Introduction to Exercise Physiology (external associations) PDF

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Class 2 - Exercise physiology - external associations....

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oxygen consumption

Maximum absolute (VO max) and relative (VO max / kg) oxygen consumption : an important indicator in exercise physiology 2

It is the amount needed to respond to the energy demand of a given activity. VO 2 increases linearly with load intensity and HR, up to a limit. It is measured in liters (L).

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In biomedical studies of exercise in athletes and in the population, it is important to perform a maximal cardiorespiratory exercise test (ergometry or functional ergospirometry) to determine VO 2 max and VO 2 max/kg, which will be explained in this chapter and in Chapters 4 and 13. As you know, success in endurance sports is related to: -At high values of VO 2 max and VO 2 max/kg, as well as at the efficiency of the anaerobic threshold. -The economy of the sporting gesture, such as the effectiveness of the stride for a runner or the stroke for a swimmer. -The ability to maintain a submaximal effort for a long time. VO 2 max/kg is a variable of great importance to health programs in the population in order to know cardiorespiratory fitness. There are circumstances that limit VO 2 in men, among which the following stand out: -The speed of nutrient transport to active tissues, which depends on cardiovascular and respiratory function. -The ability to use O 2 by active cells. -The diffusion capacity of O 2 in the lungs. -Inactivity, age, fitness and illness. There are different non-invasive methods to obtain VO 2 max directly (with the use of respiratory analyzers during stress tests, in laboratory and field conditions) and indirect (through laboratory testing with the ratio of the load used and its biological response). In field tests, from the speed performed at different distances, the absolute and relative VO 2 max is calculated as in the Cooper and Tokmakidis tests, among others. There are multiple protocols in laboratory tests to obtain VO 2 max, directly or indirectly. The consumption of 1 L of O 2 generates 5 kcal, with a perfect relationship between the O 2 consumed and the energy produced. Therefore, the greater the VO 2 , the greater the energy yield.

Maximum oxygen consumption or maximum aerobic power It is the measurement, in L/min, of the maximum O transport capacity of an individual's heart and lungs, as well as the capacity of the muscles to use and consume O . When VO max reaches its limits, a plateau occurs: despite increasing load, there is no increase in VO max. Under resting conditions, baseline O consumption is 0.25 L O /min; it is the same for sedentary individuals and for those who practice any type of sport. During light exercise, a normal person can triple it to 0.75 L of O / min. If the exercise is moderate or submaximal, it can be multiplied 8 to 12 times, that is, up to values of 2 to 3 L of O /min. The trained individual can reach up to 4 to 5 L/min. Higher capacity athletes can reach 6.2 L/min. The values decrease with age and increase with training. 2

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Maximum relative oxygen consumption It is the VO max per kg of weight, expressed in mL/kg/min. It is the most important biological indicator of the population's health and physical condition. In Chapter 15 we will look at various classifications for the different groups, by age and sex, according to the American College of Sport Medicine (ASCM). As an average, it is a little lower for women, 33 to 45 mL of O /kg/min, than for men, 42 to 52 mL of O /kg/min. It is an important indicator for high competition sport, especially for endurance sports. Figure 2.1 shows the relationship between the content of slow muscle fibers, or type l, and VO /kg, in different sports. There is a direct relationship between the two. 2

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Factors influencing VO max and VO max/kg The following factors influence VO max and VO max / kg: genetic, constitutional (body composition), sex, age, physical activity or sport, training level, environmental temperature, atmospheric pressure, health status, effort made during the test or test and ability and technique to perform the sporting gesture. 2

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Steady state, the deficit and debt O 2

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When a physical activity is carried out economically, in which there is a balance in the energy expenditure/production ratio, the work of the aerobic metabolism is maintained without exceeding the anaerobic threshold (3.4 mmol/L of lactic acid). When the intensity of the activity exceeds the level of lactic acid production, it depends on the anaerobic metabolism to respond to the O 2 deficit , which finally leads to an O 2 debt .

steady state Balance exists between the energy required by working muscles and the rate of ATP production. The following variables are kept constant: HR, RR, BP, DC, respiratory volume per minute, VO 2 max/kg, lactate, sports gesture, etc. In high-performance sports, especially in endurance sports, it is important to work at a high percentage of VO 2 max in steady-state conditions, since you are working with high efficiency, not using an energy source at that time. important of anaerobic character.

oxygen deficit It is the difference between the O 2 requirements and the actual amount supplied and consumed. Occurs at the beginning of a given job (even very light). Energy is provided by anaerobic metabolism. Sometimes the O 2 deficit is maintained all the time during intense events of short duration, such as 100 to 800 m dash in athletics and between 50 and 200 m in swimming, etc. In endurance sports at final acceleration, for better timing and sporting success, anaerobic energy is needed.

