Exercise physiology

Exercise physiology Recommended literature: Wilmore, J. H., & Costill, D. L. (1994). Physiology of sport and exercise. Champaign, IL: Human Kinetics. Åstrand, P.-O., Rodahl, K., Dahl. H. A., & Strømme, S. B. (2003). Textbook of Work Physiology: Physiological Bases of Exercise (4th ed.). Champaign, IL: Human Kinetics. Brooks, G. A., Fahey, T. D., & White, T. P. (1995). Exercise physiology: human bioenergetics and its applications (2nd ed.). Mountain View, CA: Mayfield Publishing Company. Sharkey, B. J. (1990). Physiology of fitness. Champaign, IL: Human Kinetics.

Exercise => causes the changes in human body A) Acute response to one bout of exercise – e.g. ↑ heart rate (HR), ↑ body temperature (HR) B) Chronic adaptation to repeated bouts of exercise - e.g. ↓ HR at rest and ↓ HR at exercise (same intensity)

Změny vybraných parametrů

- decrease of ATP, increase of ADP Exercise => causes the changes in human body A) Acute response to one bout of exercise – e.g. ↑ heart rate (HR), ↑ body temperature (HR) B) Chronic adaptation to repeated bouts of exercise - e.g. ↓ HR at rest and ↓ HR at exercise (same intensity) Muscle activity requires energy. During exercise are energy demands enhanced. - decrease of ATP, increase of ADP Muscle contractile work = transforming chemical energy into kinetic (mechanical) energy

Energy metabolism A) Anabolism - creation of reserve (carbohydrate, fat, proteins) B) Catabolism – release of energy (glycolysis, lipolysis) hydrolisis ATP ADP + P + E phosphorylation ATP – adenosine thriphosphate - common energy “currency” ADP – adenosine diphosphate P - phosphate E - energy (e.g. for muscle contraction)

Energy metabolism Energy sources 1] Polysaccharides simple sugars glucose (glycogen) 2] Fats (triglycerides) fatty acids (FFT) and glycerol 3] Proteins amino acids

Energy metabolism Glucose is the only one that can be broken down anaerobically and aerobically as well. Anaerobic glycolysis blood plasma membrane cell plasma G G G – 6 - P Glycogen (GG) 2 ATP (G) 3 ATP (GG) pyruvic acid lactic acid

Energy metabolism Aerobic glycolysis pyruvic acid (pyruvate) cell plasma mitochondrial membrane mitochondrion Acetyl CoA NADH (nicotinamide adenine dinucleotid) and FADH Citric acid cycle CO2

Energy metabolism oxidative phosphorylation – in mytochondrion (electron transport chain) NADH + O2 + 3ADP 3ATP + NAD + H2O 1 NADH=3 ATP FADH + O2 + 2ADP 2ATP + FAD + H2O 1 FADH=2 ATP

Energy metabolism From one molecule G GG Anaerobic glycolysis 2 ATP 3 ATP Aerobic glycolysis 36 ATP 36 ATP Total glycolysis 38 ATP 39 ATP Glycogen reserves are in muscle cells (500 g) and in liver (100 g). - From 1.500 to 2.500 kcal. 1 calorie (cal) is the amount of the energy increases the temperature of 1 gram H2O from 14.5ºC to 15.5ºC.

Hormone-sensitive lipase Energy metabolism Fat - triglyceride = FFA (free fat acids) + glycerol in subcutaneous tissue (141 000 kcal). Adipose tissue reduction Glucose metabolism NADH and FADH triglyceride FFA + Glycerol Hormone-sensitive lipase Beta oxidation Acetyl CoA NADH and FADH Citric acid cycle CO2

Energy metabolism FFA proteins anaerobic aerobic Glucose pyruvate Acetyl CoA and/or lactic acid Citric acid cycle NADH and FADH Electron transport chain plasma membrane

Energy metabolism Anaerobic metabolism Anaerobic metabolism only carbohydrate increases when lack of O2 and not enough time lower amount of ATP, but very fast and huge in short time production of lactic acid Anaerobic metabolism carbohydrate, fats, proteins enough of O2 higher amount of ATP, but slower Note: proteins are not very important sources of energy (5-10%). Amino acids are preferabely used as a building matters for muscles, hormones, etc.

