What is the predominant fuel used by muscle cells during extended low or moderate intensity activity quizlet?

Many physiological and nutritional demands occur within the body during exercise. As muscles contract, the demand for oxygen, hydrogen and other key nutrients increases. The human body requires a continuous supply of energy to perform its many functions. As energy demands increase with exercise, additional energy must be supplied or the exercise will end.

Factors of performance

Whether a recreational athlete or an elite athlete, many factors influence performance including, but not limited to, diet, hydration, fitness level, intensity and duration. There are many factors that predict what source of fuel will be used. Proteins, fats and carbohydrates are all possible sources of fuel for exercise and muscle contraction.

During moderate-intensity exercise, roughly half of the energy is derived from glycogen, while the other half comes from glucose in the blood and fatty acids. Carbohydrates (glucose/glycogen) serve as the primary source of fuel as duration and intensity increase. If exercise continues for a significant period of time, fatty acids will serve as the fuel source when glycogen stores are nearly depleted. It must be noted that fat metabolism cannot occur without the presence of glucose, and thus muscle glycogen and blood glucose are the limiting factors in performance. Protein or, more specifically, amino acids, will only be used as an energy source if other calories are insufficient.

Food choices

A person’s diet will influence which source of fuel is used and therefore, performance level. If a person consumes a high-carbohydrate diet, more glycogen will be used for fuel. If the diet is high in fat, fat will be used as the fuel source. A high-fat diet is not recommended as even the leanest person has plenty of stored fat for long endurance exercise. A high-fat, low-carbohydrate diet can lead to poor performance due to low glycogen stores. As a guideline for endurance athletes, roughly 60–70 percent of calories should come from carbohydrates, 10–15 percent protein and 20–30 percent from fat. You should consume a well-balanced diet containing carbohydrates, protein and fat during training periods.

Carbohydrate intake before, during and after exercise is crucial. A high-carbohydrate pre-exercise meal not only prevents hunger pangs during exercise, it also provides optimal blood glucose levels for endurance exercising and increases glycogen stores. Avoid high-fat foods in a pre-exercise meal as it delays stomach emptying and takes longer to digest. This meal should be three to four hours before an event.

Marathon runners talk about “hitting a brick wall.” This refers to the time when fuel sources have been drained and not replaced. When glycogen and blood glucose levels are low, the body is out of fuel and cannot keep going no matter how fast an athlete wants to go.

For exercise lasting longer than an hour, you should ingest carbohydrates to fuel the brain and muscles. You can maintain a sufficient supply of energy by consuming 26–30 grams of carbohydrates every 30 minutes during exercise. Most sports drinks provide 15–20 grams of carbohydrate, so consuming 8–12 ounces every 15–30 minutes is recommended. As for protein, only a few amino acids can actually be used directly as energy. Thus, protein consumption during exercise is not advantageous.

Fluid intake

Muscle glycogen stores must be replaced after endurance exercise. Resynthesis of muscle glycogen is promoted when carbohydrates are consumed immediately after exercise. Unfortunately, due to an elevated body temperature, appetite is usually depressed and many athletes have difficulty consuming foods immediately after exercise. Drinking carbohydrates via a sports drink or shake provides carbohydrates and promotes rehydration.

Adequate fluid intake is also crucial for any athlete. You should weigh yourself before and after an endurance event, especially during hot weather. For each pound lost during exercise, drink three cups of fluid. Fluids should not be restricted before, during or after an event. Athletes should not rely on thirst as a sign of fluid loss. Consume roughly 14–22 ounces of fluid before an event, 6–12 ounces every 15–30 minutes during an event, and after the event, 16–24 ounces for every pound of body weight lost.

Metabolism is a sum of events which are carried out in the human body to create energy and other substances necessary for its activities. In our organism there are catabolic and anabolic processes.

Catabolism is a process during which organic matter is broken down and the energy is simultaneously released. It is characterized by missing reserves of glycogen and mobilisation of non-saccharide sources of energy – fats and proteins. Catabolism takes place during increased movement activity and is necessary to sustain life functions.

Anabolism, on the other hand, is a energy-consuming process during which substances are created. The substrate supply exceeds the immediate need. The organism creates energy reserves, tissues are created and renewed. Anabolic processes are prevalent in situations of reduced physical activity.

The basic nutrients (carbohydrates, lipids, proteins) are present in food we eat. Those are transformed and absorbed through the digestive system. Carbohydrates break down into individual carbohydrates (monosaccharides) where the glucose ranks among the most important ones. Lipids break down into free fatty acids and glycerol. Proteins break down into amino acids. These simple agents can then become involved in more complicated processes.

Carbohydrates are used in both anaerobic and aerobic activities. ATP resynthesizes from glycogen (muscle glycogen, liver glycogen) which transforms into glucose. Supplies of glycogen in the human body are restricted. Lipids are used in endurance-based movement activity of low intensity. While the use of proteins in the ATP resynthesis is very limited, free fatty acids are used to a large extent. Glucose is generated through gluconeogenesis.

Muscle metabolism

Muscles need energy to produce contractions (Fig. 6). The energy is derived from adenosine triphosphate (ATP) present in muscles. Muscles tend to contain only limited quantities of ATP. When depleted, ATP needs to be resynthesized from other sources, namely creatine phosphate (CP) and muscle glycogen. Other supplies of glycogen are stored in the liver and the human body is also able to resynthesize ATP from lipids, i.e. free fatty acids. Different modes of energy coverage are used depending on intensity and duration of the workload put on the organism.

Figure 6 Energy for muscles

The ATP-CP system

The above mentioned ATP and CP are the energy sources of muscle contraction (Fig. 7, 8, 9). The production of energy used in muscle contraction takes place through the anaerobic way (without oxygen).

Figure 7 ATP molecule

Figure 8 ATPase (ATP breakdown and energy production for muscle contraction)

Figure 9 ATP resynthesis from CP

Anaerobic glycolysis

It is a chemical process during which ATP gets renewed from glycogen, i.e. glucose in an anaerobic way (without access to oxygen). In these processes lactate, i.e. salt of the lactic acid is generated in muscles. This energy system produces 2 molecules of ATP. Glycolysis - transformation of glucose into 2 molecules of the pyruvate generating the net yield from ATP molecules and 2 NADH molecules (anaerobic breakdown of glucose into pyruvate and lactate) – see. Fig. 10.

Oxydative system

This is a chemical process during which the ATP resynthesis takes place through an aerobic way (with access to oxygen). Both glycogen or glucose and free fatty acids act here as sources of energy.

Aerobic glycolysis takes place in the cytoplasm of the cell where 34 ATP molecules are generated from the glycogen, i.e. glucose with oxygen present (Fig. 10).