Oxygen debt It is defined as the amount of O 2 consumed after exercise, above the baseline consumption prior to sports practice. It reflects the body's payment, through aerobic metabolism, for the energy expenditure that accumulated during work (which was facilitated by the anaerobic route to respond to the deficit), as well as for endocrine-metabolic, cardiorespiratory and neuromuscular adjustments during recovery. Debt repayment is quick at first and then slower. The maximum O 2 debt of each individual limits the performance of the exercise as it is a factor that conditions the onset of fatigue. Physical training increases the amount of debt before fatigue sets in. There is a marked difference in O 2 deficit and debt in light and moderate exercise (Figure 2.2) and in intense exercise (Figure 2.3), being, in

the latter case, more marked by the need for anaerobic metabolism to respond to energy needs of this type of exercise. For this reason, the organism's full recovery to offset the O2 debt would be slower in intense activity. Figure 2.4 shows the same situation.

Dynamic exercise intensity rating Table 2.11 shows the relationship between absolute and relative VO 2 max with respect to high performance athletes, as well as individuals trained for health purposes and sedentary people with certain diseases and risk factors for non-communicable chronic diseases . A simple method to measure work intensity is to obtain HRmax and its subsequent relationship with VO 2 max, since, as previously seen, there is a correlation of linear increase in both variables expressed as a percentage. This correlation decreases from 90% of VO 2 max. The variables are related to the perception of effort according to the Borg scale (Table 2.2).

How can we measure a person's maximum heart rate? Both for high-performance sports and for population-oriented health programs, we can use the following formula: maximum heart rate HRmax = 220 - age For example, the HRmax of a 22-year-old athlete is 198. Knowing the HRmax allows the sports physician, coach, physical education teacher or physical trainer to plan the HRmax intensity percentage range, that is, the bpm range before a given exercise load, depending on the development of different individualized goals in competitive sport or physical activity programs for health. For elderly people and for people with illnesses, exercise should be prescribed by the doctor. The anaerobic threshold of a normal individual (3 to 4 mmol/L of lactic acid), in good physical condition, should be between 75 and 85% of VO2max. A high-level, well-trained athlete may have his LA at 90% of HRmax or slightly higher. Table 2.12 shows the Pollock and Wilmore classification of relative intensity, an easy and complete way to assess the biological response to the training load received, as well as from a psychophysiological point of view, by including the

degree of perceived exertion by Borg. All of this can be related to other biological responses to training loads from a biochemical point of view, such as lactic acid, urea, etc.

Importance of anaerobic metabolism In competitive sport, training is very important, in any sport, through anaerobic metabolism, being more prevalent in sports that depend on speed and/or strength. As mentioned in Chapter 1, the main sources are the lactic anaerobic pathway, via CP, and the lactic anaerobic glycolytic pathway, with the accumulation of lactic acid.

Anaerobic capacity It is the maximum amount of ATP resynthesized by anaerobic metabolism (of the whole organism) during a specific type of shortterm maximal effort (Green, 1994). That is, if depletion occurs in less than two minutes, the amount of ATP provided by anaerobic metabolism is unlikely to be maximum. The term anaerobic capacity indicates the maximum ATP that anaerobic metabolism can provide.

anaerobic power It is the maximum speed at which anaerobic metabolism can resynthesize ATP during a shortterm maximal effort.

