Transcript Lecture 11
2:45-3:15 PM on the Thursday (28th November). Meet with quality assurance external reviewers for the school of professional studies. Nutrition student volunteers please email me and Marcy MacKinnon: [email protected] indicating whether you are year 1 or 2 and with you willingness to do so- your help is very much required and essential. Thank you!!! Lecture 11- 21 November 2013 This lecture is based largely on CHAPTER 23 IN KRAUSE'S FOOD NUTRITION AND DIET THERAPY (ON RESERVE IN LIBRARY) AND CHAPTERS 7,8,9 IN ROLFES ET AL. Final exam-120 multiple choice-120 marks from vitamins to end of course -4 short answer questions-15 points each for a total of 60 points covers whole course -3 hours- 180 marks Lecture 11 Outline Metabolic aspects of Nutrition and fitness/Sports Nutrition Energy production ATP Anaerobic pathway Aerobic pathway Energy continuum Sources of fuel Outline of lecture 11 Energy production Substrate choice Intensity Duration Effect of training Diet Outline of lecture 11 Nutritional Requirements Fluid Fluid Balance Fluid Absorption Factors affecting fluid absorption Requirements Short duration Endurance Outline of lecture 11 Nutritional Requirements Carbohydrate Types of carbohydrate Pre-event During event Post-event Outline of lecture 11 Nutritional Requirements Protein Endurance Resistance Exercise Amino acid supplementation Outline of lecture 11 Nutritional Requirements Lipid Minerals Iron Calcium Vitamins Anti-oxidant vitamins and Bcarotene C E B vitamins Outline of lecture 11 Regulation of metabolism More Detailed Comments Energy production Aerobic and anaerobic both provide ATP but which system predominates depends on oxygen supply to the tissues Energy production ATP Energy currency of the cell ATP to ADP plus Pi -done by ATPase Creatine phosphate is split to creatine and phosphate -this provides the energy to resynthesise ATP via creatine kinase Energy production ATP limited amount of creatine phosphate in the body so this is a very limited way to replace ATP- creatine phosphate process is anaerobic if all-out exercise -this process can only go on for 5-8 seconds- eg power lifting Energy production Anaerobic pathway No oxygen Glycolysis is the quickest way to make ATP Lactic acid is endproduct (enzyme implications) Two hydrogens transferred to pyruvate thus making lactate- This results in the freeing of NAD to participate further in making ATP-but relatively small amount of ATP synthesis Energy production Anaerobic pathway Lactic acid is rapidly removed from the muscle and transported in the blood and is eventually converted to energy in the muscle, liver or brain OR it is converted to glycogen Conversion to glycogen occurs largely in the liver and to some extent in the muscle Lactic acid buildup in the blood leads to drop in pH resulting in enzymatic activity drops which in turn results in fatigue Energy production Anaerobic pathway Oxygen debt-recovery oxygen consumptionthe difference between oxygen consumption in the post-exercise recovery phase and the oxygen consumption at rest Fuel source is limited to glucose and produces a relatively small amount of ATP relative to aerobic metabolism All out effort for 60-120 seconds Energy production Aerobic pathway If going for continued muscle activity of more than 90-120 seconds one needs oxygen Energy is stored in high-energy phosphate bonds in ATP through a complex series of enzymatically guided reactions involving separation of hydrogen atoms from the parent compounds Energy production Aerobic pathway Vital to this process is the presence of coenzymes which act as hydrogen acceptors until the process of oxidative phosphorylation results in the formation of ATP Ultimately hydrogen combines with O2 to form water and the coenzymes are freed to accept more hydrogen so as to continue the process Energy production Aerobic pathway Glucose is broken down much more efficiently than is the case with anaerobic glycolysis In the presence of oxygen, pyruvate is converted to Acetyl CoA Acetyl CoA enters the mitochondria and is then introduced into the Kreb’s cycle Energy production Aerobic pathway Proteins and lipids can also be metabolized to produce ATP Lipids- the beta oxidation of lipids produces a large amount of ATP Proteins can be catabolised to Acetyl CoA or to Kreb’s cycle intermediates and in this way produce ATP Break Energy production Energy continuum All pathways can produce ATP At the beginning of any exercise whatsoever anaerobic metabolism is in place to produce ATP If the person continues to exercise at a moderate level for a prolonged period then the aerobic pathway will become the predominant pathway for energy production (eg marathon run) Energy production Energy continuum If the person continues to exercise for a short period of high power and high intensity then the anaerobic pathway will become the predominant pathway for ATP energy production(eg 100 metre sprint) Production of ATP is therefore a continuum that depends on the: -availability of oxygen -the capacity for intensity of the exercise -the capacity for the duration of the exercise Energy production Energy continuum There is an inverse relation between the capacity for intensity and the capacity for the duration of the exercise -one cannot perform high intensity exercise over a long period of time -the duration increases as the intensity drops and as the intensity of the exercise increases the duration of that exercise drops Energy production Energy continuum -the aerobic pathway cannot tolerate the same level of intensity as the duration increases due to the decreased availability of oxygen and the production