PET3361 EXAM II STUDY GUIDE 1 Define postabsorptive and postprandial states and explain how each of the macronutrients is absorbed into the system Postabsorptive state Fasting state o After an overnight fast blood glucose is maintained by glycogenolysis break down of glycogen and gluconeogenesis formation of glucose from non carbohydrate source in the liver o Glycogenolysis provides 65 75 of the glucose released o Gluconeogenesis provides the remaining 25 35 of the glucose released by the liver o Muscle glycogen cannot be converted to blood glucose Postprandial sate Fed state o Absorbed glucose is being stored as glycogen glycogenesis in skeletal muscles and liver o Most cells of the body are removing glucose for energy glycolysis especially neurons and red blood cells o Adipose cells remove glucose to form glycerol needed for triglycerides formation and fatty acids Absorption of Carbohydrates o Monosaccharides are absorbed through the wall of the small intestine into capillaries leading to the portal vein o Glucose and Galactose are absorbed by secondary active transport coupled to Na transport into the epithelial cells and then move into the blood by facilitated diffusion o Fructose is absorbed through epithelial cells and into the blood by facilitated diffusion Fats and water are absorbed through Passive absorption Fructose is absorbed through Facilitated absorption Amino Acids and Glucose are absorbed through Active absorption 2 Which hormones control blood glucose and how How does exercise influence these responses o Insulin o Secreted from Beta cells in the Pancreas o Released when blood glucose high o Causes active transport of amino acids into tissue cells o Causes facilitated diffusion of glucose into tissue cells o Leads to a decrease in Blood glucose and increase in stored o Gradually decreases as exercise intensity increases blunted glycogen response o Glucagon o Secreted from Alpha cells in the Pancreas o Released when blood glucose is low o Stimulates glycogenolysis and gluconeogenisis o Stimulates fat breakdown o Causes increased Blood glucose level o Epinephrine Norepinephrine o Work in conjunction with Glucagon to raise blood glucose o Stimulate fat breakdown o Stimulate glycogenolysis and gluconeogenesis o Exercise causes increase in Epinephrine and Norepinephrine levels levels 3 What factors influence CHO use during exercise and how Exercise Intensity o The greater the intensity of exercise the quicker the depletion of stored glycogen o As you increase exercise intensity you increase reliance on CHO and decrease your reliance on fat o The longer the exercise goes the more depleted glycogen stores Exercise Duration get Initial Glycogen Levels o A higher carbohydrate intake causes higher levels of glycogen stores during exercise o Higher levels will last longer will not be depleted as quickly as if the initial glycogen levels were low Training Status o The more trained you are the more efficiently you can use fuels 4 What is the recommended timing for the feeding of CHO before exercise Timing o 30 60 minutes before exercise Some studies with heavy exercise reported reductions in Studies using moderate intensity reported no significant endurance difference Probably better for moderate intensity activity o 3 or more hours before exercise This has been found to improve performance 5 What are the general guidelines for a pre competition meal Pre competition meal general guidelines o Carbohydrate feeding 3 4 hours before exercise o 150 300 grams of carbohydrates 3 5 grams kilogram body weight o Solid or liquid o Relatively little fat or fiber avoid fried foods These cause discomfort digestive rate slows potentially doesn t allow access to other fuels o Limit protein controversy 6 When is it most beneficial to feed CHO during exercise What are the guidelines Feeding glucose or glucose polymers during exercise improves endurance only if the exercise lasts more than 60 minutes o Feeding during exercise spares muscle glycogen type I and maintains your blood glucose level o A glucose electrolyte drink between 4 8 is optimal Feeding glucose during performance DOES NOT help when o Subjects are hyperthermic o During high intensity exercise when fatigue is due to accumulation of H in muscles lasting 20 30 minutes o During events lasting 30 45 minutes 7 How does CHO feeding during recovery influence muscle glycogen Immediate feeding post exercise causes greater glycogen synthesis for the first 2 hours Early feeding post exercise has an increased muscle glycogen storage compared to later feeding post exercise for up to 4 hours 8 What factors enhance glycogen synthesis and how o When depleted this increases the percentage of activated GS I form the more active form of glycogen synthase o Insulin enhances glycogen synthesis and uptake of glucose from Glycogen depletion Presence of Insulin the blood Exercise o Exercise can activate GS I form of glycogen synthase and causes Glut 4 to be present at the cell membrane transporter 9 Know the recovery feeding guidelines for enhancing muscle glycogen storage Guidelines for Post exercise carbohydrates o Feed approximately 1 1 5g kg each hour for the first 4 hours after exercise o Within the first 6 hours after exercise high GI foods or simple CHO provide the best glycogen replacement o These foods increase insulin levels in the blood stimulating glucose transport into the cell and glycogen synthesis o Provide CHO replacement beverage with 70 90 g CHO immediately after exercise if the athlete are eating self selected diets are unable to eat within 2 hours or are not hungry Carbohydrates after exercise o High glycemic carbohydrate rich foods o Either a single large meal or small frequent meals will replenish o SHOULD BE CONSUMED AS SOON AS POSSIBLE glycogen stores AFTER EXERCISE o Avoid fructose and other slow digesting carbohydrates 10 How does muscle damage influence glycogen resynthesis Eccentric exercise causing muscle soreness and damage is accompanied by reduced muscle glycogen resynthesis o This may be due to the damage to the sarcolemma and interference with glucose transport into the muscle fiber o May also be due to the inflammatory response and increased glucose oxidation by neutrophils 11 What are the guidelines for daily CHO intake Daily CHO intake o Feed 5 7 g kg body weight over 24 hour period for moderate duration low intensity training o For moderate or heavy endurance training or competition your recovery diet should