Alactic anaerobic capacity It is the amount of ATP that can be resynthesized by anaerobic metabolic processes at the expense of CP, without the production of lactate. lactic anaerobic capacity It is the amount of ATP that can be resynthesized via the glycolytic pathway, in a maximum intensity effort until exhaustion, with the production of lactate. Lactic acid metabolism It is of great importance, as it allows the muscle to obtain energy very quickly and without depending on the O transport mechanisms . The total amount of energy produced in this pathway (anaerobic glycolytic) is less than when there is complete oxidation. Lactate accumulation in muscle is a fatigue-inducing mechanism. 2

Anaerobic threshold: an important indicator in high performance It is the percentage of VO 2 max usable over an extended period. This threshold is exceeded when working at a higher intensity, which results in rapid accumulation of lactic acid and loss of the anaerobic threshold. The threshold can also be exceeded when working hours are too long, depleting energy reserves. LA is the point of intensity at which lactate begins to accumulate, with its concentration of approximately 3 and 4 mmol / L. This threshold defines two zones, one lower and one higher. It is an important indicator of efficiency in high performance sports, even above VO 2 max/kg. Working at a high intensity in the LA of the percentage of VO 2 max guarantees a higher speed, without the accumulation of lactate and with a delay in the appearance of fatigue. The steady state can be found within the LA. The lower limit of this threshold is the aerobic threshold, with approximate values between 1.5 and 2.9 mmol/L. The AT of a healthy, active person is between 75 and 85% of VO 2 max. In an athlete with a high level of endurance modalities 90% of VO 2 max can be found .

Ventilation and energy metabolism during exercise We call the oxygen ventilatory equivalent (VE/VO 2 ) the ratio between the volume of air ventilated (VE) and the amount of O 2 consumed by tissues (VO 2 ), which indicates the O 2 saving . Under resting conditions, VE/VO 2 can fluctuate between 23 and 28 L of air per L of O 2 consumed. During light-intensity, steady-state exercise, ventilation accurately reflects the rhythm of energy metabolism. The maximum tolerable ventilatory voltage point is the moment when ventilation increases abruptly, although O 2 consumption does not. This increase reflects the need to eliminate excess CO 2 . The respiratory equivalent of O 2 (VE / VO 2 ) is one of the respiratory variables used to determine the aerobic threshold and the anaerobic threshold.

Criteria for determining ventilatory thresholds

Respiratory physiology reveals aerobic and anaerobic ventilatory thresholds through increasing loads (progressive test) in laboratory equipment using an exercise bike, treadmill or remoergometer, etc., always coupled to respiratory gas analyzer equipment with electrocardiographic monitoring . It is a non-invasive and maximal test (although submaximal can be given some value) and is mainly used in competitive sports. Different respiratory variables are taken into account during physical effort, such as O 2 consumption, CO 2 consumption , expiratory volume, O 2 respiratory equivalent, CO 2 respiratory equivalent , O 2 pressure end-expiratory air (PET O 2 ), CO 2 pressure of end-expiratory air (PET CO 2 ), respiratory quotient and maximum O 2 consumption (VO 2 max), which are related to cardiovascular variables during rest , exercise and recovery, such as HR, BP and electrocardiography. Sometimes, blood lactic acid is measured during different loads, according to the applied methodology, in order to relate the biochemical results with the respiratory and cardiovascular ones. From all these variables we obtain others, such as VO 2 max/kg, O 2 pulse /VO 2 max/HRmax, double product, etc. When the athlete is submitted to a progressive load test (1 to 4 minutes in each increasing load according to the methodology), a series of changes in the respiratory variables occur, such as: - Up to 40 to 50% of VO 2 max: aVEVE, decreasesPET O 2 , increasesPET CO 2 , decreasesVE / VO2 - Between 50 and 70% of VO2max: Increase increaseVE, decrease PET O 2 , increase PET CO 2 , increaseQR - Above 70% of VO 2 max: Increase Increase Increase VE, Increase PET CO 2 , Increase VE/VO 2 , Increase QR, Decrease PET O 2 When the intensity of the maximum effort exercise increases with each increased load, we observe modifications, such as: -The VO 2 increases linearly until reaching a maximum value, where it remains (VO 2 max) in the form of a plateau. -EV and VCO 2 increase linearly to a critical point (transition zone), from which the increase is greater than that of VO 2 . -VE/VO 2 and O 2 pressure of PET O 2 decrease in the first loads, and then progressively increase.