Energy metabolism ATP ADP + P + E hydrolisis ATP ADP + P + E phosphorylation ATP is only the one immediate source of energy for muscles work, etc. Other ways of the creation (phosporylation): ATP + C ADP + CP(creatine phosphate) ATP + AMP ADP + ADP

Zones of energy supply Anaerobic free of lactic acid Anaerobic with lactic acid Aerobic free of lactic acid

Total energy expenditure - s trváním pokles (?Havlíčková et al, 1991)

Dominant way of restoration of ATP is oxidative phosphorylation Acute reaction of the body (neurohumoral controlled) for increase in supply of working muscles by energy sources and O2 increase glucose in blood (from liver glycogen) activation of FFA (activation of hormone sensitive lipase)

Mechanism of energy release in dependence on intensity VO2max Anaerobic threshold NOTE: Ideal model Aerobic threshold REST aerobic anaerobic

exercise intensity % VO2max Sources of energy by increasing exercise intensity energy expenditure kJ/min RQ carbohydrates = 1 RQ = CO2 O2 1 g = 4,1 kcal RQ fats = 0,7 glycogen 1 g = 9,3 kcal fats glucose (Hamar & Lipková, 2001) exercise intensity % VO2max

more O2 Sources of energy by increasing exercise intensity CO2 - expired RQ = CO2 O2 O2 - inspired RQ – respiration quotient – ratio between CO2 and O2 RQ carbohydrates = 1 = 1 l CO2/1 l O2 more O2 RQ fats = 0,7 = 0.7 l CO2/1 l O2 RQ normal (mixed) = 0,82

Lipids (FFA) more energy (1 g = 9,3 kcal) need more O2 (EE = 4,55 kcal) use while enough of O2 (at rest, low intensity of exercise)

Lipids (FFA) EE – energetic equivalent more energy (1 g = 9,3 kcal) need more O2 (EE = 4,55 kcal) use while enough of O2 (at rest, low intensity of exercise) EE – energetic equivalent – shows amount of energy released while applied 1 liter of O2 on carbohydrate or on FFA

Lipids (FFA) Carbohydrates more energy (1 g = 9,3 kcal) need more O2 (EE = 4,55 kcal) use while enough of O2 (at rest, low intensity of exercise) Carbohydrates less energy (1 g = 4,1 kcal) need less O2 (EE = 5,05 kcal) use while not enough of O2 (higher intensity, and anaerobically as well) small amount is always use at rest

exercise intensity % VO2max Sources of energy by increasing exercise intensity energy expenditure kJ/min RQ carbohydrates = 1 RQ = CO2 O2 1 g = 4,1 kcal RQ lipids = 0,7 glycogen 1 g = 9,3 kcal fats glucose (Hamar & Lipková, 2001) exercise intensity % VO2max

Wasserman scheme of transport O2 a CO2 Muscle work Transport O2 and CO2 Ventilation Mito- chon- drion O2 AIR muscles cardiovascular s. lungs CO2 (Wasserman, 1999)

The more O2 is delivered to working muscle, the higher aerobic production of energy (ATP) Better endurance performance, smaller production of lactic acid while the same speed of run, longer lasting exercise, etc.

Wasserman scheme of transport O2 a CO2 Muscle work Transport O2 and CO2 Ventilation Mito- chon- drion O2 AIR muscles cardiovascular s. lungs CO2 (Wasserman, 1999)

VO2 = Q × a-vO2 Fick equation: × VO2 – oxygen consumption [ml/min] SV × HR VO2 – oxygen consumption [ml/min] Q – cardiac output [ml/min] a-vO2 – arteriovenous oxygen difference SV – stroke volume [ml] HR – heart rate [beet/min]

a-vO2 – arteriovenous oxygen difference

DA-V – arteriovenous oxygen difference difference in the oxygen content of arterial and mixed venous blood the value tells about the amount of oxygen used by working muscles depends on the muscle ability to absorb and use the O2 from blood (perfusion, amount of capillary, mitochondrion, number of working muscles, etc.) - at rest 50 ml O2 from 1 L of blood - during exercise 150-170 ml O2 1 L of blood (100 ml krve is saturated by 20 ml O2) (1 L of blood is saturated by 200 ml O2)

