Nutrition 2420 Chapter 12

What is the main goal of fueling physical activity?

To convert carbohydrates, proteins, and fats into energy (ATP)

What is ATP?

The body's usable form of energy

Where in the cell is energy (ATP) primarily produced?

Mitochondria

What do energy systems do during physical activity?

Work together as a continuum to fuel the body depending on exercise duration

How long does ready-made ATP supply energy?

~2-3 seconds

What type of activity relies on ready-made ATP?

Very short, immediate bursts of activity

What is the next energy system after ATP is depleted?

Creatine phosphate system

How long does creatine phosphate provide energy?

~15 seconds

What are sources of creatine?

Diet (meat)

Supplementation

Biosynthesis in the body

What does creatine phosphate do?

Helps regenerate ATP quickly

What are the three macronutrients used for energy?

Carbohydrates

Fats

Proteins

How are carbohydrates stored for energy?

As glycogen → broken into glucose

How are fats stored for energy?

As adipose tissue → broken into fatty acids

How are proteins used for energy?

Broken into amino acids

What provides instant energy during exercise?

Stored ATP and creatine phosphate

What provides short-term energy (15 sec-2-3 min)?

Anaerobic metabolism of glucose

What provides long-term energy (2-3 min and beyond)?

Aerobic metabolism (glucose + fatty acids + some protein)

What determines which fuel source is used during exercise?

Exercise intensity

What fuel is primarily used at rest?

Fatty acids (majority)

What fuel increases as exercise intensity increases?

Carbohydrates (glucose)

When is protein used for energy?

In small amounts, across activity levels

Which type of activity uses the greatest proportion of carbohydrates?

High-intensity, shorter duration exercise

Which uses more fat as fuel?

Lower-intensity, longer-duration exercise

What are the four major energy sources during exercise?

Muscle glycogen

Liver glycogen

Muscle triglycerides

Adipose tissue

How does increasing exercise intensity affect fuel use?

↑ Carbohydrate use

↓ Fat use

What is the "fat-burning zone"?

Lower intensity exercise where a higher percentage of energy comes from fat

Does the fat-burning zone burn more total calories than higher intensity exercise?

No—higher intensity burns more total calories overall

What is the main fuel for moderate to high-intensity exercise (60-85% VO₂ max)?

Glycogen

Where is glycogen stored in the body?

Liver: ~80-100 g

Muscle: ~300-400 g

What happens when glycogen stores are depleted?

Cannot maintain exercise intensity

Cannot maintain work output

How much carbohydrate should athletes consume daily?

5-12 g/kg/day

Example: How much CHO does a 70 kg athlete need?

350-840 g/day

What is carbohydrate loading?

Increasing carb intake while decreasing training to maximize glycogen stores

When is carb loading typically done?

~1 week before an event

Who benefits most from carbohydrate loading?

Endurance athletes (marathoners, triathletes, etc.)

Does carb loading always improve performance?

No

What is a possible downside of carb loading?

Can cause adverse side effects

What is the main focus of carbohydrate intake for athletes?

Maintaining glycogen stores

How much CHO should endurance athletes consume daily?

8-12 g/kg/day

How does exercise duration affect carb needs?

Longer duration → more carbohydrate needed

How much CHO should be consumed before exercise (>90 min)?

1-4 g/kg several hours before

What may improve endurance performance when added pre-exercise?

Protein

How much CHO should be consumed during exercise (>60 min)?

30-60 g/hour

What type of drink is recommended during endurance exercise?

6-8% carbohydrate-electrolyte solution

Example of intake during exercise?

6-12 oz Gatorade every 15 minutes

Why consider GI tolerance during exercise?

To avoid stomach discomfort

How soon should carbs be consumed after exercise for rapid recovery?

Within 30 minutes

How much CHO should be consumed post-exercise for recovery?

0.6-1.2 g/kg

How often should carbs be consumed after exercise for optimal recovery?

Every 2 hours for 4-6 hours

What are benefits of adding protein after exercise?

Faster glycogen recovery

Reduced muscle damage

When is post-exercise timing less critical?

When rapid glycogen recovery is not needed

What type of carbs are recommended for athletes?

Fiber-rich, less processed foods

Simple carbs for quick glycogen restoration

How does resistance training affect glycogen levels?

Decreases glycogen, but less than endurance exercise

Does carb intake before/during resistance training improve performance?

Not likely, but may reduce glycogen loss

What are carbohydrate adaptations with training?

↑ Glycogen storage in muscle

↑ Mitochondrial mass

What does increased mitochondrial mass mean?

More mitochondria in muscle

Why are carb adaptations beneficial?

Improve energy production and endurance

What percentage of calories should come from fat?

20-35%

How much saturated fat is recommended?

<10% of calories

Is fat timing important for exercise?

No specific timing needed

What do fat-containing foods provide?

Energy

Fat-soluble vitamins

Essential fatty acids

What happens if fat intake is too low?

Can negatively affect training and performance

What fat-related adaptations occur with training?

↑ Fat use for energy

↑ Fat storage in muscle

↑ Mitochondrial mass

↑ Enzymes for fat metabolism

↑ Ability to use fat from blood

Why are fat adaptations beneficial?

They spare carbohydrates

How much protein do active individuals need?

1.0-1.8 g/kg/day

How much protein might highly active athletes need?

Up to 1.8-2.0 g/kg/day

Is protein timing as important as total intake?

No—total intake matters more

How much protein supports muscle protein synthesis (MPS) throughout the day?

20-40 g every 3-4 hours

What is the ideal timing for protein after resistance exercise?

Immediately or within 2-3 hours

How much protein maximizes MPS after exercise?

20-40 g (with 10-12 g essential amino acids)

How long are muscles sensitive to protein after training?

At least 24 hours

What protein intake is recommended before sleep?

30-40 g casein protein

Why consume protein before sleep?

Increases overnight muscle protein synthesis

What type of protein is recommended?

High-quality protein

Why are fluids important during physical activity?

Enable cooling (sweating)

Prevent dehydration

Prevent heat-related illness

When should fluids be consumed?

Before, during, and after exercise

What is a good indicator of proper hydration?

Maintaining body weight

Why is hydration especially important in hot environments?

Higher risk of dehydration

What does sodium in sports drinks do?

Stimulates thirst

Promotes water retention

What should a sports drink contain?

5-10% carbohydrates

0.5-0.7 g sodium/L

Water + electrolytes

How much fluid should be consumed 4 hours before exercise?

0.17-0.24 oz/kg

How much fluid should be consumed 2 hours before exercise?

0.10-0.17 oz/kg

What should be consumed during exercise <1 hour?

Water

What should be consumed during exercise >1 hour?

Sports drink

How much fluid should be consumed after exercise?

~3 cups per pound lost

Do athletes need more vitamins and minerals?

Some needs may be slightly elevated

Can micronutrient needs be met with diet alone?

Yes, with a balanced diet (no supplements usually needed)

Which B vitamins may be needed in higher amounts?

B1

B2

B6

How should calcium intake be handled in athletes?

Meet existing RDA

Who should be careful about calcium intake?

Lactose intolerant individuals

Vegans

Why are athletes at risk for low iron?

Loss through sweat, urine, feces

RBC breakdown (especially runners)

Should iron supplements be taken automatically?

No—only after testing iron status