Protein for Sports—NewData and NewRecommendationsTim N. Ziegenfuss, PhD,1 Jamie A. Landis, MD, PhD, CISSN,2 and Robert A. Lemieux3

1The Center for Applied Health Sciences, Fairlawn, Ohio; 2Lakeland Community College,Kirtland, Ohio; and 3Kent State University, Kent, Ohio

S U M M A R Y

ESTIMATION OF OPTIMAL PROTEIN

AND/OR AMINO ACID INTAKE FOR

PHYSICALLY ACTIVE INDIVIDUALS

HAS BEEN HISTORICALLY PROB-

LEMATIC BECAUSE (A) SUBJECTS

CONSUMING THE SAME ABSO-

LUTE AMOUNT OF PROTEIN

COULD CONSUME DIFFERENT

AMOUNTS AND TYPES OF AMINO

ACIDS, (B) THE TIMING OF INGES-

TION (PRE VERSUS POST EXER-

CISE) ALTERS PROTEIN KINETICS

(SYNTHESIS VERSUS BREAK-

DOWN), AND (C) THE ADDITION OF

NONPROTEIN ENERGY (CARBO-

HYDRATE) AFFECTS PROTEIN

KINETICS.

INTRODUCTION

In the past, exercise scientists andcoaches have often debated theamount of protein that athletes

should eat to optimize gains in strengthand lean mass. Recently, it has becomeclear that quality (i.e., the type ofprotein) and timing (i.e., when anathlete eats relative to the exercisestimulus) trump overall protein intake,particularly in athletes who alreadyconsume adequate energy and proteinin excess of the recommended dietaryallowance (RDA). In this regard, al-though many researchers and authorshave made suggestions regarding pro-tein intake (which typically range from1.2 to 2.0 g/kg body mass per day), thisbrief review will attempt to synthesize

newer data and make specific recom-mendations regarding periworkoutsupplementation with essential aminoacids/protein and carbohydrates.

Several recent peer-reviewed studieshave investigated the influence ofnutrition and resistance exercise onmuscle protein accretion and, to a lesserextent, cellular signaling in humanskeletal muscle. Net protein balanceis quite obviously the arithmetic dif-ference between muscle protein syn-thesis (MPS) and muscle proteinbreakdown (MPB). Research to dateindicates that the magnitude of changein MPS is 10- to 20-fold greater thanMPB; therefore, strategies that increaseserum amino acid levels (particularlythe essential amino acids) shouldmaximize the anabolic response toresistance training. In this regard, a foodprotein has generally been considered‘‘complete’’ if it contains all 9 essentialamino acids and is theoretically bettersuited for tissue growth and repair(Table).

However, the phenomenon of MPShas recently been subjected to both anincreased scientific scrutiny and a morerefined precision of investigative tech-niques. For example, because MPS isnot simply regulated by an unadorned‘‘on/off’’ switch, studies have selec-tively examined the importance ofinfluential and indicative factors suchas protein turnover, nitrogen balance,essential amino acid ingestion, choiceof protein (e.g., milk versus soy),and most recently, the cellular and

molecular mechanisms regulating pro-tein turnover, for excellent reviews, seereferences (3,10,12). This latter aspectof muscle physiology may be some-what novel to many readers; therefore,a simplified schematic highlightingwhat are thought to be the mostimportant MPS molecular pathwayintermediates is included (Figure). Itshould be noted that other signalingpathways very likely contribute to theoverall adaptive (anabolic) responses inmuscle, but their discussion is beyondthe scope of this article.

MILK BEATS SOY AS APOSTEXERCISE ANABOLIC AGENT

Eight young men who regularly en-gaged in resistance exercise (i.e.,trained at least 4 days per week) werestudied in a crossover design usingunilateral resistance exercise (5). Aftera standardized breakfast, arterial andvenous blood and muscle biopsysamples were obtained, and subjectscompleted a standardized bout ofresistance training (4 sets 3 10 repe-titions at 80% of maximum on the legpress, leg curl, and leg extension,interspersed with 2-minute rest peri-ods). Immediately thereafter, a secondseries of blood and muscle sampleswere obtained. Subjects then ingested500 mL of nonfat milk or an isoni-trogenous, isoenergetic, macronutrient-matched soy beverage providing 745 kJ

KEY WORDS :

sports nutrition; protein; amino acids;nutrient timing; lean mass

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(178 kcal), 23 g carbohydrate, 18 gprotein, and 1.5 g fat. After drinkconsumption, serial samples of arterialand venous blood, along with musclebiopsies were obtained every hourthereafter for 3 hours. These measure-ments, along with pulsed Doppler

ultrasonography and primed constantinfusion metabolic tracers, allowed thecalculation of amino acid uptake acrossthe exercised leg and muscle fractional(protein) synthetic rates. Results in-dicated that although both soy andnonfat milk both increased net proteinbalance, the increase from nonfat milkwas significantly greater. Specifically,MPS rates were 34% higher afterconsumption of nonfat milk. Interest-ingly, because the essential amino acidcontent of the 2 drinks was similar(i.e., approximately 7.5 g), the research-ers proposed that soy protein, becauseof its more rapid rate of digestion, ledto a preferential synthesis of serumproteins and urea rather than muscleprotein.

