Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University1 Energetic metabolism Physiology of Exercise Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University2 Energetic metabolism = summary of all chemical (and physical) processes included in: 1. Production of energy from internal and external sources 2. Synthesis and degradation of structural and functional tissue components 3. Excretion of waste products and toxins from body Metabolic speed: amount of energy released per unit of time Calorie (cal) = amount of thermal energy, necessary for warming up 1g of water for 1°C, from 15°C to 16°C Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University3 SACCHARIDES LIPIDS PROTEINS ENERGY INPUT = ENERGY CONSUMPTION MECHANIC WORK SYNTHESIS MEMBRANE TRANSPORT PRODUCTION AND TRANSMISSION OF SIGNALS HEAT PRODUCTION DETOXICATION DEGRADATION Muscle contraction Movement of cells (flagella), organelles Energetic stores production Tissue growth Essential molecules production Minerals Organic substances AA Electrical Chemical Mechanical Body temperature control Ineffective chemical reactions Urine production Conjugation Oxidation Reduction Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University4 I. thermodynamic law: At steady state, input of energy equals to its expenditure Input stores Expenditure of energy = external work + energy stores + heat Intermediate stages: various chemical, mechanical and thermal reactions Energy intake (input) Saccharides, lipids, proteins Burning releases: 4.1kcal/g, 9.3kcal/g, 5.3kcal/g (4.1 in body) 1kcal=4184J Conversion of proteins and saccharides to lipids – effective storage of the energy Conversion of proteins to saccharides – need of „fast“ energy BUT: there is no significant conversion of lipids to saccharides Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University5 Energy output 1. At rest: basal metabolism; 8 000 kJ / day; 200-250 ml O2/min; directly depends on body mass and surface; decreases with age; increases with ambient temperature; decreases by 10-15% during sleep; genetically determined 75%BM 2. After meal: slight increase in energetic output – specific dynamic effect – e.g. for glycogen formation 7%BM 3. In sitting position: spontaneous physical activity 18%BM 4. Facultative thermogenesis: non-shivering 5. During exercise: energetically most demanding; individual; changes according to season Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University6 Transport of energy among organs Adipose tissue Muscles Liver Triglycerides Free FA FA CO2 Muscle work Lactate Lactate Pyruvate Glucose Glucose ATP H+ Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University7 • Energy stores: ATP, creatinphosphate, GTP, CTP (cytosin), UTP (uridin), ITP (inosin) • Macroergic bond – 12kcal/mol • Efficiency is not 100% - 18kcal of substrate needed for 1 bond in ATP • Daily: 63 kg of ATP (128mol) • Glycolysis: only short-lasting source of energy (2 pyruvates – only approx. 8% of glucose energy); supply of glucose is limited, lactate RESPIRATORY QUOTIENT RQ = VCO2 : VO2 Saccharides: RQ = 1 Lipids: RQ = 0.7 Proteins: RQ = 0.8(per unit of time, at steady state) R – ratio of respiratory exchange (no steady state!) Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University8 Storage and transport of energy • Both input and output of energy are irregular – necessity of storage • 75% of stores: triglycerides (9kcal/g) in adipose tissue (10-30% of body mass), lasts up to 2 months ; source – dietary FA and esterification with a-glycerolphosphate or synthesis from acetylCoA (from glycolysis) – saccharides are converted to more effective store of energy = lipids • 25% of stores: proteins (4kcal/g); conversion to saccharides (gluconeogenesis during stress); adverse effects on organism • Less than 1% of stores: saccharides (4kcal/g) as glycogen; important for CNS!!! and short-term enormous exercise; ¼ of glycogen stores in liver (75-100g), rest in muscles (300-400g); liver glycogen – glycogenolysis – release of glucose; muscle glycogen – used only in muscles (no glukoso-6- phosphatase) • Gluconeogenesis: from pyruvate, lactate and glycerol and AA (except of leucin);NO from acetyl-CoA • Storage and transport of energy requires input of other energy: 3% from original energy – lipids (triglycerides to adipose tissue), 7% - glucose (glycogen), 23% - conversion of saccharides to lipids, 23% - conversion of AA to proteins or glucose (glycogen). Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University9 Direct calorimetry = measurement of energy released by burning of diet out of body (oxidation of compounds in a calorimeter) 1. Caloric bomb 2. Whole-body calorimeter (for laboratory animals, for humans) Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University 10 Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University11 Indirect calorimetry • Amount of consumed O2. • Amount of energy released for 1mol of consumed O2; differs according to type of oxidized compound (the effect of diet composition) Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University12 Factors affecting (basal) metabolism • Height, weight, body surface • Gender • Age • Body temperature • Emotional status • High or low ambient temperature (the dependence is expressed as a U curve) • Thyroidal status • Plasmatic level of catecholamines • Muscle work (before and/or during measurement) • Food intake (before measurement) Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University13 Work (physical activity, exercise) Source: www.freepik.com. Photos created by freepik and