1. Fundamentals of Exercise for Nutrition Module 4.5

2. Fuel Utilization During Exercise
The chemical reactions that use these substances to make energy are called metabolism.
Two interrelated energy-producing systems:
Aerobic: requiring oxygen.
Anaerobic: not requiring oxygen
Inefficient; generates lactic acid that can be converted into an energy substrate.
The energy used by cells is called ATP. ATP production is synthesized primarily from carbohydrate and fat
As the intensity of the exercise increases, the percent of carbohydrates used to produce ATP increases
Nutrition supplies the fuel (carbohydrate, fat and protein) and the essential structural components of enzymes (cofactors) needed to drive chemical reactions to generate ATP through 3 predominant energy pathways:
Glycolysis
The citric acid cycle (Kreb Cycle)
The electron transport chain.

3. ATP energy production through glycolysis, the citric acid cycle, and the electron transport chain

4. ATP energy production through glycolysis, the citric acid cycle, and the electron transport chain

5. Carbohydrates
Carbohydrate as fuel supports high intensity exercise
Carbohydrate intake can occur prior, during and after exercise
Carbohydrate are limited in the body
Blood Glucose - Constantly used by RBC and CNS
Liver Glycogen (1/3rd stored) - Used to maintain blood glucose
Muscle Glycogen (2/3rd stored)
Amount of exercise and dietary carbohydrate intake determines the amount
Used to produce ATP in the muscle during exercise
Diet and exercise influence glycogen stores in the muscle
During exercise, the body supplies glucose to the muscles from the stores of glycogen in the liver and in the muscles
First 20 minutes 1/5 of total glycogen used
After first 20 minutes, body shifts to FAT
At some point glycogen will be depleted. At this point person can experience “hitting the wall” = overwhelming fatigue.
Muscle glycogen repletion begins immediately after exercise and prepares the energy stores for the next workout!

6. The Effect of Exercise Intensity on Fuel Use6

7. Carbo-Loading
Carbohydrate loading is only effective for endurance events lasting longer than 90 minutes, such as marathons, triathlons, etc.
During intense, continuous endurance exercise, muscles will become depleted of glycogen after about 90 minutes. Carbohydrate loading is meant to store extra glycogen that your muscles can tap into once the normal stores are used up.
Combination of reduced training prior to event and increased carbohydrate intake. Various methods. 7

8. Proteins
The range is 1.2 to 1.6 g of protein per kilogram of body weight
Amount of protein used depends on intensity / duration of exercise
Protein g/kg/day
RDA for adults 0.8
Endurance athletes
Resistance Training
To become an energy source, proteins must first be degraded into amino acids. Nitrogen (NH2) component is removed then:
The carbon skeletons of the amino acids are
■ converted to acetyl CoA which enters the Krebs cycle
■ converted into pyruvate
■ others can be converted into oxaloacetate

9. Fats AT REST burn mostly fat & some CHO
When you exercise, the fat your muscles burn comes from the fatty deposits all over the body.
Desirable body weight may store 25 to 30 pounds of body fat; 1 pound of carbohydrate.
Consume low-fat foods prior to exercise and a low-fat (20- 25% of Calories) diet in general
MCT have been thought to be useful during exercise, but not proven, however, they are useful for malabsorption syndromes due to their direct absorption into the blood stream
Beta-Oxidation -- oxidizes fatty acids to acetyl CoA.
Acetyl CoA to TCA (Krebs Cycle) materials for ATP
Acetyl CoA - moves carbon atoms into energy pathway.
NADH, FADH -electron carriers

11. Fluid Needs and Exercise
Replenishing fluid lost during exercise accomplished by drinking fluid before, during, and after exercise; decreases risk of heat-related injury
Heat cramps, heat exhaustion, heat stroke
Sports drinks designed to enhance the body’s use of carbohydrate and water.
Should contain 4%-8% carbohydrates
The carbohydrate in a sports beverage serves 3 purposes during exercise:
Becomes an energy source
Helps maintain blood glucose
Helps increase the rate of water absorption from the small intestine, helping maintain plasma volume

12. Thermal Regulation and Hydration
The ability to keep the body cooled during exercise is key to exercise capacity and avoiding injury.
A lot of heat is generated in the body due to the inefficiencies of energy transfer to make ATP.
SWEATING creates the evaporative cooling system employed during exercise to keep core body temperature in functional range.
The core body temperature rises during exercise
If the core body temperature >104oF, exercise capacity diminishes and risk of thermal injury increases
Fluid, salt, and other components are lost in sweat during exercise – about a liter of fluid per hr. of exercise and 2.6 g of salt per liter
Salt (NaCl) is 40% sodium, ½ t salt replaces the sodium lost in 1 hour of vigorous exercise.

14. Body Temperature Regulation
RADIATION –bodies usually warmer than objects around them. Heat transferred from body's surface to objects “NEARBY” that are COOLER. NO DIRECT CONTACT!!
If environmental temperature is higher than body temperature, cannot lose heat by radiation!!
Heat carried from your internal organs to skin by the blood radiates heat from skin's surface.
CONDUCTION - Heat transferred from your body to any object or substance in “DIRECT CONTACT” with it.
Good conductors of heat like metal or light cotton clothing. Heat can pass easily through such objects
In cooler weather heat conduction can be minimized by wearing clothes made of wool or fur which are poor conductors of heat but good insulators. Heat cannot easily permeate such objects

15. Body Temperature Regulation
CONVECTION- Heat is transferred AWAY FROM THE BODY surface by the MOVEMENT OF THE AIR AROUND YOU.
The air close to your skin becomes warm and rises, allowing cooler air to take its place next to the skin.
EVAPORATION - Evaporation occurs when atoms or molecules escape from the liquid and turn into a vapor.
Sweat (liquid) wets the skin surface; body changes liquid to water vapor (gas); evaporation carries heat away.
humid conditions may cause sweat to drip off body rather than evaporate on the skin; sweat is useless as a coolant in humid environments.

16. Dehydration to Hydration
The fluid lost in sweat comes from the blood stream
The plasma volume is the fluid reserve for sweat
Fluid volume loss during aerobic exercise leads to dehydration
The sensation of thirst signifies 2% dehydration, cardiovascular and aerobic function is reduced.
5% dehydration, serious thermal injury risk. (heat exhaustion)
Body can absorb 1 liter of fluid per hour
Replacing fluids (cool, dilute, small, and frequent amounts) during strenuous exercise is important:
1 cup at 41oF, every minutes
Drink without thirst to avoid dehydration
Electrolytes (Na+, K+, Cl-) critical for body processes. Must replaced in addition to fluids

17. Consequences of Dehydration and Hydration
Importance of hydration during exercise
Cardiovascular demise during dehydration
Optimize muscle strength
Optimize aerobic capacity
Prevention of thermal injury such as: dizziness, cramping, fainting, heat exhaustion and heat stroke
Pool of fluid to draw upon for sweat loss is the blood stream.
The cardiovascular system is affected dramatically by fluid losses.
Plasma volume decreases
Osmolarity of the blood increases
Blood pressure goes down
Constriction of blood vessels
Increase in heart rate
Decrease in heart filling
Decrease in cardiac output
Decreased sweating
Increase in core body temperature