1 L of blood is saturated by 200 ml O2 To ensure during exercise: ↑BF (breathing frequency, rate) - from 12-16 breath/min up 60 (70 and more) ↑TV (tidal volume) from 0.5 L up 3 L Minute ventilation (VE) = BF × TV - at rest 6 L/min = 12 × 0.5 - during maximal exercise 180 L/min = 60 × 3

. VO2 = Q × DA-V Q = HR × SV rest: SEDENTARY 4,9 L = 70 beat/min × 70 ml rest: TRAINED 4,9 L = 40 beat/min × 120 ml In work: increase of HR and SV - ↑ Q SV increases till HR 110–120 beet/min (from 180 beet/min decreases) - HRmax = 220 - age

. rest: VO2 = Q × DA-V VO2 = 4,9 L of blood × 50 ml O2 Q = HR × TV rest: SEDENTARY 4,9 L = 70 beat/min × 70 ml rest: TRAINED 4,9 L = 40 beat/min × 120 ml rest: VO2 = 4,9 L of blood × 50 ml O2 VO2 = 245 ml/min human (70kg): 245 : 70 = 3,5 ml O2/kg/min (1MET)

. VO2 = Q × DA-V Q = SF × SV 20 L = 200 beat/min × 120 ml Max. exercise: SEDENTARY 20 L = 200 beat/min × 120 ml Max. exercise: TRAINED 35 L = 200 beat/min × 175 ml

. VO2 = Q × DA-V Max. exercise: VO2max= 20 L of blood × 157 ml O2 SEDENTARY: VO2max= 20 L of blood × 157 ml O2 VO2 max= 3140 ml/min 70 kg human: 3140 : 70 = 45 ml O2/kg/min (13 METs)

. VO2 = Q × DA-V Max. exercise: VO2max= 35 L of blood × 170 ml O2 TRAINED: VO2max= 35 L of blood × 170 ml O2 VO2 max= 5950 ml/min 70 kg human: 5950 : 70 = 85 ml O2/kg/min (25 METs)

Definition and explanation of VO2max is maximum volume of oxygen that by the body can consume during intense (maximum), whole body exercise. - expressed: - in L/min - in ml/kg/min - METs 1 MET - resting O2 consumption (3.5 ml/kg/min) 10 METs = 35 ml/kg/min 20 METs = 70 ml/kg/min

Importance of VO2max Higher intensity of exercise Higher energy demands (ATP) Increase in oxygen consumption Lower VO2max = less energy = worse achievement

Importance of VO2max During endurance activity is being ATP resynthesized mainly aerobically from lipids and carbohydrates. The more is O2 supplied to working muscles, the more higher is an amount of aerobically produced energy. It means higher speed of running, latest manifestation of fatigue, etc. It shows the capacity for aerobic energy transfer.

Decreases with age. Lower in female. Average values of VO2max Average (20/30 years) not trained: - female 35 ml/kg/min - male 45 ml/kg/min Trained: to 85 ml/kg/min (cross-country skiing) Decreases with age. Lower in female.

Average values of VO2max

Limitation factors of VO2max Muscle work Transport O2 and CO2 Ventilation O2 AIR muscles cardiovascular s. lungs CO2 (Wasserman, 1999)

Limitation factors of VO2max 1) Lungs – no limitation factor 2) Muscles – is limitation factor 3) Cardiovascular system – dominant limitation factor

Wasserman scheme of transport O2 a CO2 Muscle work Transport O2 and CO2 Ventilation Mito- chon- drion O2 AIR muscles cardiovascular s. lungs CO2 (Wasserman, 1999)

VO2max = Qmax × DA-Vmax On increase of VO2max participate: Increase of DA-Vmax – shares on increase about 20% Increase of Qmax – shares aboout 70 - 85%

Influence of the gender, health condition, age Heredity – the increase of VO2max by training only to max. 25% Gender – in female lower muscle mass, lover hemoglobin Age – decrease of active body mass, activity of enzymes…

exercise intensity % VO2max Sources of energy by increasing exercise intensity energy expenditure kJ/min RQ carbohydrates = 1 RQ = CO2 O2 1 g = 4,1 kcal RQ lipids = 0,7 glycogen 1 g = 9,3 kcal fats glucose (Hamar & Lipková, 2001) exercise intensity % VO2max

VO2max [ml/kg/min] 45 AT 50-60% VO2max 3,5 exercise intensity (speed, load, etc.)