At the biochemical level, the modifications in a progressive test obey the muscular imperative to obtain energy to perform the muscular contraction and, therefore, the movement. The routes of prolonged use of submaximal energy go from the initial use of phosphogenics, passing through anaerobic glycolysis, through aerobic glycolysis and the use of fatty acids as the main source for obtaining energy. The moment when the energy provided by aerobic glycolysis crosses with that provided by the oxidation of fatty acids has recently been called cross-over (Brooks and Mercier, 1994). During the time of an exercise test (20 to 25 minutes), the cross-over occurs at 60 to 70% of VO 2 max. If exercise proceeds to maximum intensities, massive recruitment of type II fibers begins, anaerobic glycolysis increases, and an increase in lactic acid production occurs. The buffering of the formed lactic acid is carried out predominantly by the bicarbonate system: Lactic acid + sodium bicarbonate = sodium lactate + carbonic acid Carbonic acid quickly changes to carbonic anhydride and water by the action of carbonic anhydrase. Increased production of CO 2 and, therefore, of LV has been classically described as the biochemical basis for respiratory changes in this type of exercise testing (Wasermann, 1973). There are different methods for obtaining aerobic and anaerobic ventilatory thresholds. Next, the Davis method (Córdoba, 1985) will be discussed.

Ventilatory threshold (VT1) - aerobic threshold -First non-linear increase in ventilation. -Increase in VE/VO 2 without a simultaneous increase in VE/VCO 2 . -Elevation of PET O 2 without a reciprocal reduction of PET CO 2 . Blood lactate production is between 1.5 and 2.9 mmol/L.

Ventilatory threshold (VT2) - anaerobic threshold -Second disproportionate and non-linear increase in ventilation.

-Nonlinear increase in VE/VO 2 with simultaneous increase in VE/VCO 2 . -Elevation of PET O 2 with a reciprocal reduction of PET CO 2 . Blood lactate production is between 3 and 4 mmol/L. In Chapter 13 we will cover with more precise examples the best way to determine the aerobic and anaerobic thresholds, also taking into account other important variables, such as QR, HR during each intensity stage in the laboratory test, work intensity, percentages HRmax and VO 2 max, the sport modality and the athlete's level, the degree of perceived exertion and, when possible, the blood lactate. In Chapter 13 we will also discuss the interpretation of the maximum ergospirometry test, citing examples and recommendations to the trainer. We must be clear about the concepts of maximal effort tests from a respiratory and cardiovascular standpoint. It should be considered that the ideal is to perform the test up to 100% of HRmax. They could also be criteria for completing the test: major changes in the electrocardiogram (ST segment depression, major ventricular extrasystoles), severe hypertensive response to exertion, chest pain, etc.

Criteria for maximal exercise tests in ergospirometry -Obtain 100% of HRmax -Plato on the VO 2 curve -VO 2 max x peak VO 2 -Respiratory quotient > 1.1 (1.18 and 1.19) Table 2.13 shows the classification of respiratory thresholds based on the percentage of VO 2 max reached at each threshold. This classification is for high performance athletes. In the normal population practicing aerobic physical activity (cardiorespiratory fitness), achieving a normal or satisfactory assessment in this classification can be considered good or very good depending on age and health status. In this classification, the sport modality, individual characteristics of the athlete, age and sport level, stage of training, previous studies about him and his sport, etc., must be taken into account. The most talented and best-trained sportsmen in endurance modalities have more efficient anaerobic thresholds (> 90%). In Chapters 6 and 7 the importance of the anaerobic threshold will be addressed. Physiological responses above the anaerobic ventilatory threshold: metabolic

acidosis, decreased aerobic endurance, acceleration of glycogen utilization and anaerobic ATP regeneration (depletion of glycogen stores and lactic acid accumulation), reduced O 2 extraction , state delay stable VO 2 , increased CO 2 production , increased expiratory volume, increased catecholamines and the double cardiovascular product, and hemoconcentration (due to increased intracellular fluid).

lactic threshold In performing the progressive test, a series of metabolic processes occur observable in serial blood lactate samples. The quantities obtained obey the interaction between the produced and the purified lactate (Broocks, 1985). The increased production of lactate by the recruitment of fast muscle fibers, together with the decrease in blood flow to the liver and kidneys (essential organs for its clearance) and the difficulty of the muscles that perform the exercise to extract and oxidize lactate, are the causes of exponential increase in lactate at a given time, which is called the lactic threshold (LT). The production of lactate drops, since its accumulation produces a metabolic acidity, causing fatigue in the biochemical and respiratory levels, which does not allow the continuation of such an intense exercise. Figures 2.5 and 2.6 show, respectively, a scaled lactate test, as well as the interpretation of the lactate curve with the corresponding increase in lactic acid from the increase in exercise intensity. Figure 2.5 shows the relationship between bloo...