Welcome to FCSN/PE 446 Sports Nutrition and Weight Control David L. Gee, PhD

Energy Systems for Exercise FCSN/PE 446 Dr. David L. Gee Professor of Food Science and Nutrition

Human Energy Systems n ATP-PC System adenosine triphosphate phosphocreatine n Lactic Acid System anaerobic glycolytic pathway n Oxygen System aerobic metabolic pathways

ATP-PC Energy System ATP – Energy for muscle contraction

ATP-PC System n ATP n highest rate of energy production n lowest total energy capacity n all energy for muscle contraction must flow through ATP

ATP-PC System n Phosphocreatine n Rapid equilibrium with ATP/ADP n Highest rate of energy production n Lowest total energy production

Creatine as an Ergogenic Aid n Claims for creatine (monohydrate) EAS web page (2002) n “...may boost muscle size and strength, increase lean body mass, delay fatigue, and speed muscle recovery after exercise.”

Creatine as an Ergogenic Aid n Creatine Loading Protocol n grams/day for 3-5 days n 3-5 grams/day for maintenance n or 3-5 grams/day for gradual loading n typical dietary creatine = 1g/d n cost (EAS Phosphagen, 3/02) $16 for loading $36 per month for maintenance ($432/yr)

Is Creatine an Erogenic Aid? n Levels of evidence for ergogenic effects n 1. Is there a sound hypothetical mechanism explaining potential ergogenic effects?

Levels of evidence for ergogenic effects n 2. Are there biochemical indicators that suggest ergogenic effects? n 3. Are there studies that demonstrate improvement of physical performance?

Creatine as an Ergogenic Aid n Theoretical Basis n creatine phosphate levels limit ATP production during maximal exercise n Therefore, supplementation will increase cellular CP levels and increase high intensity performance

Creatine as an Ergogenic Aid n Biochemical evidence n supplementation of creatine does result in increased muscle creatine concentration 16% increase in muscle creatine after 6 20g/d –Hultman et al, JAP 81: (1996)

Creatine as an Ergogenic Aid n Scientific Performance Evidence n Ideal investigation: RCT: Randomized Controlled Trials –double blind - placebo trials n typically increases muscle Cr n typically results in increased LBM kg water or protein ? may impair performance

Creatine supplementation enhances muscular performance during high-intensity resistant exercise. JADA 97: (1997) n 14 active men randomized, double blind w/ placebo 25g Cr/day for 6 days Tested on three occasions –Before supplementation –After 6 days of placebo capsule supplementation –After 6 days of either placebo or creatine capsule supplementation bench press (5 sets of 10 reps to failure) squat exercise (5 sets of 10 reps to failure)

A.The placebo effect: by set 4 & 5, athletes taking placebo after T2 and T3 have more repetitions. B.The creatine effect: by set 3, 4, & 5, athletes consuming Cr perform better than pre-supp (T1) or placebo (T2)

A.Placebo effect only seen in set 2 B.Creatine improves jump- squat peak power output in all sets over pre-supp period (T1) and over placebo (T2) in sets 1, 2, 3, & 4

Creatine supplementation enhances muscular performance during high-intensity resistant exercise. JADA 97: (1997) n Conclusion: One week of creatine supplementation (25g/d) enhances muscular performance during repeated sets of bench press and jump squat exercise.

Creatine supplementation does not improve sprint performance in competitive swimmers. MSSE 28: (1996) n 28 trained competitive swimmers randomized, double-blind placebo trials 5 days 20g creatine/day or placebo 25, 50, 100 meter trials, best stroke n Results no significant differences in performance times between trials or groups no effect of Cr on post-exercise blood lactate

Creatine as an Ergogenic Aid n Many, but not all studies show increases in power output n generally seen in high power, repetitive exercise tests

Creatine as an Ergogenic Aid n No (?) long term safety tests No consistent reports of adverse affects n Few studies with adolescents n Recommendations?

ACSN Consensus Statement Creatine Supplementation n MSSE March 2000 n Oral Cr increases muscle C~P n 3g/d over time = 20g/d loading n “Exercise performance involving short periods of extremely powerful activity can be enhanced, especially during repeated bouts of activity.”

ACSN Consensus Statement Creatine Supplementation n “There is no definitive evidence that Cr supplementation causes GI, renal, and/or muscle cramping” n “…Cr exhibits small but significant physiological and performances changes…are realized during very specific exercise conditions” n “”…apparent high expectations…are inordinant.”

