Fundamentals of Exercise for Nutrition Module 4.5

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.

ATP energy production through glycolysis, the citric acid cycle, and the electron transport chain https://www.google.com/search?tbm=isch&q=glycolysis+%2C+kreb+cycle+ETC&ei=MWtjVZXrMJTioASUjoOoBw#imgdii=f9wNDJviHFD0YM%3A%3Bf9wNDJviHFD0YM%3A%3BARL_35HSSeon9M%3A&imgrc=f9wNDJviHFD0YM%253A%3ByJ08LSzCAirbWM%3Bhttps%253A%252F%252Fclassconnection.s3.amazonaws.com%252F558%252Fflashcards%252F183558%252Fpng%252Fpicture11328279654191.png%3Bhttp%253A%252F%252Fgalleryhip.com%252Fglycolysis-citric-acid-cycle-electron-transport-chain.html%3B1287%3B826

Fuels for Exercise Glucose Glycolysis Pyruvate to Acetyl CoA - aerobic – pyruvate (pyruvic acid) anaerobic process (no oxygen) lactic acid Citric Acid Cycle (Krebs Cycle) – aerobic oxaloacetate Electron Transport Chain- aerobic Major Players NADH, FADH- electron transporters (via hydrogen ions) Acetyl CoA- used to convey carbon atoms to citric acid cycle to be oxidized in energy production ATP-provides the energy to for cell operations

Glycolysis http://classes.midlandstech.edu/carterp/Courses/bio225/chap05/05-12_Glycolysis-2_1.jpg

Citric Acid Cycle – Kreb Cycle – TCA Cycle Oxaloacetate http://img.sparknotes.com/figures/1/186f53ba8ba05a8598a60d5a041b034f/citricacidcycle.gif

http://www. kirksville. k12. mo http://www.kirksville.k12.mo.us/khs/Teacher_Web/alternative/electrontransport.jpg

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 (1/3 is stored) - Used to maintain blood glucose Muscle Glycogen (2/3rd is 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.

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. 10

The Effect of Exercise Intensity on Fuel Use 11

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 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

Proteins Amount of protein used depends on intensity / duration of exercise Protein g/kg/day RDA for adults 0.8 Endurance athletes 1.2-1.6 Resistance Training 1.6-1.7 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

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

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 the core body temperature in a 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 hour of exercise, and 2.6 grams of salt per liter Salt (NaCl) is 40% sodium, ½ t salt replaces the sodium lost in 1 hour of vigorous exercise.

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

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. http://i.ytimg.com/vi/OQKlbDtPg2s/0.jpg

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 10-15 minutes Drink without thirst to avoid dehydration Electrolytes (Na+, K+, Cl-) critical for body processes. Must replaced in addition to fluids

Consequences of Dehydration and Hydration http://today.uconn.edu/wp-content/uploads/2012/02/iStock_000011177667Small.jpg http://weightwise.com/wp-content/uploads/dehydration.jpg Importance of hydration during exercise Cardiovascular demise during dehydration Optimize muscle strength Optimize aerobic capacity Prevention of thermal injury which include 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 the blood vessels Increase in heart rate Decrease in heart filling Decrease in cardiac output Decreased sweating Increase in core body temperature