KEY POINT

Milk protein promotes greater gains inmuscle accretion compared with soyprotein when ingested immediatelyafter resistance exercise (5).

TEN GRAM OF WHEY PROTEINSTIMULATES MUSCLE PROTEINSYNTHESIS

Eight healthy resistance-trained men(i.e., approximately 6 years of weighttraining experience) performed 2 trialsin random order to determine theeffect of postexercise consumption ofcarbohydrate (21 g fructose + 10 g

maltodextrin) versus carbohydrate plusprotein (21 g fructose + 10 g wheyprotein isolate [containing 4.2 g essen-tial amino acids]) on MPS (9). After anovernight fast, subjects completed4 sets of 8–10 repetitions at 80% ofmaximum for the leg press and legextension exercise. Arterial and venousblood samples, muscle biopsies, andpulsed tracer injections were used tocalculate rates of mixed MPS at restand after exercise. Not surprisingly,insulin levels peaked 30 minutes afteringestion during both trials, and aminoacid concentrations peaked 60 minutesafter ingestion during the carbohydrateplus protein trial. During the carbohy-drate plus protein trial, mixed MPStended to be higher at rest (p , 0.06)and was significantly higher during thepostexercise period compared withthat during the carbohydrate trial.The authors concluded that a minimaldose of whey protein (10 g), whencombined with 21 g of fructose, issufficient to induce a 2-fold rise inMPS in young men. However, they didacknowledge that their protein dose(which contained only 4.2 g of essentialamino acids) may have been suboptimalbecause other researchers have notedthat at least 10 g (and as high as 20 g) ofessential amino acids are necessary tomaximally stimulate MPS.

TableAmino acids

Essential aminoacids

Nonessentialamino acids

Histidine Alanine

Isoleucine* Arginine†

Leucine* Asparagine

Lysine Aspartic acid

Methionine Cysteine†

Phenylalanine Glutamic acid

Threonine Glutamine†

Tryptophan Glycine†

Valine* Proline†

Serine

Tyrosine†

*Branched-chain amino acid.

†Conditionally essential amino acid.

Figure . Simplified schematic of major molecular factors involved in the regulation of skeletal muscle protein synthesis. mTORC1:a complex composed of mTOR (mammalian target of rapamycin), regulatory associated protein of mTOR (aka Raptor),mammalian LST8/G-protein b-subunit–like protein (mLST8/GbL), and the recently identified partner PRAS40. S6K1 = p70-S6 kinase 1. 4E-BP1 = eukaryotic initiation factor 4E (eIF4E) binding protein.

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Protein for Sports

KEY POINT

Although not an optimal dose, 10 g ofwhey protein (about half scoop of mostcommercial protein powders) is suffi-cient to increase MPS in young men (9).

DOSE-RESPONSE EGGPROTEIN STUDY

It has been well established that theanabolic effects of resistance exerciseare enhanced when protein or essentialamino acids and/or carbohydrate areprovided in the periworkout period.Using each subject as their owncontrol, researchers recently examinedthe dose-response effects of whole eggprotein in 6 young fasted men whocompleted an acute bout of resistancetraining (i.e., 4 sets 3 8–10 repetitionseach of leg press, leg extension, andleg curl) and then ingested 0, 5, 10, 20,or 40 g of whole egg protein (8).Using a primed constant infusion of13C-leucine, venous and arterial bloodsamples, and repeated muscle biopsies,measurements of mixed muscle frac-tional synthesis rates were found toincrease in a dose-dependent mannerup to 20 g, where values reacheda plateau at approximately 93% abovethe baseline (i.e., fasted) condition. Atthe 40-g dose, no further increase inmixed MPS was noted, and insteada significant stimulation of whole body,leucine oxidation occurred. This studyshowed that amino acid availability inthe postexercise period is the key factorin driving muscle growth and that 20 gof whole egg protein, which is equiv-alent to approximately 8.6 g of essentialamino acids, is sufficient to maximallystimulate mixed MPS after lower-bodyresistance exercise. It is important tonote that no carbohydrates were givenin this study, and the benefit ofcarbohydrate ingestion on proteinkinetics is a decrease in MPB (whichthen magnifies the increase in netprotein balance).

KEY POINT

If only protein is consumed in thepostexercise period (which is notrecommended, see Practical Applica-tions), a 20-g dose of egg protein willmaximize MPS (8).

