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Energy for movement

Energy for movement. About 60-70% of the energy in human body degraded to heat. The remainder used for mechanical work and cellular activities. Energy derived from food sources – carbohydrates, fats, proteins. Energy stored in a high energy coupmpound – ATP

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Energy for movement

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  1. Energy for movement • About 60-70% of the energy in human body degraded to heat. The remainder used for mechanical work and cellular activities. • Energy derived from food sources – carbohydrates, fats, proteins. • Energy stored in a high energy coupmpound – ATP • Carbohydrates provide about 4 kcal of energy per gram, fat – 9 kcal, carbohydrate energy more accessible. Protein provide also energy.

  2. ATP production • ATP-PCr system • Glycolytic system • Oxidative system ATP-PCr system • Rapid process, does not require O2 – anaerobic • Sprint exercise – depletion of PCr and ATP. • ATP and PCr – energy for 3-15 s.

  3. 5.4 – str 97

  4. Glycolytic system • Breakdown of glucose – glucolysis • Glycolytic enzymes – pyruvic acid  lactic acid • ATP-PCr and glycolytic systems  major sources of energy during early minutes of high intensity exercise • Muscle lactic acid resting value – 1 mmol.kg-1 • Increase to 25 mmol.kg-1 in sprint events  inhibition of glycogen breakdown – impairment of glycolytic enzyme function. A decrease of fibers calcium binding capacity  impedement muscle contraction

  5. Oxidative system • Oxidative production of ATP within mitochondria primary method of energy production during endurance events. • Oxidative production of ATP involves: • Glycolysis • Krebs cycle • Electron transport chain

  6. Glycolysis - Pyruvic acid – oxygen  acetyl coenzyme A (Acetyl CoA) (fig. 20 - see next slide) Krebs cycle (Citric acid cycle)  oxidation of acetyl CoA  2 moles of ATP  CO2, H2. Electron transport chain – H2 nicotinamide adenine nucleotide (NAD), flavin adenine dinucleotide (FAD)  splitting H2 atoms to proton and electrons + O2  H2O + ATP. 1 molecule of glycogen  39 molecules of ATP

  7. Oxidation of fat • Muscle and liver glycogen stores – 1,200 – 2,000 kcal • Fat store in muscle fiber and fat cells  75,000 kcal. • Triglycerides – major energy source • TG  broken to glycerol and free fatty acids  lipolysis (lipases) – blood  muscles  beta oxidation (cleving carbon chains of FFA) • Fat oxidation requires more O2 than carbohydrate oxidation – fat – 5.6 ATP molecules per O2 molecule used – carbohydrate – 6.3 ATP

  8. Protein metabolism • Energy yield – 5.20 kcal per gram • Utilisation less than 5-10% of total energy expended • Amino acids – conversion into glucose – gluconeogenesis. Others – various intermediates of oxidative metabolism (acetyl CoA).

  9. Oxidative capacity of muscle (Qo2) • Mesure of maximal capacity to use oxygen depending on oxidative enzyme levels, fiber-type composition, oxygen availability • Enzymes measured – succinate dehydrogenase (SDH) Citrate synthase (CS) • Endurance athletes muscles – 2-4x greater enzyme activities • ST fibers – greater oxidative capacity – more mitochondria, higher concentration of oxidative enzymes

  10. Measuring energy use during exercise • 40% of the energy liberating during metabolism of glucose and fats used to produce ATP. 60% converted to heat – measuring by direct calorimetry insulated airtight chamber • Not used in practice

  11. Indirect calorimetry – measuring respiratory exchange of O2 and CO2 • Respiratory exchanging ratio – RER = Vco2/Vo2 • RER – 1  the cells are using only glucose • RER – 0.7  -“- fat

  12. Calculations are valid during rest or steady state exercise Isotopic measurement – C13, 2H (deuterium, 2H218O turnover rate

  13. Estimates of anaerobic effort • Post-exercise oxygen consumption Oxygen debt – excessive post-exercise oxygen consumption - EPOC