Figure 10 Anaerobic and aerobic glycolysis

Free fatty acids present in mitochondria of muscle fibres transformed into acetyl CoA are used in the ATP resynthesis. Acetyl CoA enters the Krebs cycle and thus ATP molecules are generated.

Individual energy systems get involved according to the intensity of a movement activity carried out. If the performance is conducted at the maximum level, there is a gradual involvement of all the systems (Fig. 11, 12).

Figure 11 Energy coverage under maximum workload

Figure 12 Energy coverage under maximum workload

Types of muscle fibres

Human muscle fibres have distinct qualities. Although nowadays almost 30 types of muscle fibres are known to be present in the human body, we tend to work only with the following three types:

Slow red muscle fibre I (SO - slow oxidative fibres)

The slow red muscle fibre is typified by a high aerobic capacity and resistance to fatigue. As their anaerobic capacity is slow, they are not able to show great muscle strength. Muscle contraction tends to be slow – 110 ms/muscle contraction. One motoric unit contains about 10-180 muscle fibres.

Fast red muscle fibre IIa (FOG – fast oxidative glycolytic fibres)

The fast red muscle fibre shares some of qualities with a slow fibre or a fibre of IIx type. This fibre is typified by medium aerobic capacity and resistance to fatigue. It also shows high anaerobic capacity and is able to display great muscle strength. The speed of contraction is 50 ms/muscle contraction. One motoric unit contains about 300-800 fibres.

Fast white fibre IIx (FG – fast glycolytic fibre)

Unlike the previously mentioned types the fast white fibre is characterized by low aerobic capacity and tendency to fast fatigue. On the other hand, it has the greatest anaerobic capacity and is able to display considerable muscle strength. The speed of contraction is 50 ms/muscle contraction. One motor unit contains about 300-800 fibres.

The volume of this type muscle fibres is genetically given (up to 90 %) (Jančík et al., 2007) and varies in individual persons. In the average population the ratio of slow to fast fibres is 1:1. The following Figure (Fig. 13) shows the ratio of slow to fast fibres in athletes engaged in different disciplines.

Figure 13 Ratio of fast (type FG and FOG) to slow (type SO) fibres in different type athletes

In muscle contraction individual types of muscle fibres get activated in accordance with the intensity of muscle movement. During low intensity exercise slow fibres are primarily recruited. However, with increasing intensity of exercise fast fibres get activated. It is important to note here that the fibre ratio differs in different muscles of the human body. For example, postural muscles tend to contain more slow fibres.

Page 2

Muscle contraction is initiated by the nervous system which together with the endocrine system controls the human organism. They are responsible for the steadiness of the inner environment and coordination of all the bodily functions. The nerve cell, a neuron, is the basic unit of the nervous system (Fig. 14). Cells attending to muscles are called motoneurons. A neuron is composed of the body and projections. The shorter ones are called dendrites, the long one is axon. Through the dendrite the neuron is able to obtain information from other neurons. The axon then passes the processed information to other cells (e.g. muscle cells). The information is further spread along the neuron through changes in the voltage in the cell membrane, the so called action potential. The transfer of information between individual nerve cells is then secured by chemical agents. Once the action potential has reached the end of an axon, the mediator is released.

Figure 14 Organization of neuron

Neuromuscular junction is a place where the last motoneuron and the muscle cell meet. The binding of the mediator (acetylcholine) to the receptor brings about another action potential which spreads along the muscle cell membranes.

Central and peripheral nervous system

The nervous system is made up of the central and peripheral nervous systems (Fig. 15).

Figure 15 Organization of the nervous system

The central nervous system (CNS) is composed of the brain and the spinal cord.

The brain is made up of (Fig. 16):

• medulla oblongata
• pons Varolii
• midbrain or mesencephalon
• little brain or cerebellum
• interbrain or diencephalon: thalamus and hypothalamus
• basal ganglia
• limbic system
• cerebral cortex

Different parts of the CNS are interconnected through ascending and descending pathways creating functional wholes.

Figure 16 Structure of the brain

The peripheral nervous system is composed of 12 pairs of head nerves connected to the brain and of 31 pairs of spinal nerves attached to the spinal cord. Sensoric nerves transfer information from body receptors to the CNS. Motoric nerves transport information from the CNS to muscle fibres.

Autonomic nervous system

The autonomic nervous system controls the activities of the inner organs (heart, glands, smooth muscles). It is involuntary. It is made up of sympathetic and parasympathetic systems which both try to keep the functional balance of the human body with the possibility of either of the systems taking prevalence in certain situations. In athletes the sympathetic system becomes dominant during movement activities while the parasympathetic system prevails under resting conditions.

The sympathetic nervous system enhances organ activity (increase in HR, increase in BP, etc.) while the parasympathetic nervous system produces the opposite effect, i.e. reduces organ activity (decrease in HR).

Page 3

In addition to the nervous system, muscles, i.e. movement activity is controlled by the hormonal system. Hormones are produced in endocrine glands from which they are transported through blood to the target cells. The releasing of hormones from a number of target glands is affected by the adenohypophysis. Hormones produced by the neurohyphysis include e.g. antidiuretic hormone (ADH) which decreases the production of urine. Besides other functions growth hormone (GH) is responsible for growth of the muscle mass. The presence of glucose in the blood referred to as glycemia is maintained by insulin and glucagon. Insulin transports the glucose to cells (during a movement activity especially into muscle cells) and thus reduces the blood glucose level. Glucagon, however, has the opposite, effect; it increases the blood glucose level. These hormones are released from the pancreas. During exercise the insulin level decreases in proportion with the intensity of the aerobic work. During an anaerobic activity the insulin production tends to rise.

During exercise epinephrine (adrenaline) and norepinephrine (noradrenaline) are released from the adrenal medulla into the blood. They transport energy to muscles and enhance the activity of the heart and other organs promoting muscle contraction.

In connection to adaptation of an organism to training at higher altitudes we need to mention erythropoietin which controls red blood cell production.

Testosterone, the principal male sex hormone, has anabolic effects and enhances protein biosynthesis. Through protein stimulation it reinforces bone production and growth of muscle tissue.

The last two mentioned hormones are often abused as doping substances in sports.

Page 4

A human organism does not need energy only to produce movement activity. Energy is also released during the sleep. All events taking place in the human body require energy. When issuing nutritional recommendations it is necessary to be aware of how much energy the human body gives out under resting conditions as well as during various daily routines or sports activities.

A number of units are used to measure energy. Most frequently these are joules (J), or kJ. In Northern America calorie (cal), or kcal (kilocalories) are used. In measuring of the energy output the MET unit is used, or the so called metabolic equivalent where 1 MET = 3.5 VO2 ml/min/kg.

Basal metabolism refers to the minimum energy consumption necessary to sustain basic physiological functions (about 1.200-2.400 kcal/24hours which is roughly equivalent to 5.000-10.000 kJ/24 hours).