AGING DELAYS MUSCLE PROTEINKINETIC RESPONSES

After the age of 30, muscle loss occursat a rate of at least 5% per decade.Although resistance training is aneffective stimulus for lean mass accre-tion and helps attenuate age-relatedmuscle loss, its effect on stimulatingmuscle growth is blunted in olderversus younger adults. Similarly, lowdoses of essential amino acids result inlower net MPS in older versus youngermen. A recent study compared theeffects of high-dose essential aminoacids (20 g) on anabolic signalingproteins in 7 young (average age =29.7 years) versus 6 old (average age =70.0 years) men (4). Subjects com-pleted 8 sets 3 10 repetitions of legextension exercise interspersed with 3-minute rest periods. Continuous in-fusion metabolic tracers and repeatedbiopsies revealed that younger menincreased their rates of fractional(mixed) MPS from 1 to 6 hours afterexercise, whereas older men onlynoted a significant increase from 3 to6 hours after exercise. Researchersspeculated that the reduced anabolicsignaling effects were because ofa lower insulin response (or impairedinsulin signaling) in the older men.

KEY POINT

Anabolic signaling in young subjectsis quicker and more pronounced thanthat in old subjects when 20 g ofessential amino acids are administeredafter acute resistance exercise (4).

WHEY ISOLATE BEATS CASEINFOR STRENGTH AND SIZE GAINS

Whey protein is currently consideredto be one of the highest qualityproteins available, particularly wheyisolate, which is rapidly digested andcontains high levels of essential aminoacids and almost no lactose (i.e.,,1.0%). Casein, which makes upapproximately 80% of bovine milkprotein, is digested more slowly andcontains approximately 10–20% lessessential amino acids per gram ofprotein. A landmark study publishedin 2006 reported that 13 recreationalbodybuilders who supplemented theirdiet with 1.5 g of whey protein isolate

per kilogram of body mass per daygained significantly more lean mass(approximately 4.2 kg) and strength(approximately 23 kg in the squat, 30kg in the bench press, and 15 kg in thelat pull-down) than subjects ingestingthe same amount of casein duringa supervised 10-week resistance train-ing program (2). Subjects in the wheyisolate group also lost 1.4 kg of bodyfat, whereas values for subjects in thecasein group did not change. It shouldbe noted that the total protein dosewas divided into 4 equal servingsand consumed throughout the day(i.e., breakfast, lunch, posttraining,and dinner).

KEY POINT

During resistance exercise training, sup-plementation with whey isolate leadsto significantly greater gains in leanmass and strength and significantlygreater loses of body fat compared withsupplementation with casein (2).

NUTRIENT TIMING ENHANCESADAPTATIONS TO RESISTANCETRAINING

In the past, dietary recommendationsfor athletes targeted daily amounts forthe intake of total energy, carbohy-drates, proteins, and fats, but littleimportance was placed on when mealswere consumed relative to training.A classic study demonstrating thebenefits of periworkout nutrition or‘‘nutrient timing’’ on muscle fiberhypertrophy, strength, and body com-position during training was performedby Cribb and Hayes (1). In a single-blind randomized design, 17 youngresistance-trained men were matchedfor strength and placed into 1 of 2groups; the PRE-POST (preworkoutand postworkout) group consumed 1gram per kilogram of body mass ofa nutrient mixture containing glucose,whey isolate, creatine monohydrate,and a small amount of fat immediatelybefore and after resistance exercise(e.g., an 80-kg participant consumed34 g glucose, 32 g whey isolate, 5.6 gcreatine, and 0.4 g fat.). The morningand evening (MOR-EVE) group con-sumed the same dose of the samesupplement before breakfast and before

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retiring to bed. After 10 weeks ofsupervised resistance training, thePRE-POST group demonstrated sig-nificantly greater increases in lean bodymass, 1 repetition maximum (RM)strength in 2 of 3 exercises (benchpress and squat), type II muscle fibersize, and contractile protein content.This study highlights the notion thatthe timing of ‘‘meals’’ surrounding theworkout period has a tremendousimpact on adaptive responses to resis-tance training.

KEY POINT

It is not just what you eat, but when youeat it, that determines the overall successof a resistance training program (1).