  14. The lactic threshold The point at which blood lactate begins accumulate above resting values during exercise of increasing intensity. The onset of blood lactate accumulation (OBLA) is a standard value set at either 2.0 or 4.0 mmol lactate.L-1 O2 and is used as a common reference point. Expressed as percentage of Vo2 max – best determinant of athletes pace in endurance events. Untrained people – lactate threshold at 50-60% of Vo2-max, in elite runners at 70-80%, lactate formation contributes to fatigue

  15. Energy expenditure at rest and during exercise • The metabolic rate – L O2 per day x kcal per L O2 = = 432 L O2 x 4.80 kcal L O2 = 2 074 kcal.day • Basal metabolic rate – influenced by body weight, body surface area, age, body temperature, stress, hormones (thyroxin, epinephrine)

  16. Maximal capacity for exercise • Maximal oxygen uptake – VO2-max . aerobic capacity. • Best measurement for cardiorespiratory endurance and aerobic fitness. • Individual needs for energy vary witth body size, Vo2-max expressed in mililitre O2 per kg body weight per minute. • Poorly conditioned adults – 20 ml.kg.min. • Active young male – 38-42 ml • Highest Vo2-max – 94 ml for men, 47 ml for women

  17. Succes in endurance activities depending on: • High Vo2-max, high lactate threshold, high economy of effort, or low Vo2 for the same rate of work, high percentage of ST muscle fibers Energy lost of various activities • Total daily caloric expentiture depends on: Activity level, age, gender, size, weight, body composition.

  18. Causes of fatigue • Fatigue – sensation of tiredness and acompanying decrements in muscular performance Mechanisms • Energy systems – PCr depletion, glycogen depletion • Metabolic by-products • Nervous system • Failure of fiber´s contractile mechanism PCr depletion • Biopsy studies – repeated maximal contraction, fatigue coincides with PCr depletion. • Training experience  optimal pace – most efficient use of ATP and PCr for the entire event.

  19. Glycogen depletion • Muscle glycogen decrease – coincidence of fatigue sensations • Glycogen depletion and hypoglycemia limit performances in activities lasting 30 min or longer Metabolic by products • Lactic acid, increase in H.  pH decrease to 6.9-6.4  inhibition of phosphofructokinase decrease of glycolysis  decrease of ATP, recovery of pH after exhaustive sprint bout requires 30-35 minutes

  20. Neuromuscular fatigue • Nerve impulse transmission at the motor end plate fails in fatigued muscle due to: synthesis of ACH reduced, cholinesterase hyperaction, increase in muscle fiber membrane threshold, decrease or intracellular K. The central nervous system • CNS may slow the exercise pace to tolerable level to protect the athlete • Perceived fatigue precedes physiological F. and athletes can often be psychologically encouraged to continue.

  21. Hormonal regulation of exercise • Hormonal changes during exercise:

  22. Regulation of glucose metabolism during exercise • Plasma glucose levels increase regulated by glucagon, epinephrine, norepinephrine, cortisol. • Glucagon – breakdown of glycogen, glucose formation from aminoacids. • Catecholamines – increase in glycogenolysis • Cortisol – increase in protein catabolism – freeing aminoacids – gluconeogenesis • Glucose uptake by the muscles facilitated by insulin. Exercise enhances insulin binding to receptors on the muscle fiber.

  23. Fat metabolism during exercise • When carbohydrate reserves are low – more fat oxidation for energy used – facilitated by cortisol, catecholamines and growth hormone. • Cortisol – acceleration of lipolysis – activating lipase – reducing triglycerides to FFA and glycerole. • Prolonged exercise – cortisol levels decrease – catecholamines and GH take over cortisol´s role.

  24. Endocrine system – critical role in regulation of ATP production – control the balance between carbohydrate and fat metabolism.

