Ergogenic AidsChapter 11.ppt

1、Ergogenic Aids Chapter 11,Prepared by: Professor Steven Dion Jennifer Trompke & Erica Roux,2,Examining Ergogenic Aids,Androstenedione Caffeine Amino Acid Supplements L-Carnitine Creatine Alcohol,3,Androstenedione: A Nutritional Supplement or a Potentially Harmful Drug?,Androstenedione is an over-the

2、-counter “nutritional” supplement that several athletes consume. Most believe it will stimulate the production of endogenous testosterone, making them train harder, build muscle mass, and repair injury faster.,4,Androstenedione is similar to anabolic steroids. It is an intermediate or precursor horm

3、one between DHEA and testosterone, and aids the liver in synthesizing other biologically active steroid hormones. It is found in meat and extracts of some plants. Several Athletic Associations, Leagues, and Committees have banned its use because of its unfair competitive advantage and its health haz

4、ards.,5,Sport-related issues focus on: whether supplementation causes significant increases in muscular strength and power and whether any fitness increases actually transfer to improved performance in the diverse, precise motor skills required in baseball, ice & field hockey soccer, and golf.,6,Caf

5、feine,Caffeine comes from a group of lipid-soluble compounds called purines. They are found naturally in coffee beans, chocolate, cocoa beans, tea leaves, and cola nuts which are often added to carbonated beverages and nonprescription medicines 63 plant species contain caffeine in their leaves, frui

6、ts or seeds,7,In the U. S. 75% (14 million kg) of caffeine intake comes from coffee and 15% from tea. 1 cup of brewed coffee contains between 60 to 150mg of caffeine, instant coffee about 100mg, brewed tea between 20 and 50mg, and caffinated soft drinks about 50mg. 2.5 cups of percolated coffee cont

7、ains 250 to 400mg or between 3 & 6 mg per kg of body mass. The intestinal tract absorbs caffeine rapidly within 1hr.,8,9,Ergogenic Effects,Electrolyte balance and glucose availability are key factors that influence caffeines ergogenic effect. An ergogenic effect occurs with caffeine ingestion prior

8、to exercising. Consuming caffeine before exercise increased fat catabolism and reduced carbohydrate oxidation based on plasma glycerol and free fatty acid levels.,10,11,Proposed Mechanism for Ergogenic Action,Caffeine acts in two ways: 1) directly on adipose and peripheral vascular tissues. 2) Indir

9、ectly from caffeines stimulating epinephrine release from the adrenal medulla; epinephrine the acts as an antagonist of the adenosine receptors on adipocyte cells.,12,The adenosine receptors repress lipolysis. It then activates hormone-sensitive lipases to promote lipolysis and releases free fatty a

10、cids into the plasma. Caffeine produces analgesic effects on the central nervous system and enhances motor neuronal excitability. It also exerts a calming effect on neurons of the brain and spinal cord.,13,14,Effects Often Inconsistent,Individuals who maintain a high-carb intake show a blunted effec

11、t on free fatty acid mobilization. Coffee may antagonize the actions of caffeine. Athletes should omit caffeine-containing foods and beverages 4 to 6 days before competition to optimize caffeines potential for ergogenic benefits.,15,Effects on Muscle,Caffeine may act directly on muscle to enhance it

12、s capacity for exercise. It exerts a direct and specific ergogenic effect on skeletal muscle during repetitive low-frequency stimulation. It increases the sarcoplasmic reticulums permeability to calcium ions and influences the myofibrils sensitivity to calcium ions to augment excitation-contraction

13、coupling.,16,Warning about Caffeine,People who dont usually consume caffeine may experience undesirable side effects. Caffeine stimulates the central nervous system and causes headache, nervous irritability, insomnia, tremulousness, muscle twitching, elevated heart rate and blood pressure, and trigg

14、er premature left ventricular contractions.,17,Amino Acid Supplements and Other Dietary Strategies for an Anabolic Effect,Body builders, weight lifters, and fitness enthusiasts use amino acid supplements believing they boost the bodys natural production of the anabolic hormones testosterone, growth

15、hormone, insulin, or insulin-like growth factor to improve muscle size and strength to decrease body fat.,18,A Prudent Means To Possibly Augment an Anabolic Effect,Within exercised muscle fibers, resistance training generally stimulates both protein degradation and protein synthesis. Dietary modific

16、ations that increase amino acid transport into muscle raise energy availability, or increase anabolic hormones would theoretically augment the training effect within muscle by increasing the rate of anabolism or depressing catabolism.,19,L-carnitine,It is a short chain of coboxylic acid that contain