Resting metabolism refers to energy output under resting conditions (sleep, lying position, sitting position) which is about 10% higher than of the basal metabolism.

Activity metabolism refers to energy output in various activities, whether daily routine or sports ones (Tab. 1).

The minimum energy output during a routine daily activity is about 1.800-3.000 kcal/24hours which is roughly equivalent to 7.600-12.600 kJ/24 hours. This is, however, influenced by a number of factors including sex, age, body build and overall fitness of a person in question. We are more likely to detect the increased BM values in athletes than in the non-sporting population.

The minimum energy output during a daily routine activity is about 1.800-3.000 kcal/24 hours which is roughly equivalent to 7.600-12.600 kJ/24 hours.

Table 1 Energy expenditure values for the selected activities and sports activities

Energy expenditure measurement

The level of energy expenditure may be determined through direct and indirect calorimetry. Being technically and financially demanding the direct calorimetry is used very rarely. The person examined is left in a closed room from which the air is conducted away. The heat produced by the organism is measured. The indirect method is used more frequently.

The Herris-Benedict formula presents the simplest way to estimate the basal metabolism:

For females:

BMR (kcal) = 655 + (9.6 × weight in kg) + (1.8 × height in cm) - (4.7 × age in years)

For males:

BMR (kcal) = 66 + (13.7 × weight in kg) + (5 × height in cm) - (6.8 × age in years)

e.g. 50-year old woman, with the weight of 65 kg and height of 165 cm will calculate BMR using the formula in the following way:
BMR = 655 + (9.6 × 65) + (1.8 × 165) - (4.7 × 50) = 1 348 kcal = 5 640 kJ

Charts (Tab. 2, 3) are usually used to measure energy expenditure during 24 hours where individual activities are matched with the value of the basal metabolic rate (BMR) which expresses in percentage by how much an activity value is greater than the one of the basal metabolic rate (100%).

FORMULA

Table 2 Mean increase of energy expenditure in various habitual activities (adjusted according to Heller, 2005)

Table 3 Mean increase of energy expenditure in various physical and athletic activities (adjusted according to Heller, 2005)

The O2 measurement using an air analysator presents a more accurate method to measure energy expenditure. This method which recognizes individual differences may be used to measure both basal (resting) metabolism and energy expenditure in various movement activities. The value of the oxygen intake varies depending on the intensity of physical exercise.

Fatigue

Fatigue is a physiological state which follows after a period of physical as well as mental stress. In fact it is a defensive mechanism acting to protect our organism from a possible strain injury. Muscle fatigue results from the reduced production (resynthesis) of macroergic phosphates (ATP) accompanied by critical reduction of energy reserves or accumulated metabolites. Fatigue may be of total, local, physical, mental or acute or chronic kinds.

Viewed from the perspective of concrete metabolic changes in muscles the fast (anaerobic) fatigue and slow (aerobic) fatigue are recognized.

Acute fatigue refers to existing common fatigue felt as a direct consequence of an ongoing activity while chronic fatigue results from long-term strain where remnants of fatigue accumulate. Pathological fatigue beyond physiological dimension is often encountered too. Here we talk about the overtraining syndrome (OS).

The overtraining syndrome is characterized by reduced performance accompanied by disorders both in the area of regulation of physiological functions and the mental area.

Fully developed overtraining is not common and it needs to be differentiated from short-term overload or overreaching. Chronic condition of overtraining is characterized by excessively rising intensity of the training load, both repetitive and permanent, as well as by insufficient recovery.

The term overload refers to the planned, systematic and progressive increase of the load to achieve increase in the overall performance. Overreaching refers to repetitive acute overload without adequate recovery where the adaptive abilities of an individual are exceeded. This condition results in decreased performance spanning a few weeks or months. Both the overtraining syndrome and a subsequent recovery period usually take many more weeks or months.

Comment:
Máček, Radvanský (2011) add to the topic of over-training syndrome: "The term over-training has been abandoned in recent years because according to present opinions it does not represent the essence of the problem and has been replaced by term unexplained under-performance syndrome (UPS). The reason for this change is a distortion of causes of the pathological state using the original term, which states an inadequate increase in intensity or duration of training load as the only cause of this state, while there might be not only more causes, but also the mechanism is much more complicated."

Page 5

The cardiorespiratory system is in fact a transport system which enables the intake and transfer of oxygen and other substances into tissues and which eliminates the carbon dioxide and other dangerous substances from the organism. It is composed of the respiratory and circulatory system. The latter forms the subject matter of this chapter.

Organization of the circulatory system, the heart

The circulatory system is made up of the heart and vessels. The heart (Fg. 17) is the central organ which works as a pump transporting oxygen throughout the blood vessels.

Figure 17 Structure of the heart

The heart activity

Like the skeletal muscles the heart is controlled by electrical impulses generated by heart.

The conduction system of the heart is formed by the sinus (sinoatrial) node generating the fastest electrical impulses. Under normal circumstances the heart is controlled by the sinus node, a natural pacemaker which under resting conditions generates regular impulses within the range of 60-100*min-1. Electrical impulses then further spread into the atrioventricular node, bundle of Hiss, Tawara's nodes and Purkinje fibres (Fig. 18).

Figure 18 Conduction system of the heart

Physiological parameters of the circulatory system

Heart rate (HR) = a number of contractions per minute, given in beats per minute.

Stroke volume (Qs) = volume of blood pumped from the heart through one systole, given in ml.

Cardiac output (Q) = the volume of blood pumped from the heart during one minute, given in 1/min.

Blood pressure (BP) = is the pressure exerted by circulating blood upon the walls of blood vessels. During each heartbeat, BP varies between a maximum (systolic) and a minimum (diastolic) pressure; given in mmHg.

Reaction and adaptation of the circulatory system to workload

Heart rate

The value of resting heart rate tends to be about 70 beats/min in the average middle-aged population. HR decreases in proportion with rising age.

Response: Heart rate increases with workload (Fig. 19). Under constant workload HR rises dramatically and then it stabilizes. Under workload of increasing intensity, HR increases proportionally. If an individual carries out a movement activity of maximum intensity, the HRmax is reached. The HRmax value of a 20-year old man is about 200 beats per min. In the absence of workload, the HR returns to the original values.

Figure 19 Graph showing various HR values under workload

The HR values may be estimated based on the formula of 220-age.

Adaptation: The endurance trained individuals show the so called vagotonia – reduction in the resting HR values to the region under 50 beats/min. For example, elite long-distance runners, cyclists, cross country skiers, etc. show values of around 30 beats/min. This is given by the heart hypertrophy (explained later).

Heart rate may be detected using the following methods:

• palpation on the radial artery
• listening at the apex of the heart
• through electrical apparatuses

HR is best detected through palpations on the radial artery. We use 2-3 fingers to feel for the artery. As a thumb tends to contain a large artery itself, we do not use it to palpate the artery. Heart rate is measured for 20 seconds, the value obtained is multiplied by 3.