AT (aerobic threshold) - exercise intensity, when „exclusive“ aerobic covering ends. exercise intensity, from which anaerobic covering starts and lactate is being produce level of lactate: 2 mmol/L of blood

VO2max [ml/kg/min] plateau 45 AnT 70-90 % VO2max AT 50-60 % VO2max 3,5 exercise intensity (speed, load, etc.)

AnT (anaerobic threshold) - exercise intensity, when anaerobic covering exceed aerobic. - exercise intensity, when dynamic balance between production and breakdown of lactate is disturbed level of lactate: 4 mmol/L of blood and is increasing (onset of blood lactate accumulation). at about approximately 8 mmol/L o blood is impossible to continue in exercise (trained even 30 mmol/L of blood)

AnT (anaerobic threshold) - can be estimate from VO2max: AnT = VO2max/3,5 + 60 AnT = 35/3,5 + 60 AnT = 70 %VO2max 1 MET 60 % of VO2max - AT

VO2max [ml/kg/min] 45 AnT 70-90 % VO2max AT 50-60 % VO2max 3,5 exercise intensity (speed, load, etc.)

lactate energy sources fiber type VO2max [ml/kg/min] onset of lactate accumulation – ↑ pH 45 fat < sugar AnT 70-90 % VO2max 4 mmol/L I., II. a, II. b L is oxidized (heart ,not working muscles) I., II. a 2 mmol/L fat = sugar AT 50-60 % VO2max fat > sugar I. 3,5 ? 1,1 mmol/L exercise intensity (speed, load, etc.)

(Hamar & Lipková, 2001)

Exercise intensity during endurance activity (>30 minutes) can not be above AnT. Before start of exercise - increase in O2 consumption (emotions, reflexions) 2) Initial phase of exercise (till 5 minutes) - rapid increase in the oxygen consumption Steady state - balance between the energy required by working muscles and the rate of ATP produced by aerobic metabolism - O2 is almost constant - lactate level is constant - HR is in the range ±4 beats (real steady state)

VO2max [ml/kg/min] O2 deficit AnT 3.5 Time [min] 5 30 before start initial phase steady state

Oxygen deficit Insufficient supply of working muscles with O2, at the beginning of exercise (slower ↑ SF and SV, BF and TV). disbalance between O2 demands and supply leads to use of anaerobic metabolism – production of LACTATE ( ↑ H+ – metabolic acidosis – death point). when O2 demands ensured – second breath after termination of exercise the increased O2 consumption persists = oxygen debt

VO2max [ml/kg/min] O2 deficit O2 debt AnT 3.5 Time [min] 5 30 before start initial phase steady state

Oxygen debt synthesis of ATP and CP resynthesis of lactate (back to glycogen in the liver, and oxidation by muscles and myocardium) - acceleration of release of lactate from muscles and better blood perfusion of muscles resynthesising lactate, is possible by low intensive exercise: (till 50 % VO2max – below AT) recovery of myoglobin, hemoglobin, hormone, etc. the major part (till 30 min), mild oxygen debt can persist 12-24 hours.

VO2max [ml/kg/min] false steady state - above AnT major O2 debt AnT 3.5 Time [min] 5 25 before start initial phase steady state

VO2max [ml/kg/min] smaller O2 debt AnT AP 3.5 Time [min] 2 30 before start initial phase steady state

oxygen consumption (L/min) trained - steady state is reached earlier sedentary - steady state is reached latter rest exercise time (min) (Hamar & Lipková, 2001)

Practical importance of VO2max VO2max = 70ml/kg/min AnP = VO2max/3,5 + 60 80% VO2max = 35 ml/kg/min 70% male A female

Practical importance of VO2max VO2max = 70ml/kg/min VO2max = 70 ml/kg/min 90% 80% male A male B

Critical parameter of endurance abilities is not VO2max, but AnT. However VO2max is conditional parameter of AnT.