When is glucagon released?
in response to a lowering of blood glucose levels
When is insulin released?
in response to an elevation of blood glucose levels
What are the 3 principles of fuel utilization?
- maintaining glucose homeostasis
- using the fuel that is most efficient
- preserving muscle glycogen core
Most preferred fuel during high intensity exercise? And why?
Carb
because it can metabolize more rapidly than fat to provide ATP to working muscle
Anaerobic
Lactic acid clearance limits duration over which system can be used
Most preferred fuel during moderate intensity and prolonged exercise? And why?
Fat
it’s metabolism provides more ATP than carb
Aerobic
availability of carb limits the body’s ability to generate ATP from fat
Hypoglycemia
abnormally low levels of glucose in the blood
hypoglycemia triggers the release of counter regulatory hormones to prevent further declines in bg levels and promote gluconeogenesis
Insulin
- released from the pancreas and in response to increase blood glucose
- helps transport glucose into cells and decreases blood glucose levels
Glucagon
- released from the pancreas and in response to decrease in blood glucose and exercise stress
- promotes gluconeogenesis in liver and helps increase bg levels
Epinephrine
- released from adrenal and in response to exercise stress and decrease in blood glucose
- promotes glycogen breakdown and glucose release from the liver helps increase bg levels
Cortisol
- released fro the adrenal and in response to exercise stress and decrease in blood glucose
- promotes breakdown of protein and gluconeogenesis and helps increase bg levels
How to prevent hypoglycemia in athletes
- encourage adequate carb intake on a daily basis
- carb rick pre-training, pre-even or snack before activity
- carb feeding during prolonged activity
- carb rich feeding after activity to replenish glycogen stores
Glycemic Index
classifies food based on their impact on bg levels
reflects the rate of digestion and absorption of carb
GI equation
blood glucose area after test food/blood glucose area after reference food x100
Glycemic load
the glycemic index relative to the serving size
GL equation
GL= (GIx CHO/serving)/100
What should be eaten before exercise?
a low GL carb should be eaten before prolonged exercise to promote sustained carb availability and reduce risk of rebound hypoglycemia
What should be eaten during exercise?
moderate to high GL foods to promote rapid intake of carb uptake to blood and decreased reliance on gluconeogensis
What should be eaten after exercise?
high GL carb to support replen of glycogen stores
Rebound Hypoglycemia
insulin release stimulated by excessive glucose before exercise promotes skeletal muscle glucose uptake
exercise also stimulates glucose uptake
there’s so much uptake that hypoglycemia occurs
2 types of sweeteners?
nutritive
non-nutritive
Nutritive sweeteners
- provide calories and influence bg
- white/brown sugar, honey, maple and corn sugar
- sweet tasting because of glucose, fructose, or sucrose (glucose+fructose)
Non-nutritive sweeteners
- don’t provide calories or influence bg
- sweetness comes from other forms
Saccharin
- aka Sweet’N Low
- oldest sweetener (1879)
- 300x sweeter than sucrose
- controversy because of it’s alleged relationship with cancer
Sucralose
- aka Splenda
- 1976
- 400-800x sweeter than sucrose
- not recognized as a carb in the body
- can be used in cooking
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Lecture 118
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Lecture 214
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Lecture 327
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Lecture 432
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Lecture 4 Part 213
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Lecture 522
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Lecture 628
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Nutritional Ergogenic Aids26
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Assessment of Body Size and Composition29
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Nutrition for Body Builders13
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Management of Diabetes and Exercise18
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Disordered Eating and The Female Athlete Triad29
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Sport Nutrition for Child and Adolescent Athletes4