We assess the heart rate through listening most frequently at the apex of the heart using sthetoscope (normally at the doctor's).

The most frequently used apparatuses to measure HR are the so called sport-testers. There are many kinds of them, of which the latest ones include built-in GPS. In addition to measuring HR, they also measure the speed and distance of running, etc. A sport-tester consists of a chest belt with two electrodes which read the electrical activity of the heart in a similar way to ECG. The values measured show on a wrist watch. The values may be downloaded to a computer and thus it is possible to record and evaluate the training practice.

The HRV apparatus to assess the heart rate variability works similarly to a sport-tester. Like the latest sport-testers it records the value for each heart beat.

ECG reads the electrical activity of the heart using electrodes. The most frequently used one in the modern medicine is the 12-lead ECG where the curve consists of waves and swings of a typical shape and duration. Here we distinguish the P-wave (atrial depolarization), complex QRS (ventricular depolarization) and the T-wave (ventricular repolarization) – Fig. 20. The HR may easily be calculated; the interval between two adjacent R-swings equals the distance of two adjacent beats.

Figure 20 Generation of excitation and the ECG curve

Stroke volume

The resting values of the systolic volume in the average man are in the region of 70 ml.

Response: Under workload the values tend to rise, depending again on the workload intensity. The maximum values may be around 130 ml.

Adaptation: In endurance trained individuals the resting values are in the region of 100 ml. This increase results from excentric heart hypertrophy during which heart ventricles are enlarged and the heart is able to expel more blood at the same time. This makes it possible for the person to achieve higher values of up to 200 ml under workload.

Cardiac output

The resting values of the minute heart volume are about 5 litres in men and a little less in women.

Response: The values grow in proportion with the rising intensity of workload. Under maximum intensity the values exceeding 25l/min may be detected.

Adaptation: In endurance trained individuals the values increase up to the level of 35l/min. This again is given by the heart hypertrophy.

The following picture (Fig. 21) shows blood redistribution under resting conditions and high intensity workload.

Figure 21 Blood distribution in organs under resting conditions and during heavy exercise

Blood pressure

The ideal blood pressure values are in the region of 120/80 mmHg. Hypertension, i.e. increased blood pressure, occurs if the pressure exceeds the level of 140/90 mmHg while hypotension, decreased blood pressure is that of 100/65 mmHg and lower.

Response: The blood pressure value changes under workload depending on its type and intensity. Under dynamic workload conditions the systolic pressure increases. Maximum values may be detected under submaximal workload intensity where they could exceed the 200 mmHg level. The diastolic pressure, however, may decrease under submaximal intensity. The static workload normally results in the increase of both the systolic and diastolic pressure.

While in the past classic mercury based apparatuses were used, nowadays the blood pressure may be measured through automatic or semiautomatic tonometres which are attached to an arm, wrist or finger. To detect the value of pressure a sthetoscope is used.

Page 6

The respiratory system is the basic element of the transport system (Fig. 22).

Figure 22 Structure of the respiratory system

The structure of the respiratory system

The respiratory system is composed of the respiratory pathways or airways and the lungs which are its central organ. The air is inhaled into the system through the nose and the nasal cavity. It further progresses into the larynx and trachea (windpipe) later branching into two bronchi (sg. bronchus) that enter the lungs and split into bronchioles. Subsequently the air finally reaches the alveoli which are blood-perfused thin-walled air sacs. This is where the oxygen is transported into the blood.

Breathing may be divided into two main stages: inspiration and expiration. Breathing is a muscular activity. In inspiration breathing muscles are employed, on inspiration the diaphragm contracts and moves down and the intercostal muscles push the ribs up which lifts the rib cage and creates space for the enlarged lungs. Inspiration is facilitated through pressure changes inside the pleural cavity.

On expiration breathing muscles relax, ribs move down and the chest space decreases.

Physiological parameters of the breathing system

The breathing frequency (BF) = a number of inspirations per minute, given in breaths per minute.

Tidal volume (VT) = the volume of air exhaled in one expiration or inspiration, given in litres.

Ventilation (VE)= the volume of air inhaled (inhaled minute volume) or exhaled (exhaled minute volume) from a person's lungs, given in litres per minute.

Vital capacity (VC) = the maximum amount of air a person can expel from the lungs after a maximum inspiration, given in litres.

Oxygen uptake (VO2) = volume of oxygen received by an organism per minute, given in ml/min/kg. VO2 max = maximum oxygen uptake.

Carbon-dioxide production (VCO2) = volume of the exhaled CO2 per minute, given in ml/min/kg.

Respiratory exchange ratio (RER), respiratory quotient (RQ) = the ratio of the exhaled CO2 to the inhaled O2.

The ventilation equivalent for oxygen (VE, VO2) = volume of oxygen inhaled from one litre of the air.

Oxygen pulse (VO2/HR) = volume of oxygen transported into the blood circulation during one heart contraction.

Response and adaptation of the respiratory system to workload

Breathing frequency

The values of resting breathing frequency in the average population stand at about 16 breaths per minute.

Response: Under workload the BF values increase depending on the workload intensity. Maximum values are in the region of 40 breaths per minute.

Adaptation: The increased volume of the lungs, i.e. the increase in the breathing volume in the trained individuals results in the decrease in the BF resting values which may be under 10 breaths per minute. The maximum values can be as 60 breaths per minute high.

Tidal volume

The VT values in the average population are around 0.5 l.

Response: Under workload the VT values tend to rise up to the level of 2.5 litres.

Adaptation: In some endurance-trained individuals there occurs an increase in the resting VT values of up to 1 litre or more. Under workload the values may reach about 60% of VC, i.e. over 4 litres.

Ventilation

The minute ventilation may be calculated through multiplying the breathing frequency by the tidal volume (VE=BF*VT). Under resting conditions we get the values of around 10 l both in the sporting and non-sporting population.

Response: Under workload the ventilation rises, its maximum values may approach 120 l per min. If the ventilation reaches the level of over 40-50 l, a person will usually breathe with an open mouth.

Adaptation: Physical exercise may increase the ventilation up to the level of 180 l/min.

Vital capacity

The VC is a static parameter. The measured values are affected by a couple of factors: sex, age, body surface, fitness, etc. The average female population reaches the value of about 3-4 litres, in men it is 4-5.5 litres.

Response: The test is not conducted under workload. It is normally carried out after exercise. The low intensity workload may result in the increase of VC values. An individual needs to practise breathing.

Adaptation: Endurance training results in the increase of the VC capacity values which may even exceed the level of 6 litres. The highest values of up to 8 litres have been observed in swimmers. This is caused by exhalation into water which puts up more resistance than the air.