Creatine as an Ergogenic Aid Miscellaneous information n Creatine kinase ineffective as oral supplement blood levels indicate muscle damage n Creatinine waste product of creatine metabolism blood levels reflect renal function urine levels reflect –Total muscle mass –Dietary intake of creatine

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Dietary Supplements as Ergogenic Aids: Let the Buyer Beware! n Dietary Supplement Health Education Act (DSHEA) n Labeling of dietary supplements follow same laws as for foods (NLEA). Only approved health claims allowed “structure/function” claims allowed n Unlike pharmaceutical drug regulations No proof of safety required No proof of effectiveness required No effective regulation of product contents or purity

Dietary Supplements: The NFL Player’s Association Recommendation n As the Policy clearly warns, supplements are not regulated or monitored by the government. This means that, even if they are bought over-the-counter from a known establishment, there is simply no way to be sure that they : (a) contain the ingredients listed on the packaging; (b) have not been tainted with prohibited substances; or (c) have the properties or effects claimed by the manufacturer or salesperson. n Therefore, if you take these products, you do so AT YOUR OWN RISK! The risk is at least a 4-game suspension without pay if a prohibited substance is detected in your system. For your own health and success in the League, we strongly encourage you to avoid the use of supplements altogether, or at the very least to be extremely careful about what you choose to take.

NCAA: Permissible Nutritional Supplements NCAA Bylaw (2000) (web page link) n Supplements NCAA institutions can provide to athletes Non-muscle building nutritional supplements –Vitamins and minerals –Energy bars –Calorie replacement drinks (Ensure, Boost) –Electrolyte replacement drinks (Gatorade, Powerade) n Non-Permissible creatine Amino acids Carnitine Protein-powders and others

Lactic Acid System n Anaerobic glycolysis n Uses muscle glycogen, blood glucose, liver glycogen as substrates (not FAT or PRO) n High rate of ATP energy production n Primary fuel in sprint-type activities (a few seconds - few minutes)

Lactic Acid System n Important when: n Activity longer than a few seconds creatine-P depleted/limited n Activity too intense for aerobic metabolism oxygen delivery limited –limited rate of O 2 : uptake in lung transport and delivery to muscle cell transport and delivery to mitochondria

Lactic Acid System n Lactic acid is the end product n Low total energy capacity lactic acidosis Inhibits glycolytic enzymes n Training effects improved aerobic capacity reducing lactate production improved removal of lactate n Ergogenic aids bicarbonate loading

Oxygen Energy System

Oxygen Energy Systems n Aerobic carbohydrate metabolism glycolysis, Krebs cycle, electron transport system n lower rate of ATP energy production n high total energy capacity n primary source of energy for higher intensity endurance events (~< 30 min)

09.06 Aerobic Respiration Overview Slide number: 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glucose Plasma membrane Extracellular fluid Mitochondrion Cytoplasm

Glucose Plasma membrane Extracellular fluid Aerobic Respiration Overview Slide number: 4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mitochondrion Cytoplasm PyruvateGlycolysis ATP NADH Acetyl-CoA

Glucose Plasma membrane Extracellular fluid Aerobic Respiration Overview Slide number: 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mitochondrion Cytoplasm PyruvateGlycolysis ATP NADH ATP H2OH2O O2O2 Electron transport system ATP NADH CO 2 Krebs cycle NADH Acetyl-CoA

Oxygen Energy Systems n Fat oxidation Beta-oxidation, Krebs cycle, Electron transport system n Lowest rate of ATP-energy production n Highest total energy capacity n Primary source of energy during lower intensity endurance events (~>30 min)

Oxygen Energy Systems n Protein oxidation Amino acid oxidation, Krebs cycle, Electron transport system n Low rate of ATP-energy production n Limited total energy capacity n significant source of energy during long endurance events

% Contribution of Aerobic and Anaerobic Energy Sources

Human Energy Stores Sources of energy for energy systems n ATP-PC n Carbohydrates Muscle glycogen Blood glucose Liver glycogen

Human Energy Stores n Fats - Triglycerides Adipose triglycerides Muscle triglyceride n Hormone sensitive lipase Activity enhanced with caffeine n Ketone bodies partially oxidized fatty acids produced in liver, burned in muscle significant source of energy during prolonged endurance exercise

Human Energy Stores n Proteins n direct muscle oxidation (branched chain amino acids) n gluconeogenesis in liver from amino acids