standret Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University14 Skeletal muscle ̶ Contraction: isometric (static work) vs. isotonic (dynamic work) ̶ Blood flow depends on muscle tension ̶ Metabolic autoregulation: ↓pO2; ↑pCO2; ↓pH; ↑K+; ↑local temperature ̶ Metabolism: aerobic vs. anaerobic ̶ Muscle spindles – muscle tension – afferentation of exercise pressor reflex Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University15 Skeletal muscle metabolism Adopted from: D.U.Silverthorn: Human Physiology (An Integrated Approach) Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University16 Reaction of the body to exercise ̶ Sympathetic NS (ergotropic system) ̶ Cardiovascular changes ̶ Respiratory changes ̶ Metabolic changes ̶ HOMEOSTASIS Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University17 Anticipation of exercise ̶ Reaction of the body (cardiovascular system) ̶ Prepares the body for the increased metabolic turnover in the exercising skeletal muscles ̶ Similar to the early response to exercise ̶ Resembling fight-or-flight reaction Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University18 Cardiovascular response to exercise ̶ Increased cardiac output ̶ Redistribution of blood: Vasoconstriction in inactive skeletal muscles, the GIT, skin, (kidneys) Vasodilation in active muscles (metabolic autoregulation) ̶ Increased venous return ̶ Histamine release ̶ Epinephrine release (adrenal medulla) ̶ Thermoregulation Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University19 Increase of cardiac output. Cardiac reserve ̶ CO = SV x HR (SNS: positive inotropic and chronotropic effects) ̶ Cardiac reserve = maximal CO / resting CO (4 – 7) ̶ Coronary reserve = maximal CF / resting CF (~3.5) ̶ Chronotropic reserve = maximal HR / resting HR (3 – 5) ̶ Volume reserve = maximal SV / resting SV (~1.5) CO – cardiac output; CF – coronary flow; SV – stroke volume; HR – heart rate Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University20 Cardiac reserve in healthy and failing heart 0 10 20 30 40 0 1 2 3 4 5 CO[L/min] External power output [W/kg] trained (athlete´s heart) untrained (physiological response) heart failure Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University21 Changes of arterial blood pressure PARAMETER AT REST DURING EXERCISE INCREASE (x) Cardiac output [L/min] 5 – 6 25 (35) 4 – 5 (7) cardiac reserve Heart rate [1/min] (45) 60-90 190 – 200 (220) age-dependent 3 – 5 chronotropic reserve Stroke volume [mL] 75 115 ~1.5 volume reserve Systolic BP [mmHg] 120 static work ↑ dynamic work ↑↑ Diastolic BP [mmHg] 70 static work ↑↑↑ dynamic work ─ / ↓ Mean arterial P (MAP) [mmHg] ~90 static work ↑ dynamic work ─ / ↑ Muscle perfusion [mL/min/100g] 2 – 4 60 – 120 (180) static vs. dynamic work 30 (10% COmax) Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University22 Respiratory response to exercise ̶ Respiratory centre - ↑ ventilation ̶ chemoreceptors: ↑ pCO2 + ↓ pH ̶ proprioceptors in lungs ̶ Sympathetic stimulation (stress – anticipation) Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University23 Respiratory response to exercise PARAMETER AT REST DURING EXERCISE INCREASE (x) Ventilation [L/min] 6 – 12 90 – 120 15 – 20 respiratory reserve Breathing frequency [1/min] 12 – 16 40 – 60 4 – 5 Tidal volume (VT) [mL] 0.5 – 0.75 ~ 2 3 – 4 Pulmonary artery blood flow [mL/min] 5 – 6 25 – 35 4 – 6 O2 uptake (VO2) [mL/min)] 250 – 300 ~ 3000 10 – 12 (25) CO2 production [mL/min] ~ 200 ~ 8000 ~ 40 Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University24 Oxygen uptake by lungs ̶ Spiroergometry ̶ Resting VO2: ~3.6 mL O2 / (min x kg) ̶ VO2 max – objective index for aerobic power ̶ untrained middle age person: 30 – 40 mL O2 / (min x kg) ̶ elite endurance athletes: 80 – 90 mL O2 / (min x kg) ̶ HF / COPD patients: 10 – 20 mL O2 / (min x kg) Adopted from: https://studentconsult.inkling.com/read/boron- medical-physiology-3e/chapter-60/figure-60-6 Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University25 Determinants of VO2 max 1. Uptake of O2 by the lungs ̶ pulmonary ventilation 2. O2 delivery to the muscles ̶ blood flow (pressure gradient – cardiac output x resistance) ̶ hemoglobin concentration 3. Extraction of O2 from blood by muscle ̶ pO2 gradient: blood - mitochondria Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University) 26 Oxygen consumption during exercise ̶ Oxygen debt Adopted from: D.U.Silverthorn: Human Physiology (An Integrated Approach) Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University27 Blood gases during exercise Adopted from: D.U.Silverthorn: Human Physiology (An Integrated Approach) Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University 28 Energy substrates used by skeletal muscle during exercise ̶ Low-intensity e.: fats ̶ High-intensity e.: glucose Adopted from: D.U.Silverthorn: Human Physiology (An Integrated Approach) Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University29 Energy substrate use – aerobic vs. anaerobic Adopted from: D.U.Silverthorn: Human Physiology (An Integrated Approach) Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University30 Testing of fitness ̶ Spiroergometry ̶ Standardised workload ̶ exactly: in W/kg ̶ comparative (simple, inaccurate): in MET ̶ metabolic equivalent (actual MR / resting MR) ̶ 1 MET = uptake of 3.5 ml O2/kg.min ≈ 4.31 kJ/kg.h ̶ sleeping ≈ 0.9 MET; slow walking ≈ 3-4 MET; fast running ≈ 16 MET Marie Nováková, Department of Physiology, Faculty of Medicine, Masaryk University31 Indexes of fitness ̶ W170 [W/kg] ̶ VO2 max [mL O2 / (min x kg)] ̶ Aerobic / anaerobic threshold ̶ Fatigue ̶ Training ̶ Adaptation to exercise