Oxygen uptake (VO2)

The oxygen volume values under resting conditions are about 3.5ml/min/kg.

Response: Rising intensity of workload is accompanied by the growing oxygen intake. The maximum values in women and men reach 35 ml/min/kg and 45 ml/min/kg respectively.

Adaptation: Adaptation to endurance training leads to the increase in maximum values. The values may reach the level of 90 ml/min/kg in world-class cross-country skiers. Endurance training results in the reduction of oxygen intake in various speed zones, the so called economy of running.

Oxygen pulse (VO2/HR)

The resting values are in the region of 5ml.

Response: The maximum values in non-trained individuals are 15-16 ml in men and 10-11 ml in women.

Adaptation: In endurance athletes the pulse oxygen reaches the value of 30-35 ml.

Page 7

Sports training affects the athlete's performance. From the physiological point of view we understand the training to be a process of adaptation to workload – adaptation of the athlete's organism to the increased body workload. It is both a structural and functional adaptation of the organ systems. Thanks to these adaptations movement abilities are developed.

Supercompensation

Supercompensation refers to the raised level of the energetic potential and the subsequent raised functional ability of the organism, both resulting from the previous workload – Fig. 23.

Figure 23 Supercompensation

Principles of the optimal training workload

Effective sports training must adhere to basic principles. Here we refer to the interconnectedness of elementary features of workload such as volume, intensity and recovery duration (Fig. 24).

Training volume – duration and frequency of training

Training intensity- effort made in a particular movement activity (intensity of workload on the muscles and transport system).

Recovery duration – time between training units

Highly intensive training with a smaller volume workload develops muscle speed and strength while lower intensity training of great volume workload develops aerobic capacity, i.e. endurance.

Figure 24 Optimal training model

Training cycle

Macrocycle = a yearly training cycle: preparation period, pre-competition period, competition, transition period – see Fig. 25.

Mesocycle = 1 month (4 weeks)

Microcycle = 1 week (7 days)

Figure 25 Contribution of individual training periods during the macrocycle

Adaptation of an organism to anaerobic (strength-speed) training

Adaptation of an organism to strength training:

During strength training the organism increases its anaerobic capacity, the myokinase activity is growing and there also occurs hypertrophy of fast muscle fibres.

Adaptation of an organism to speed training

Following the speed training there is an increase in the content and utilization of ATP and CP. Similarly to the after strength training situation there is hypertrophy of fast muscle fibres. Speed-endurance training raises the activity of the glycolytic system resulting in increased glycogen utilization.

Adaptation of an organism to anaerobic, i.e. endurance training

Training designed to develop endurance increases the amount of mitochondria in muscle and contributes to blood perfusion in muscle (muscle capillarization). It also enhances the anaerobic capacity, muscle glycogen values, lipase activity and the activity of the enzymes of the respiratory chain. There also occurs hypertrophy of slow muscle fibres which is not so significant as in fast muscle fibres.

Page 8

The environment tends to have a profound effect on sports performance. In the following charter we will look at how temperatures whether high or low tend to affect athletes' performance.

Thermoregulation

The body temperature is controlled by the brain. The hypothalamus works like a thermostat, it helps to keep and balance the natural body temperature. Under resting conditions the organism keeps a stable body temperature of 37°C.

If a person is exposed to higher temperatures in the immediate environment or is subjected to a movement activity which increases the body temperature, the body temperature rises. This upsets the homeostasis of the organism which sets off its defence mechanisms.

Response and adaptation of an organism to exercise in hot temperatures

The generation of heat occurs mainly in the nucleus, especially in the livers and muscles. Under workload up to 70% of heat is generated in muscles, the rest is produced in the other organs.

The following picture (Fig. 26) shows the major mechanisms of heat generation.

Figure 26 Mechanisms of heat generation

Mechanisms activated by heat according to Ganong (2005)

Increased heat generation:

• skin vasodilatation
• sweating (perspiration)
• more intensive breathing

Decreased heat generation:

• loss of appetite
• apathy and inactivity

Perspiration – evaporation (Rokyta, 2000, Hampl)

Perspiration presents the most effective mechanism of heat generation or output under physical workload. Through perspiration the body loses up to 80% of its heat while under resting conditions it is mere 10%. It is the only way of heat output in situations where the temperature of the environment is higher than the body temperature. Through perspiration sweat expelled through the skin surface gets evaporated thus taking away a certain amount of heat. Under physical workload this mechanism is launched by the adrenaline, while under resting conditions sweat glands are innervated by sympathetic cholinergic nerve fibres. The blood cools down in deep epidermis and progresses to deeper tissues. This manner of heat generation depends on the air humidity of the environment in question. The sweat evaporates faster when exposed to dry air than when exposed to humid air of the same temperature. In tropical forests of up to 90% humidity, sweat does not evaporate, it pours down the skin and the cooling is therefore not that effective. This is when the right choice of clothes becomes very important, it should never prevent sweat evaporation.

Sweat is produced by the sweat glands from plasma filtration. There are about 2.5 mil sweat glands in the human body, about 200 /1mm2 on a palm and 10-20/1mm2 on a trunk. Sweat is mostly formed by water, ions (Na+, K+ and Cl-), lactic acid and urea. In substantial perspiration the sweat tends to contain significantly more sodium and chlorides (in trained persons the losses of minerals tend to be smaller). Under heavy workload and in heat the body may lose up to 1 litre of sweat per hour per 1 m2 of the body surface. Unless liquid losses are not sufficiently compensated, dehydration may occur and basic life functions may be jeopardized.

Through evaporation the body loses water and ions (the daily loss of salt amounts to 15-30g). After a 1-6-week stay in a hot environment, sweat secretion increases to 2-3 litres per hour which may accelerate heat emission up to 10 times. Adaptation of the organism to heat results in increased water losses but this is compensated by decreased salt losses down to 3-5 g per day due to aldosterone effects.

Hyperthermia (organism overheating)

Organism overheating (Fig. 27) may result from physically demanding movement activity, hard work in hot weather, but also from being in crowded places such as at concerts etc. Overheating refers to the state of an organism where mechanisms in charge of thermoregulation stop working. The hypothalamus starts overheating and thus loses the ability to regulate the temperature. Hyperthermia symptoms include stoppage of perspiration, hot and dry skin, tachycardia and tachypnoea, confusion, faintness and unconsciousness. Overheating may affect persons of higher age or persons with cardiovascular diseases. Children and obese people may also run the risk of hyperthermia due to the hindered heat emission which results from higher insulation caused by the fatty layer in the latter.

Figure 27 Hyperthermia

Response of cardiovascular system to heat

Due to the transport of heat from muscles to surface body areas the cardiovascular system tends to become strained in heat. This situation leads to the increase of the minute cardiac output (Q), enhanced skin blood perfusion and deep epidermis blood perfusion which is compensated by the decrease in blood-perfusion to other areas (digestive and excretory system). The heart rate (HR) is growing in comparison with the workload in a cold environment.