Exercise Energy Metabolism: n Examples of experimental data

Exercise Energy Metabolism: Examples of experimental data

Example 1: Metabolic Fuels During Intense Exhaustive Exercise n 3 one minute sprints with one minute rest n muscle needle biopsy prior to 15 sec post-exhaustion (exhaustion) 30 minutes post-exhaustion (recovery)

Example 1: Metabolic Fuels During Intense Exhaustive Exercise

Key Points n In repeated one minute sprints Lactic acid system primary source of fuel [lactic acid] increases 30-fold resulting in lactic acidosis ATP & C~P are regenerated quickly after exercise Elevated lactate seen 30 minutes after exercise

Example 2: Glycogen Utilization During Endurance Exercise n Protocol Trained and untrained runners Treadmill running at ~ 70% VO2 max Run to exhaustion Measure muscle glycogen content every 20 minutes until exhaustion

Example 2: Glycogen Utilization During Endurance Exercise

Key Points Glycogen primary source of fuel in exercise lasting minutes Glycogen depletion associated with fatigue Rate of glycogen utilization rate higher early in exercise, lower late in exercise Utilization of glycogen lower in trained athletes

Example 3: Glycogen Degradation Rate During Exercise n Protocol Trained and untrained subjects Treadmill running at different % VO2 max Muscle biopsies to determine rate of muscle glycogen utilization

Example 3: Glycogen Degradation Rate During Exercise

Key Points n Rate of glycogen utilization directly related to intensity of exercise n Trained athletes utilize glycogen at lower rates than untrained subjects at same relative %VO2 More efficient delivery of oxygen and mobilization/oxidation of stored fats.

Example 4: Effect of Glycogen Level on Rating of Perceived Exertion n Protocol Trained runners Treadmill test at %70% of VO2max Muscle biopsies for glycogen determination RPE evaluation

Key Points n Glycogen utilization rate highest early in exercise n Muscle glycogen concentration inversely related to rating of perceived exertion

Example 5: Effect of Initial Muscle Glycogen Levels and Endurance n Protocol Fed trained athletes diets for 4 days either –Low (10%) –Moderate (50%) –high carbohydrate (85%)diets Treadmill running at 65% VO2max Muscle biopsy for glycogen analysis prior to treadmill run

Example 5: Effect of Initial Muscle Glycogen Levels and Endurance Low carb diet Moderate carb diet High carb diet

Key Points Initial Glycogen Levels and Endurance n During treadmill running, time to exhaustion is correlated with initial muscle glycogen content n Muscle glycogen content is affected by diet High carb diets promote glycogen storage

Example 6a: Muscle Glycogen and Soccer Performance (Agnevik, 1970)

Example 6b: Muscle Glycogen and Soccer Performance Saltin, 1973

Key Points Diet and Soccer Performance n Glycogen depletion is possible during soccer play n Initial glycogen content affects time spent running and total active time High glycogen allows for more running and total activity during soccer games

Example 7: Effect of Successive Days of Intense Training on Glycogen Content Costill & Miller (1980) n Trained endurance runners n 3 successive days of running 10 miles at 80% of VO 2 max n Dietary intake of CHO 58% of Calories 70% of Calories

Example 7: Effect of Successive Days of Intense Training on Glycogen Content Costill & Miller (1980)

Key Points: Effect of Successive Days of Intense Training on Glycogen Content n Glycogen depletion can occur with successive days of intense training Even when individual training day is not glycogen depleting n High carbohydrate diets promote replacement of glycogen used during exercise Helps prevent glycogen depletion during successive days of training

Metabolic Causes of Fatigue During Exercise. Table 3.9 (Williams) n Decreased Levels of Energy Substrates n decreased phosphocreatine levels n decreased muscle glycogen n decreased blood glucose hypoglycemia

Metabolic Causes of Fatigue During Exercise. Table 3.9 (Williams) n Decreased Levels of Energy Substrates (cont.) n decreased blood branch-chain amino acids Significant source of energy for muscle during endurance exercise Central Fatigue Hypothesis (increased formation of depressant neurotransmitters) –Decreased blood BCAA during exercise –Increase blood tryptophan:BCAA ratio –Shared blood:brain barrier transport system –Increased brain tryptophan –Increased synthesis of serotonin from tryptophan –Increased feeling of fatigue

Metabolic Causes of Fatigue During Exercise. n Disturbed Acid-Base Balance lactic acidosis n Decreased Oxygen Transport decreased blood volume due to dehydration High altitudes Nutritional anemias

Metabolic Causes of Fatigue During Exercise. n Increased Core Body Temperature dehydration environmental conditions n Disturbed Electrolyte Balance high sweat loss no electrolyte replacement