of lactic acid Energy production Energy continuum -as the intensity increases the power output decreases POWER = WORK/TIME WORK = FORCE X DISTANCE -as the intensity decreases the power output increases POWER = WORK/TIME WORK = FORCE X DISTANCE Energy production Sources of fuel as the duration increases more energy is obtained from fat (fatty acids) and as the duration decreases and the intensity increases more energy is obtained from carbohydrate carbohydrate is obtained from dietary carbohydrate, glycogen or amino acids (amino acids can be synthesized to glucose-this process is known as gluconeogenesis) Energy production Sources of fuel Kreb’s cycle-alanine is the main amino acid contributing to the Krebs cycle -3 carbon units of glucose contributing to the Krebs cycle -2 unit carbons of fatty acids contributing to the Kreb’s cycle Energy production Sources of fuel Kreb’s cycle -all of these substrates are used most of the time however the intensity and duration of the exercise dictates the relative rates of substrate utilisation Energy production Substrate choice Intensity- high intensity must rely on carbohydrate Because oxygen is not available for high intensity exercise glycogen must be utilized Glycogen catabolism is much higher than with aerobic activity18-19 times faster (2 ATP versus 36-38 ATP) -Energy production Substrate choice Intensity-Hockey, basketball for eg favour higher glycogen utilization rates than marathon running while moderate intensity exercise favours 50/50 split of (glycogen)/(glucoselipid) use -Energy production Substrate choice Low intensity exercise like walking is entirely aerobic and most of the ATP comes from lipid Fat yields 4.65 kcal / L of oxygen consumed vs for carbohydrate a yield of 5.01 kcal/L of oxygen consumed -thus in longer term exercise carbohydrate use is favoured Once the glycogen stores are depleted then that is the end of the high intensity exercise Energy production Substrate choice Duration-the longer the event the greater the proportion of lipid used to produce ATP -consequently the lower the amount of lactate produced Effect of training-increase number of mitochondria and activity of ATP producing enzymes Energy production Substrate choice Diet-dictated by fuel utilization for a particular event -high intensity requires more carbohydrate in the diet -lower intensity requires more lipid in the diet however do not consume a high fat dietcrowd out carbs and run the risk of heart disease Class exercise Explain the effects of exercise intensity, duration and training on substrate utilisation. Break Nutritional Requirements Fluid Fluid Balance Important for maintaining blood flow which in turn is important for supplying blood to skin and hence temperature control 75 percent of energy goes out as heat-therefore must sweat regulated by kidney, sweat loss, feces, respiration and fluid intake important to consume sodium and water to replace water lost as sweat-thus blood sodium is maintained and therefore so are hormone levels which limit the rate of urine production Nutritional Requirements Fluid Absorption Factors affecting fluid absorption -glucose and sodium travel across intestine on same carrier Nutritional Requirements Fluid Requirements Short duration -if several heats before actual race this can be problem for hydration - plain water dilutes the blood, increases urination and results in dehydration Endurance -plain water lowers blood glucose concentrations thus increasing the demand on muscle glycogen Nutritional Requirements Carbohydrate Types of carbohydrate After glycogen runs out must use gluconeogenesis to maintain blood glucose levels Glycogen loading is important-eg pasta diet some have suggested complex carbs are better at glycogen loading in muscle than are simple carbs but this is debatable Nutritional Requirements Carbohydrate Pre-event Takes care of hunger Maintains adequate blood glucose levels for event During event Maintains blood glucose and delays fatigue Post-event Builds glycogen up in muscle after depletion Nutritional Requirements Protein Endurance Less required than for resistance events Resistance Exercise More required than for endurance events -muscle mass issue Nutritional Requirements Protein Amino acid supplementation A waste of time- eat more calories in accordance with Canada’s food guide to meet increased energy demands and this will easily meet added protein/amino acid requirements Can lead to dehydration, loss of urinary calcium, weight gain and stress on the kidney and liver Nutritional Requirements Lipid -supplies essential fatty acids -important energy source during endurance exercise -less important as an energy source for high intensity exercise Class exercise How do the 6 nutrient classes work together to allow: a) Aerobic exercise b) Anaerobic exercise Break Nutritional Requirements Minerals Iron -oxygen carrying-hemoglobin and myoglobin -part of electron transport chain-ATP Calcium -bone mass Nutritional Requirements Vitamins Anti-oxidant vitamins and b-carotene, vitamin C and E -exercise produces increased amount of lipid peroxides and free radicals-damage muscle -supplements are not required-no evidence that they improve performance B vitamins -important co-enzymes in energy production -B12-supplement required in strict vegans Regulation of Metabolism Oxygen supply As intensity of exercise increases the oxygen supply becomes limiting-with training one can supply more oxygen Substrate supply Availability of co-enzymes Hydration Mechanisms described for each of the nutrient classes Class exercise What is the major direction of metabolism during exercise? after exercise? Why ?