Overheating prevention

Prevention of overheating includes lowering the intensity of workload and inclusion of frequent breaks in the shade. Persons in a hot environment are recommended to carry out physical exercise in the early morning or evening hours of the day. They are also advised to choose light and airy clothes capable of draining the sweat off the body surface.

Adaptation to heat

Repetitive workload in heat results in the enhanced ability of the organism to conduct heat away from the body and in the reduced risk of exhaustion and thermoregulation failure. Adaptation consists in the adjustment of perspiration and blood circulation. Acclimatized persons start sweating earlier and thus reduce their skin temperature. Significant temperature losses in heat enable the adapted people to transfer more blood to working muscles. Those adapted to heat show a lower body temperature and lower heart rate (HR) than those not acclimatized when under the same physical load.

Response and adaptation of an organism to workload in cold conditions

Cold stressors include cold water and cold air

Mechanisms activated by cold according to Ganong (2005):

Increase in the heat production through:

• muscle shivers
• hunger
• increased voluntary activity
• enhanced secretion of noradrenaline and adrenaline

Decrease in heat losses through:

• skin vasoconstriction
• lying curled up
• piloerection

Shiver

A shiver presents the most important defence mechanism against cold. It is caused by non-synchronized rhythmic muscle twitches which do not result in a changed position. This emerging muscle activity most probably derives from the reflex mechanism of the muscle spindle. Stress increases the generation of heat in an organism up to three times and simultaneously decreases skin blood-perfusion while raising blood-perfusion of muscles.

Non-shivering thermogenesis

Non-shivering thermogenesis derives from the effects of both adrenaline and noradrenaline from the sympathicus in brown fatty tissue (in newborn babies) and possibly also from white fatty tissues in skeletal muscles (in adults). The volume of heat thus produced is twice as big. Tyroxine contributes to heat generation by up to 50% in all the organs. This type of heat, however, gets activated only after a few weeks in a cold environment.

Hypothermia

Hypothermia (Fig. 28) occurs when core temperature drops below 35°C. In the first stage the body attempts to stop the temperature decrease by shivering, vasoconstriction and acceleration of the heart frequency. When the core temperature reaches the value of 30°C the person becomes unconscious. Temperature decline is accompanied by the decline in the basal metabolism which at the body temperature of 28°C drops to the half of its normal values. Managed hypothermia is used in heart and brain surgeries.

Figure 28 Hypothermia

Adaptation to cold

The International Commission for Thermal Physiology divided adaptation to cold into 4 groups (Máček, Radvanský, 2011)

• genetic (from the evolution point of view individuals living in colder climates are able to sleep in cold temperatures wearing fewer clothes and using fewer blankets that Central Europeans)
• acclimatization (acquired modifications in response to complex outside factors, such as seasonal and climatic changes)
• acclimatization (acquired modifications in response to the only environment factor (e.g. cold)
• adjustment – inhibited responses or reduced sensitiveness following repeated exposure to cold stimulus

Page 9

An organism tends to behave differently when exposed to higher altitudes. Training at altitude presents an effective means to enhance performance especially in endurance athletes.

The high altitude environment may be divided into three zones according to its altitude (Máček, Radvanský, 2011):

1. medium altitude 1.500-2.500 m above sea level
2. higher altitude 2.500-5.300 m above sea level
3. extreme altitude over 5.300 m above sea level

In this environment (Fig. 29) both the atmospheric pressure and partial oxygen pressure (PO2) tend to drop with rising altitude. With rising altitude the air temperature is reduced by 1°C for every 150 m of altitude irrespective of latitude. Latitude, however, tends to affect seasonal and daily temperature fluctuations (differences in the sun and in the shade).

Figure 29 External conditions in various altitudes

Alpine fresh air shows a reduced pressure of water vapours, the absolute humidity is likely to be extremely low in high altitudes. The combination of low relative humidity may be perceived as very uncomfortable. The air tends to be drier and thinner. The intensity of sunshine, especially its UV element rises, however. The intensity of UV radiation expands by 20-30% for every 1.000 m, these effects are multiplied by snow reflection. Also the intensity of cosmic rays grows (generation of oxygen radicals whose amount grows in proportion with a rising oxygen pressure). In higher altitudes lower gravitation and air flow may be observed.

The reduced partial pressure unfavourably affects both the transfer of oxygen from alveoli into capillaries of a small blood circulation (through diffusion) and the transport of oxygen to tissues. This results in the situation where the tissues are deprived of the adequate oxygen supply, hypoxia (Jančík et al., 2007) The high altitude environment causes the reduced haemoglobin affinity for oxygen which affects a sports performance.

Response of an organism to the high altitude environment

In the altitude of 2.500 m above sea level a decline in the supply of oxygen to tissues is not significant. Only 15% of those entering this level my show signs of acute altitude disease. (Máček, Radvanský, 2011)

Hypoxic conditions of the high altitude environment affect physiological responses of the organism. A diffusive gradient which plays an indispensable role in the exchange of oxygen between the blood and tissues is significantly disturbed. The percentage of haemoglobin saturated with oxygen is reduced. The organism is trying to avert these negative influences through activation of regulatory mechanisms and thus increase the oxygen supply. As a result hyperventilation occurs both under resting conditions and under workload, and deeper (enlargement of tidal, i.e. breathing volume- VT) and faster breathing (increase in breathing frequency -BF) appears. Regarding circulatory parameters both the heart rate (HR) and the cardiac output (Q) tend to increase. Openings of vascular capillaries increase dramatically preventing acute hypoxia. There follows a gradual decrease of the blood plasma volume resulting in the increased concentration of erythrocytes which in turn allows greater oxygen transfer and thus compensates for the reduced oxygen supply (Jančík et al., 2007)

The decline in bodily performance may well be connected to the reduction of VO2 max which drops in a linear manner with rising altitude, about 10% for 100 m (Máček, Radvanský, 2011, according to Wilmore, Costill).

Adaptation (acclimatization)

Adaptation of an organism to the high altitude environment is a long-term matter. It is a complex process spanning a few weeks, the speed of which depends on the altitude. There is a gradual increase in the capacity of the oxygen transporting system. More erythropoietin is released (EPO) which increases the generation of erythrocytes in the bone marrow. Thanks to this the level of haemoglobin which transports oxygen in the blood, is rising. In an organism there occurs a continual increase of mitochondria, myoglobin and enzyme activity. Vascularisation (growth of blood vessels into a tissue with the result that the oxygen and nutrient supply is improved) is strengthened. (Jančík et al., 2007, according to Havlíčková, 2004)

Recent studies do not confirm a significant improvement in performance in the lowlands following altitude training. Conditions in the medium and higher altitudes lead to dehydration and muscle atrophy.

