Ergogenic Aids: Caffeine

Caffeine

Characterization– Member of methylxanthine group of compounds• Mild stimulant that affects multiple organ systems

– Absorbed rapidly from the gastrointestinal tract– Blood half-life of 3 to 6 hours

Sources– Found in many food, beverage, and pharmaceutical sources– Occurs naturally in coffee beans, tea leaves, cocoa, and cola nuts

Caffeine Sources

Data from product labels and manufacturers, and National Soft Drink Association. 1997.aBrewing tea or coffee for longer periods slightly increases the caffeine content.bPrescription, 1 oz; 30 mL.Reprinted from Mc Ardle WD, et al. Sports and Exercise Nutrition, 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009:338.

Substance Caffeine content (mg)Beverages and foodsCoffeea

Coffee, Starbucks, decaf, 12 oz 10Coffee, Starbucks, grande, 16 oz 550Coffee, Starbucks, tall, 12 oz 375Coffee, Starbucks, short, 8 oz 250Caffe, Starbucks, Americano, grande, 16 oz 105Caffe, Starbucks, Americano, tall, 12 oz 70Caffe, Starbucks, Americano, short, 8 oz 35Caffe, Starbucks, latte or cappucino, grande, 16 oz 70Caffe Mocha, Starbucks, short (8 oz) or tall (12 oz) 35Espresso, Starbucks, 8 oz 280Brewed, drip method 110-150Brewed, percolator 64-124Instant 40-108Espresso 100Decaffeinated, brewed or instant; Sanka 2-5Coffe Frappuccino, Starbucks, grande, 16 oz 170

Tea, 5 oz cup*Brewed, 1 min 9-33Brewed, 3 min 20-46Brewed, 5 min 20-50Nestea Sweetened Lemon Ice Tea 20Iced tea, 12 oz; instant tea 12-36Green tea, 8 oz 30

ChocolateBaker's semi-sweet, 1 oz; Baker's chocolate chips, 1/4 cup 13Cocoa, 5 oz cup, made from mix 6-10Milk chocolate candy, 1 oz 6Sweet/dark chocolate, 1 oz 20Baking chocolate, 1 oz 35Chocolate bar, 3.5 oz 12-15Jello chocolate fudge mousse 12Ovaltine 0

Soft drinks7-Eleven Big Gulp Cola, 64 oz 190Jolt 100Sugar Free Mr. Pibb 59Mellow Yellow, Mountain Dew 53-54Tab 47

Table 1. Caffeine Content (mg) of Some Common Foods, Beverages, and Over-the-Counter and Prescription MedicationsSubstance Caffeine content (mg)

Coca Cola, Diet Coke, 7-Up Gold 46Shasta-Cola, Cherry Cola, Diet Cola 44Dr. Pepper, Mr. Pibb 40-41Dr. Pepper, Sugar Free 40Pepsi Cola 38Diet Pepsi, Pepsi Light, Diet RC, RC Cola, Diet Rite 36Red Bull, 8 oz 80

Frozen DessertsBen and Jerry's no fat coffee fudge frozen yogurt, 1 cup 85Starbucks coffee ice cream, assorted flavors, 1 cup 40-60Haagen-Dazs coffee ice cream, 1 cup 58Haagen-Dazs coffee frozen yogurt, fat free, 1 cup 42Haagen-Dazs coffee fudge ice cream, low fat, 1 cup 30Starbucks frappuccino bar, 1 bar (2.5 oz) 15Healthy Choice cappuccino, chocolate chunk, or cappuccino mocha fudge ice cream, 1 cup

8

Over-the-counter productsCold remedies

Dristan, Coryban-D, Triaminicin, Sinarest 30-31Excedrin 65Actifed, Contac, Comtrex, Sudafed 0

DiureticsAqua-ban 200Pre-Mens Forte 100

Pain remediesVanquish 33Anacin; Midol 32Aspirin, any brand; Bufferin, Tyelenol, Excedrin PM 0

StimulantsVivarin tablet, NoDoz maximum strength caplet, Caffedrine 200NoDoz tablet 100Enerjets lozenges 75

Weight control aidsDexatrim, Dietac 200Prolamine 140

Pain drugsb

Cafergot 100Migrol 50Fiorinal 40Darvon 32

Caffeine and General Health No consistent evidence for adverse effects on the cardiovascular system– Pre-existing heart arrhythmias or high blood pressure should limit consumption– Potential interactions with other compounds (eg, ephedrine) may increase risk of

side effects Sleeplessness and jitters are well-recognized side effects, especially in people

not used to caffeine Stomach irritation may occur with caffeinated beverages that increase

stomach acid No convincing links between caffeine and cancer or osteoporosis Stimulant effects of caffeine on metabolic rate are minor and should not greatly

affect weight control Coffee may help to protect against type 2 diabetes and diseases such as

Parkinson’s– Data are mainly observational and the relationships are not exceedingly strong

Abstinence or moderation of intake (≤ 2 cups per day) is advisable during pregnancy and lactation

Williams MH. Nutrition for Health, Fitness, & Sport. 9th ed. New York, NY: McGraw Hill; 2010:539-542.

