrinsic muscles of the back (m. multifidus, m. rotatores, m. semispinalis, m. intertransverus)

2. Abdominal muscles

- m. rectus abdominis
- m. obliquus externus abdominis
- m. obliquus internus abdominis
- m. transversus abdominis

3. Muscles of the thorax
- m. pectoralis major
- m. pectoralis minor

4. Upper limb muscles
- m. deltoideus
- m. biceps brachii
- m. brachialis
- m. triceps brachii
- m. brachioradialis

5. Lower limb muscles

Hip muscles:
- m. iliopsoas
- m. gluteus maximus, m. gluteus medius, m. gluteus minimus, m. piriformis,
- m. obturator internus, m. quadratus femoris

Thigh muscles:
- m. sartorius
- m. quadriceps femoris
- m. rectus femoris
- m. vastus lateralis
- m. vastus medialis
- m. vastus intermedius
- m. biceps femoris
- m. semimembranosus
- m. semitendinosus

- m. adductor (magnus, minimus, longus, brevis),
- m. gracilis,
- m. pectineus
- m. tensor fasciae latae

Leg muscles:
- m. tibialis anterior
- m. gastrocnemius
- m. soleus