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CHO Use Before, During & After Exercise Recall: Important Aspects of Glycogen Use • 1.) Glycogen + Phosphate begins reactions in glycolysis cascade of – in working muscle, free P levels are higher than in non working muscle due to breakdown of ATP and CP 2.) Blood Glucose enters cell via diffusion, then is phosphorylated by hexokinase to G-6-P (takes ATP) blood glucose use 2ATP/mole glucose muscle glycogen use 3 ATP/mole glucose Important Aspects of Glycogen Use (cont.) 2.) continued– , best to use muscle glycogen during exercise because you get more ATP How does the body know to do this? Glucose concentration gradient GLUT 4 transporters 3.) The more glycogen present in muscle, more is used. Why is this? More glycogen more branching more ends exposed to phosphorylase Important Aspects of Glycogen Use (cont.) 4.) When exercising in hot conditions, more epi/norepi is released – more glycogen use (due to glycolysis) – run out of fuel faster appear less trained 5.) Trained individuals have about 50% more stored muscle glycogen than untrained GLUT 4 in muscle glucose uptake from blood glycogen synthase in muscle w/ training CHO use before, during and after exercise 1. Before exercise – 3 days • eat more, store more • humans (trained) can glycogen storage by 50% (takes about three days) • During three days prior to event, eat 70% CHO, only do activity under 50% VO2 max 3 hours focus shifts to liver glycogen effect of glycemic index CHO use before, during and after exercise (cont.) • During exercise for events > 90 minutes, want to consume CHO at rate of 1g/min will slow use of glycogen After exercise must consume >100g CHO w/in 2 hrs post exercise to completely recover Large amount of GLUT 4s activated post exercise very easy to bring glucose into muscle to restore glycogen Hydration during exercise • dehydration causes heart rate – lower cardiac output causes core temp. Sweat rate normal 1 L/hr athletes 2 L/hr Most athletes only consume 500 ml/hr Gastric emptying max rate 2 L/hr controlled by: volume in stomach, and osmolarity in stomach Hydration during exercise (cont.) • Intestinal absorption – max rate 2 L/hr *Unfortunately, people don’t drink 2 L/hr! Three important ingredients in fluid replacement drinks: H2O CHO Na main extracellular ion which enhances H2O retention in small intestine