Nu fsp chapter 4

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Chapter 4Lecture Slides

Dietary Carbohydrates

• One of the most important nutrients in your diet, from the standpoint of both health and athletic performance, is dietary carbohydrate.

What are the different types of dietary carbohydrate?

• Carbohydrates– Carbon, hydrogen and oxygen

• Simple carbohydrates– Monosaccharides

• Name them

– Disaccharides• Name them and the monosaccharides for each

What are some common foods high in carbohydrate content?

How much carbohydrate do we need in the diet?

• Recommended Dietary Allowance (RDA)– 130 grams

• Acceptable Macronutrient Distribution Range (AMDR)– 45-65% of energy intake

• Daily Value (DV)– 60% of daily energy needs– 300 grams on a 2,000 Calorie diet– 25 grams of fiber

Recommended carbohydrate in the diet

• Sport nutritionists– Recommend high end of AMDR– 60-70% or higher– Diet containing 3,000 Calories

• 450 grams of carbohydrate at 60% level

Figure 4.4

What happens to the carbohydrate after it is absorbed into the body?

• Most dietary carbohydrates eventually are converted to glucose which circulates in the blood

• Carbohydrate foods have different effects on blood glucose levels

• The glycemic index and glycemic load

Fates of blood glucose

• May be used for energy• May be converted to liver or muscle glycogen• May be converted to and stored as fat in adipose

tissues• May be excreted in the urine if in excess

Figure 4.6

Carbohydrate storage in the body

Carbohydrates for Exercise

• Carbohydrate as an energy source during exercise• Effect of training on carbohydrate metabolism• Methods of providing carbohydrate

– Before competition– During competition– After competition– During training

In what type of activities does the body rely heavily on carbohydrate as an energy source?

• Carbohydrate contributes about 40% of energy needs at rest

• Fat is main energy source during low exercise intensity, such as 40-50% VO2max

• Carbohydrate is major source during – Very high intensity anaerobic exercise– High intensity (>65% VO2max) aerobic exercise– Prolonged aerobic exercise events– Intermittent high-intensity exercise sports

Carbohydrate sources for exercise

• Muscle glycogen is a very important source• Liver glycogen is converted to blood glucose• Blood glucose is delivered to muscles

Hypoglycemia

• The human body attempts to prevent hypoglycemia• Hormone activity

– Insulin – Glucagon

Hormones and glucose metabolismHormone Gland Stimulus Action

Insulin Pancreas Increase in blood glucose

Helps transport glucose into cells; decreases blood glucose levels

Glucagon Pancreas Decrease in blood glucose; exercise stress

Promotes gluconeogenesis in liver; helps increase blood glucose levels

Epinephrine Adrenal Exercise stress; decrease in blood glucose

Promotes glycogen breakdown and glucose release from the liver

Cortisol Adrenal Exercise stress; decrease in blood glucose

Promotes breakdown of protein; stimulates gluconeogenesis

How is low muscle glycogen related to the development of fatigue?

• Low muscle glycogen and aerobic exercise– Muscle glycogen is the primary fuel for endurance

athletes, such as marathon runner

• Studies have shown physical exhaustion to be associated with very low muscle glycogen levels. However, other studies have shown fatigue with some muscle glycogen remaining.

Optimal supplementation protocol

• Consume carbohydrates both before and during the exercise task.

When, how much, and in what form should carbohydrates be consumed before or during exercise?

• Athletes who may benefit from carbohydrate intake– Endurance exercise– Intermediate high-intensity exercise

• Fluid replacement is also an important consideration

What is the importance of carbohydrate replenishment after prolonged exercise?

• Rapid restoration of muscle glycogen important for some athletes– Repeated bouts of prolonged, intense exercise on the

same day– Prolonged, intense exercise on consecutive days

Carbohydrate-rich diets for athletes

• Sport nutritionists recommend that athletes consume about 8-10 grams of carbohydrate per kilogram body weight daily

• For a 70-kg athlete, this would amount to 560 to 700 grams of carbohydrate daily, or the equivalent of 2,240 to 2,800 Calories

• On a 3,500-Calorie daily intake, the carbohydrate would provide 65-80% of daily energy intake.

• This amount of daily carbohydrate would help restore muscle glycogen levels

Carbohydrates during training

• There is no evidence that low-carbohydrate diets improve exercise performance

• A diet rich in healthy carbohydrates may help guarantee optimal energy sources for daily training

• Train high and compete high is the concept of training and competing with high carbohydrate intake.

Carbohydrate loadingWhat is carbohydrate, or glycogen, loading?

• Method of increasing muscle glycogen levels– Also known as muscle glycogen supercompensation

What type of athlete would benefit from carbohydrate loading?

• Athletes who sustain high levels of continuous energy expenditure for prolonged periods– Long-distance runners– Cross-country skiers– Endurance triathletes– Tournament play in intermittent high-intensity exercise

sports

How do you carbohydrate load?

• Athlete should be fully trained• Classic procedure not necessary:

– Depletion stage– Low carbohydrate diet– Carbohydrate loading

• Have about 3-4 days of high carbohydrate intake, about 8-10 grams/kg body weight, or more

• Low and high glycemic index carbohydrates are equally effective• Taper exercise training over the course of a week or longer

Carbohydrate loading procedures

Will carbohydrate loading increase muscle glycogen concentration?

• Most studies report increased muscle glycogen levels following carbohydrate loading procedures

• Both males and females will increase glycogen levels if adequate energy and carbohydrate are consumed

• Muscle glycogen levels may increase two to three times above normal

• Experiment with the protocol during training

Will carbohydrate loading improve exercise performance?

• In general, the procedure is not needed for exercise tasks of short duration

• In general, research supports the use of carbohydrate loading as a means to enhance performance in prolonged endurance exercise tasks– Helps maintain an optimal pace longer– Extra body water may help during exercise in the heat

• Most appropriate protocol is to use both carbohydrate loading and consumption of carbohydrate during the event

Carbohydrates: Ergogenic Aspects

• Metabolic by-products– Pyruvate– DHAP (Pyruvate and dihydroxyacetone)– Lactate salts– Ribose– Multiple carbohydrate products

Soluble and insoluble fiber

• The issue of soluble and insoluble fiber– Difficult to generalize on different health effects of

soluble and insoluble fiber; health effects are due to total fiber, but it may be illustrative to discuss soluble and insoluble fiber effects on health.