To achieve overall improvement of performance current studies recommend training at lower altitudes alternated with stays at medium altitudes (to achieve an increase in erythrocytes).

Acclimatization

The duration of acclimatization varies depending on an individual in question and other factors such as the climbing speed, absolute height reached, relative height difference surpassed and the momentary health condition.

Medium altitude 1.500-2.500 m above sea level

The saturation of arterial blood with oxygen (SaO2) exceeds 90%, tissue oxygenation is not constrained. In the first days of the stay resting ventilation increases.

High altitude 2.500-5.300 m above sea level

2.500 m above sea level is the threshold altitude to trigger acclimatisation processes. SaO2 drops significantly under 90%. At this altitude complete and long-term acclimatization may be achieved. La Rinconada, Peru, a mining village is currently the highest permanent human habitation at an altitude of up to 5.100 m above sea level.

Extreme altitude over 5.300 m above sea level

Humans are not able to adjust to these altitudes and during longer stays the organism starts to waste away. Oxygenation is secured only by significant ventilation. Starting at an altitude of 6.000 anaerobic glycolysis and generation of lactate are inhibited. The oxygen saturation value on the peak of Mount Everest reaches about 50%.

Acclimatization progression

Acclimatization is divided into stages. Complete acclimatization to a certain altitude is indicated by the resumed (i.e. identical with original values) resting heart frequency measured on awakening in the morning. The duration of acclimatization varies depending on an individual in question and other factors such as the climbing speed, absolute height reached, relative height difference surpassed and the momentary health condition.

The following information shows approximate duration of acclimatization needed at different altitudes:

3.000 m – 2-3 days 4.000 m – 3-6 days

5.000 m – 2-3 weeks

Humans are not able to adjust to altitudes over 5.500 m (over this limit the decline of health and performance is inevitable despite maximum physical preservation). Adaptation mechanisms enable the organism to survive only a few days at such altitude. Adaptation to hypoxia includes changes in oxygen transportation into tissues and changes in its utilization in cells. Accommodation, i.e. the initial response in untrained individuals, takes effect in a few seconds to hours. The terms acclimatization and acclimation refer to changes taking effect in the course of days or months of the stay in a hypoxic environment (phenotypic adaptations which become reversible after return to normoxic conditions).

Acclimatization stages:

1. Latent phase – takes place during the first six hours after reaching a particular altitude, without symptoms of acute altitude disease (AAD)
2. Acclimatization – period of acclimatization acquisition accompanied by a substantial risk of acclimatization disorders (AAD)
3. Acclimatization – a period spanning 2-3 weeks during which a human becomes optimally adapted to an altitude and is capable to produce his/her maximum physical performance
4. Degradation (altitude deterioration) – accompanied by a decline in physical and mental functions

General rules of acclimatization

1. To stay overnight at the lowest possible altitude, climb in stages and stay overnight at an altitude lower than the one reached.
2. Every 500 m of covered altitude should be compensated by two nights spent at the same altitude. It is not advisable to stay overnight in a camp higher by more than 1.000 m during a single week.
3. To sleep with the upper part of the body slightly elevated, acclimatization may not be accelerated by any medicine.

Page 10

The composition of a human body may be considered from different perspectives. The human anatomy model (Fig. 30) divides the body into the following systems:

• muscular
• skeletal
• adipose tissue (body fat)
• the others (inner organs, etc.)

Figure 30 Body composition – anatomy model

The chemical (Fig. 31) model consists of:

• water
• glycogen
• fat storage
• proteins
• minerals (Ca, P, Mg, Cl, Fe, Cu, etc.)

The method most widely used in the Czech Republic for detection of body composition is the one according to Matiegka. First of all, height and weight of an individual are measured, then width and circumferential measurements are taken. A calliper (a measurement device for skin folds) is used to detect the value of body fat. Individual items (skeletal, muscular, fatty and the others) are calculated using formulas.

Figure 31 Body composition – chemical model

Other methods for detection of body composition:

• underwater weighing
• X-ray (DXA)
• plethysmography
• measurement of skin folds
• bioelectrical impedance (photo)

Body structure, somatotype

The optimal body structure presents an elementary factor in many sports. The body structure is characterized by somatic parameters (length, width, circumference, etc.) Sports activity may affect some width and circumferential parameters especially through the development of muscle mass and reduction of the fatty part.

The body structure is also defined by its somatotype. Various somatotypes may be suitable for various sport disciplines (Fig. 32, 33). The most frequently used method is that of modification of the Sheldon procedure further elaborated by Heath and Carter.

Under this methodology the somatotype consists of 3 components:

• endomorphic component
• mesomorphic component
• ectomorphic component

In sports we usually encounter a developed mesomorphic component indicating development of muscles and robustness of the skeletal frame.

Figure 32 Somatotype - males

Figure 33 Somatotype - females

The body size is given by its height, weight, and surface.

Page 11

A sports performance is affected by a number of factors including sex and age. The first significant stage of development of physical activities takes place during the first stage of human ontogenesis. During later life individual movement activities disappear and in the old age it is recommendable to carry out physical activities to keep healthy and fit.

Physiological specialties of the child's organism under workload

Apart from a calendar age there is also a biological age playing an important role in a sporting environment. This refers to a real development stage of the child's organism. Differences in the biological age may be of up to 3 years in some periods of life.

Proportional age is based on the relation between the development of body parameters (height, weight, circumference, width). The most accurate method to detect the maturity of the skeletal frame is the so called bone age (RTG image of wrist necessary). The bodily development in boys is completed around 18-20 years of age, in girls it is a bit earlier. In the toddler's age a movement should derive from spontaneous activity. A child should not be exposed to any sports activity as this could damage the movement apparatus not fully developed at the time. In human ontogenesis the process of growth and development is first completed in the brain which happens at the end of the preschool age (3-6 years) when a dramatic motoric development is initiated. In the younger school age (6-11 years) there occurs a smooth growth of all the organs. This period is characterized by the rapid development of coordination abilities, there is considerable potential for speed and movability. In the older school age (11-16 years) there is puberty. The development of physical and mental side continues up to the age of 17 in girls and a bit longer in boys. In this period the increase of sexual hormones shows in the increased muscle power. This period also provides the best conditions for the fastest and most effective process of motoric learning possible. The full physical development is reached at the end of youth (15-18 years). At this age humans can conduct their physical activities without restraint.

The size of the heart is directly linked with the body size which means children have a smaller heart than adults. This naturally means the child's body contains smaller volume of blood, children have smaller systolic volume. The higher maximum heart frequency in a child compensates only partially for lower systolic volume with the result that the maximum minute volume is smaller than in the equally trained adults.