17、s nitrogen. It is a vitamin like compound found mostly in meat and dairy products. L-carnitine is vital for Norman metabolism; carnitine facilitates the influx of long-chain fatty acids in to the mitochondrial matrix. It becomes synthesized in the body by the liver and kidneys from methionine and ly

18、sine. Carnitines function can stall the accumulation of lactic acid and enhance exercise performance. About 95% of the bodys carnitine is located within muscle cells.,20,Rate of Fatty Acid Oxidation Affects Aerobic Exercise Intensity,Marketing for L-carnitine targets endurance athletes that believe

19、“metabolic stimulators” enhances fat burning and spares glycogen. Carnitine also appeals to body builders and other as a way to reduce body fat. No research supports ergogenic benefits, positive metabolic alterations, or body fat-reducing effects from L-carnitine supplementation.,21,Increasing intra

20、cellular L-carnitine level through dietary supplementation should/may promote fat oxidation during exercise and elevate aerobic energy transfer from fat breakdown while conserving limited glycogen reserves. Supplementation would be most beneficial under conditions of glycogen depletion, therefore ma

21、king the greatest demand for fatty acid oxidation.,22,Young and Middle Aged Men,(Normal carnitine intake is about 100-200 kg daily) Different muscle carnitine levels do not reflect capacity for aerobic metabolism.No L-carnitine deficit occurs during long-term exercise or heavy training.Individuals t

22、aking up to 2000 mg of L-carnitine per day during exercise did not affect the fuel mixture metabolized, or endurance performance, aerobic capacity, or exercise level for the onset of blood lactate accumulation.,23,Some Benefits,May act as a vasodilator in peripheral tissues, which possibly may enhan

23、ce regional blood flow and oxygen delivery. Could delay onset muscle soreness. Possibly experience significantly less post exercise muscle pain and tissue damage, indicated by lower plasma levels of muscle enzyme creatine kinase. The vasodilator property of L-carnitine may improve oxygen supply to d

24、amaged tissue, thus promoting clearance of muscle damage by products.,24,Creatine,Meat, poultry and fish are rich sources of creatine. These rich sources contain approximately 4-5 g of creatine per kg of food weight. The body synthesized only about 1 g of this nitrogen-containing organic compound da

25、ily, primarily in the kidney, liver, and pancreas forms the non essential amino acids arginine, glycine, and methionine. Adequate dietary creatine is important. About 95% of the bodys total creatine exists in skeletal muscle.,25,Creatine Supplements,Creatine supplement forms come in powder, tablets,

26、 capsules, and stabilized liquid form. Creatine supplements can be used in international competition since sports governing bodies dont consider creatine to be an illegal chemical substance. Relatively high doses remain high for weeks after only a few days of supplementation.,26,Benefits Under Certa

27、in Exercise Conditions,Power athletes believe that creatine supplementation: (1) Improves performance in muscular strength and power activities (2) Augments short bursts of muscular endurance, and (3) Provides for greater muscular over load in training.,27,Creatine doesnt just benefit weight lifters

28、 and body builders. Augmented short-term anaerobic power output capacity would also aid in sprint running, swimming, and cycling and jumping, football, volleyball, and soccer. Increased intramuscular PCr concentrations should also enable individuals to increase training intensity. Supplementation co

29、mbined with exercise training enhances high intensity running performance.,28,Effect on Body Mass,Body mass increases between .5 to 2.4kg when consuming creatine supplementations. This increase is in fat/bone-free body mass, not in total body water.,29,Creatine Loading,Users ingest 20 to 30g of crea

30、tine daily for 5 to 7 days. People who consume vegetarian-type diets show the greatest increase in muscle creatine levels because of the low creatine content in their diet. You should stop consuming caffeine when using creatine especially prior to competition. Caffeine blunts the ergogenic effect of

31、 creatine supplementation and counteracts the muscle creatine loading.,30,Alcohol,The strongest predictor of male use of alcohol as a teen are their best friends and partners habits. Men typically consume more alcohol than women. The liver can remove alcohol at the rate of 10 grams per hour = 1 serv

32、ing. Age, gender, body fat, and size influence blood alcohol levels.,31,Alcohol and Fluid Replacement,Alcohol exaggerates the dehydrating effect of exercise in a warm environment Decreases antidiuretic hormone release Acute alcohol consumption impairs psychomotor skills Alcohol may decrease strength, power, speed, local muscular endurance and cardiovascular endurance.,