Why Is Caffeine Possibly Ergogenic?

Increased free fatty acids, glycogen sparing– Associated with higher levels of cAMP in adipose cells• Adenosine receptor antagonism• Phosphodiesterase inhibition (at high doses)

Inhibition of glycogen phosphorylase enzyme– Less breakdown of glycogen

Links excitation to contraction in muscle cells– Via release of Ca++

Direct stimulation of central nervous system– Endorphin release causes decreased perception of effort

Stimulation of sodium/potassium pumps– Increased nutrient entry into cells by secondary active transport

Inhibition of phosphoinositide metabolism– Less signaling effects of insulin

Possibly other mechanisms as well

Abbreviation: cAMP, cyclic adenosine monophosphate. Magkos F, Kavouras SA. Caffeine use in sports, pharmacokinetics in man, and cellular mechanisms of action. Crit Rev Food Sci Nutr. 2005;45(7-8):535-562.

Effects of Caffeine on Substrate Oxidation During Exercise

Subjects: • 2 female, 7 male cyclists

Exercise: • Cycle to exhaustion at 80% VO2max

Design: • Crossover

Caffeine: • Decaffeinated or caffeinated coffee (330 mg caffeine) 1 hour before cycling

Time to exhaustion was nearly 15 min longer for caffeine vs placebo

Abbreviations: FFA, free fatty acid; SE, standard error; VO2max, maximal oxygen consumption; R, ratio; VCO2, carbon dioxide production.Reprinted from Costill DL, et al. Med Sci Sports. 1978;10(3):155-158.

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Effect of Caffeine on 500-m Split Times During a 1,500-m Swim

Subjects: • 7 male (72.3 kg), 4 female (57.9 kg) swimmers • Capable of swimming 1,500 m in < 25 minutes• All subjects consumed < 300 mg caffeine/week• All subjects abstained from caffeine for 48 hours before study

Design: • Randomized, double-blind, crossoverCaffeine: • 6 mg/kg body weight (BW) administered in a fruit juice drink 2.5 hours before the swim

• Placebo was fruit juice drink aloneReprinted from MacIntosh BR, et al. Can J Appl Physiol. 1995;20(2):168-177.

Subjects swam faster after caffeine

consumption and reported lower

perceived exertion

PlaceboCaffeine

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Effects of Different Doses of Caffeine on Performance

Subjects: • 9 well-trained cyclists• Caffeine users (100 to 250+ mg/day)• Abstained from caffeine for 3 days prior to exercise

Exercise: • Cycle to exhaustion at 80% VO2max

Caffeine: • 0, 5, 9, or 13 mg/kg BW• Caffeine given by capsule

Abbreviations: BW, body weight; VO2max, maximal oxygen consumption.Reprinted from Pasman WJ, et al. Int J Sports Med. 1995;16(4):225-230.

There was no dose response observed for the dose range evaluated

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mg caffeine/kg BW

*P < 0.05 placeboversus caffeine

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58 min 58 min59 min

Urinary Caffeine Levels With Different Doses of Caffeine

mg caffeine/kg BW

Abbreviations: BW, body weight; IOC, International Olympic Committee.Reprinted from Pasman WJ, et al. Int J Sports Med. 1995;16(4):225-230.

Only the 5-mg/kg BW dose always resulted in urine concentrations below previous IOC

limits

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What Is the Ergogenic Dose of Caffeine?

3 to 6 mg/kg BW associated with ergogenic benefits for endurance exercise– No further benefits with higher doses

May have more pronounced effects on non-users or regular users who abstain from caffeine for several days– These data are not always consistent– There are potential adverse effects in athletes who don’t regularly use

caffeine Recommended to try caffeine in practice before competition

conditions

Abbreviation: BW, body weight. Mc Ardle WD, et al. Sports and Exercise Nutrition, 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009:340-341.

Is Caffeine Permissible as an Ergogenic Aid? No longer listed by the World Anti-Doping Agency as a prohibited

substance– Remains on their Monitoring List

Still on the National Collegiate Athletic Association (NCAA) Banned Substance List at a dose that results in a urine concentration of 15 μg/mL– Equivalent to 9 to 13 mg/kg BW consumed 1 hour before event• Equals 630 to 910 mg caffeine/day for a 70-kg person– Roughly 6 to 9 cups of coffee

Abbreviations: BW, body weight; NCAA, National Collegiate Athletic Association.

Position of the International Society of Sports Nutrition Caffeine is effective as an ergogenic aid at 3 to 6 mg/kg BW– More effective when consumed in anhydrous state

Caffeine may– Enhance vigilance during extended exhaustive exercise or sleep deprivation– Be beneficial for sustained maximal endurance exercise, such as time trial

performance– Be beneficial for high-intensity exercise with intermittent activity occurring

over a long period of time (eg, team sports such as soccer or rugby) Data are equivocal regarding effects of caffeine on strength

and power Scientific literature does not support the notion that caffeine is a

diuretic during exercise

Abbreviation: BW, body weight.Goldstein ER, et al. J Int Soc Sports Nutr. 2010;7(1):5.