  25. Hormonal effect on fluid and electrolyte balance during exercise. • Fluid balance – critical for optimal cardiovascular and thermoregulatory function. • Exercise – water shift from plasma to intersticial and intracellular spaces – metabolic byproducts accumulation in and around the muscle fibers – increase of osmotic pressure – water drawn there. Sweating increase – combined effect – muscles gain water at the expense of plasma volume – decrease of blood pressure  decrease of blood flow to muscles and skin  impedement of athletic performance.

  26. Endocrine system – regulation of fluid and electrolyte balance by aldosteron and renin-angiotensin mechanism. • Kidney – secretion of enzyme renin converts plasma protein – angiotensinogen into active form angiotensin I – further converted to angiotenzin II  potent arteriole constriction – increase in peripheral reasistance – increase in blood pressure. Angiotensin II trigger aldosteron release from adrenal cortex aldosteron  sodium reabsorption in kidneys  retention of water. • Antidiuretic hormone (ADH) – released when increased solute concentration of blood.

  27. Exercise – shift of water out of blood – blood more concentrated – sweating – increase in plasma concentration -  blood osmolality. Hypothalamus – osmoreceptors triggering ADH release from posterior pituitary - reabsorption of water in kidneys. • Further factors – metabolic water production via oxidation increases water returning from muscles back into blood.

  28. Postexercise hormone activity and fluid balance • Influence of aldosterone and ADH persist for 12-48 hr after exercise – reduced urine production – protection of dedydration - heavy training – expansion of plasma volumes – dilution of various blood constituents – hemodilution (e.g. hemoglobin – anaemic appearance).

  29. Metabolic adaptations to training • Adaptations to aerobic training Adaptations occur in the muscles, energy systems, cardiovascular systems. Adaptation in muscle • Repeated use of muscle fiber – changes in their structure aand function. Aerobic training stressed ST muscle fibers more than FT fibers  enlargement 7-22%. • Increase in number of capillaries per muscle fiber improvement blood perfusion in the muscles

  30. Adaptation in muscle – contin. • Increase in muscle myoglobin content by about 75-80% - more stores of oxygen. • Increase the number and size of mitochondria muscle provided with much more efficient oxidative metabolism. • Activities of many oxidative enzymes increase (succinate dehydrogenase, citrate syntase) - all these changes in muscles combined with adaptations in oxygen transport system  enhanced functioning of oxidative system  improvement of endurance.

  31. Adaptation of energy sources • Trained muscle stores more glycogen and more fat (triglyceride). • Activities of enzymes involved in beta oxidation of fat increase  increase in free fatty acid levels  increased use of fat as energy source, sparing glycogen

  32. Training the aerobic system • Volume of training – optimum – equivalent to an energy expenditure 5-6,000 kcal.week  approximately 80-95 km of running per week – individual differences. • Intensity – high intensity, intermittent bouts of exercise – more improvement than long, slow, low-intensity training bouts. • Interval aerobic training – repeated bouts of high intensity performance separated by brief rest periods(10-15 s). • Continuous training – one prolonged bout of exercise – boring for athletes

  33. Adaptations to anaerobic training • Muscular activities requiring near maximal force production (sprint, weight lifting)  energy needs met by the ATP-PCr system and by anaerobic breakdown of muscle glykogen • Anaerobic training – increases the ATP-PCr and glycolytic enzymes, no effect on oxidative enzymes

  34. Other adaptations to anaerobic training • In addition to strength gains – improvement of efficacy of movement (economyzing use of muscle´s energy supply), aerobic energetics (often small), buffering capacity (better tolerance of acids, accumulating during anaerobic glycolysisi) – buffers (bicarbonates, phosphates) combine with H· - delay of muscle fatigue

  35. Monitoring training changes • Mesuring of Vo2-max – impractical, not measure of muscle adaptation to training • Muscle measurement of blood lactate levels during exercise bouts of incresing intensity – impractical • Single blood lactate value after a fixed pace activity. Measurement at various times during a training period.

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