Sexual differences in sport

The distinct differences between men and women may be found in the body organization. Men have a more significant muscle component than women while women are inclined to store more body fat than men. Differences in the physical performance first become apparent in the beginning of puberty. Male sexual hormones build up more muscle mass resulting in more significant muscle power. Women show smaller aerobic capacity, they switch to the anaerobic lactic way of energy production earlier than men. In women we encounter higher HF max and HF and Q values under submaximal workload. Under resting conditions women, however, tend to display lower Qs values, they have a smaller heart and smaller blood volume. Women have reduced vital lungs capacity, reduced breathing volume and minute ventilation.

Sports performance in women may be affected by the menstruation cycle which starts at about 13 years of age in non-sporting girls and later in sporting girls. Sporting women are likely to suffer from the lack of iron which may negatively impact the performance of endurance athletes especially.

At the beginning of pregnancy the performance of cardiovascular system grows which boosts the ability to deliver better endurance performance. Despite this trend pregnant women should not compete. Activities of moderate to medium intensity are recommended in this period. From the 5th month of pregnancy women are advised to interrupt training and resume it 6 weeks after giving birth if the delivery was a problem-free one. At this stage women are advised to resume low intensity training. Full intensity training is recommended 6 months after childbirth.

Page 12

Stress tests are used to assess the fitness in athletes or to diagnose physical activities. An athlete will usually undergo these tests in a specialized stress measuring laboratories. Field tests which are equally important are usually conducted under specific conditions for a sport discipline in question.

Equipment of a stress measuring laboratory

• ergometers (treadmill, bicycle ergometer, rowing ergometer, etc.)
• devices to measure circulation parameters (sport-testers, ECG, pressure metres)
• devices to measure ventilation parameters (spirometers, gas analyzers)
• dynamometers
• biochemical blood analyzers
• other (e.g. calorimeters)

Examples of stress protocols

Before a stress test is taken it is necessary to choose the right stress protocol (Fig. 34) which will further specify the intensity of workload, its duration, etc.

• single-grade stress test
• graded stress test
• graded test with pauses
• ramp
• continual
• combined

Figure 34 Basic protocols of ergometry

Anaerobic tests

Using anaerobic tests the level of anaerobic predispositions, i.e. speed-strength abilities is assessed. The most frequently used tests include:

Nejčastěji využívané anaerobní testy:

• Wingate tests
• jump ergometry (Bosco test)
• dynamometry

Wingate test

The test is conducted on the isokinetic cycle ergometer. The test duration is 30s (Fig. 35) during which an individual makes an absolute effort to push the pedals as fast as possible on a bicycle ergometer. The values assessed include: maximum performance achieved, total work and fatigue index. The test focuses on the ATP-AC system assessment and the LA system-speed-assessment.

Figure 35 Wingate test

Jump ergometry (Bosco test)

The test is carried out on the jump ergometer (a board acting as an electrical switch). The test duration is 10-60 s. Depending on the duration both explosive and endurance strength of the lower limbs may be measured. In the test speed of the active stage of take-off, the height of the jump, etc. are assessed.

Dynamometry

Muscle dynamometry is used to test strength predispositions. Isometric dynamometers test muscles in isometric contraction (muscle length does not change) and isokinetic dynamometers test muscles during a movement within a joint range. In addition to maximum power we may also watch the dynamographic curve showing power progression in time. On the dynamographic curve a moment of turning may be observed, etc.

Aerobic tests

Using aerobic tests the level of aerobic predispositions, i.e. endurance abilities are assessed. The most frequently used tests are:

• maximum oxygen uptake (VO2max)
• evaluation of anaerobic threshold (ANT)
• running (movement) economy
• The test of physical working capacity 170 (PWC 170)

The basic physiological factors constraining endurance performance include: maximum oxygen uptake (VO2max), the 'anaerobic threshold' value (ANT) and economy of movement (e.g. economy of

VO2max – maximum oxygen uptake

Average values of the population and average values for selected athletes shows Fig. 36.

Figure 36 Maximum oxygen uptake

ANT – anaerobic threshold

The issue of the anaerobic threshold is widely discussed nowadays. The previously used definition of the ANT read as follows: 'The anaerobic threshold is a divide between predominantly anaerobic and aerobic ways of energy production. It is a period of time characterized by the commencement of anaerobic glycolysis accompanied by the release of lactate into blood.'

The value of the 'anaerobic threshold' may be expressed in a number of ways, in training most commonly in % from HRmax. The ANT value may also be expressed in % derived from the VO2max detected in the maximum stress test. As it is not always easy to detect the ANT value, following are the examples of the threshold value assessment using the basic methods:

1. Lactate threshold – detection using the lactate curve (Fig. 37). Under the workload of rising intensity blood samples are taken to determine the lactate concentration in the blood. Based on these values a curve is drawn including a breakpoint when the volume of lactate in the body rises dramatically. The lactate threshold may be found between 2-8 mmol/l.

Figure 37 Lactate threshold


2. Ventilation threshold (ventilatory breakpoint) – threshold determined using ventilation parameters (most frequently minute ventilation). During a run of a rising intensity the values of ventilation parameters are recorded using the air analyzer (VE, VE/VO2, RER) – Fig. 38, 39). Based on the gathered data a graph is drawn and the breakpoint, in which an increase has been observed, is determined. The breakpoint may denote an increase on the ventilation curve or in oxygen equivalent.

Figure 38 Ventilation threshold



Figure 39 “Anaerobic threshold” determined from oxygen equivalent



Threshold determination using the ratio of the respiratory exchange ratio is carried out in a moment when the carbon dioxide output (VCO2) equals oxygen intake (VO2), RER = 1.

3. Circulatory threshold – determination of the anaerobic threshold using the Conconi test (Fig. 40). This is an indirect method through which we estimate the heart frequency curve. A tested person takes the Conconi test on a treadmill or outdoors. Every 200m is increased the running speed by 1 km/h. The initial speed is set in accordance with the person's fitness. The 'circulatory threshold' is determined in the moment of deflection, i.e. when the HR curve diverges from the linear curve.

Figure 40 Example of circulatory threshold determination (Novotný et al., 2006)

Economy of movement (running)

Using the Saltin test and the air analyzer we may determine the value of oxygen intake at various running speeds. Modification of the test shows Fig. 41.

Figure 41 Modification of the Saltin test to determine the economy of running

The PWC 170

Widely used in the Czech Republic the W170 test assesses the overall fitness of an individual. The test is conducted on the cycle ergometer. It aims to determine the workload in watts (W/kg) which a human is able to pedal at the HR value of 170 beats/min. The average values assessed in Czech women are approximately 1.8 W/kg (Placheta et al., 1999). The best male endurance athletes, especially road cyclists show values of up to 4 W/kg while women show 3.2 W/kg (Lipková, 2006).