PRE- OR POSTINGESTION OFWHEY PROTEIN YIELDS SIMILAREFFECTS ON MUSCLE PROTEINBALANCE

Two groups of healthy participantswere randomly assigned to ingest 20 gof whey protein immediately beforeor 1 hour after the performance of 10sets3 8 repetitions of leg extensions at80% of 1RM (11). Muscle biopsies fromthe vastus lateralis were taken to mea-sure intracellular amino acid concen-trations, and blood flow was measuredusing indocyanine green infusion.Before exercise, background bloodsamples for insulin concentration weretaken, and additional arterial bloodsamples for insulin analysis also werecollected periodically throughout theprotocol: 120, 150, 180, 240, and 300minutes after exercise. Arteriovenoussamples were taken before and atregular intervals after exercise, up to300 minutes, to calculate net muscleprotein balance. Arterial amino acidconcentrations were elevated byapproximately 50%, and net aminoacid balance switched from negativeto positive after ingestion of protein ateither time point. Amino acid uptakewas not significantly different betweenconditions when calculated from thebeginning of exercise or from the timeof ingestion of each whey solution.

KEY POINT

Unlike essential amino acids, ingesting20 g of whey protein either before or 1

hour after resistance exercise has similareffects on muscle protein balance (11).

WHEY PLUS CASEIN TRUMPSCARBOHYDRATE

Nineteen healthy but previously un-trained men were randomly assignedto supplement their diet with either20 g of protein (14 g of whey andcasein protein, 6 g of free amino acids)or 20 g of dextrose 1 hour before andafter resistance exercise (14). Bothgroups completed a 4-d/wk trainingprogram that included 2 upper- and2 lower-body workouts per week. Theexercise regimen incorporated theprinciples of overload and progressiveresistance, using 3 sets of 6–8 repeti-tions at 85–90% of the 1RM. Bloodsamples (for insulin-like growth factor-1 (IGF-1) and insulin) and vastuslateralis muscle biopsies (for variousmarkers of muscle anabolism) wereobtained before and after 10 weeks oftraining. Results indicated that subjectsin the protein/amino acid blend grouphad significantly greater increases intotal body mass, fat-free mass, thighmass, muscle strength, serum IGF-1,IGF-1 messenger RNA (mRNA), ma-jor histocompatibility complex I andIIa expression, and myofibrillar protein.

KEY POINT

A 10-week heavy resistance trainingprogram combined with the ingestionof a blend of whey and casein proteinplus free amino acids is more effectivethan an isocaloric carbohydrate pla-cebo for improving muscle strength,lean mass, and markers of muscleanabolism (14).

RESISTANCE TRAINING ANDPROTEIN INGESTION POSITIVELYAFFECTS GENE EXPRESSION

A recent study investigated the long-term adaptations of adding a high-quality protein to the ‘‘normal diet’’ ofhealthy males undergoing resistancetraining (6). Thirty-one male partici-pants were randomized into proteinsupplementation, placebo, and controlgroups. Measurements of muscle cross-sectional area (via magnetic resonanceimaging) and muscle force production(via dynamometry) were made before

and after 21 weeks of heavy resistancetraining (i.e., more than 40 bouts oflower-body resistance exercise). Forexamination of acute changes, musclebiopsies were taken from the vastuslateralis before and at 1 hour and 48hours after 5 3 10 repetitions of legpress exercise. The examination ofchronic changes was made via anadditional biopsy after 21 weeks ofresistance training. Protein supplemen-tation (15 g of whey) or a nonenergeticplacebo was provided to the partic-ipants both before and after each boutof training. Results demonstrated thatsubjects in the protein group notedsignificantly greater increases in vastuslateralis cross-sectional area. Significantincreases were also noted in musclehypertrophy–related gene expressionboth acutely and chronically. Also,protein intake seemed to prevent the1-hour post–resistance exercise de-crease in myostatin, the satellite celldifferentiation regulator myogenin, andmRNA expression but did not affectother myostatin-related factors such asactivin receptor IIb, p21, follistatin-related gene (FLRG), muscle atrophyF-box (MAFbx), or MyoD expression.

KEY POINT

Long-term whey protein intake beforeand after resistance exercise alters ana-bolic signaling in a manner that is advan-tageous for muscle hypertrophy (6).

PROTEIN PLUS CARBOHYDRATEAUGMENTS ANABOLIC SIGNALING

The increase in MPS in response toan acute bout of resistance exerciseoccurs before changes in musclemRNA become apparent (i.e., post-transcriptionally). Currently, activationof the mTOR/PI3K signaling pathwayis considered to be one of the keysin controlling the magnitude of theanabolic response in muscle. Sevenhealthy, untrained, male participantswere randomly assigned to 2 crossoverexperiments to determine the impactof carbohydrate with or without addedprotein on markers of anabolic signal-ing in muscle (7). Before, immediatelyafter, and 1 hour after a single boutof lower-body resistance exercise

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Protein for Sports

(8 sets 3 10 repetitions of leg exten-sion), subjects consumed a carbohy-drate beverage (0.3 g/kg body mass)either with or without added proteinhydrolysate (also 0.3 g/kg body mass).Muscle biopsies were taken from thevastus lateralis before and immediatelyafter exercise and after 1 hour and4 hours of postexercise recovery todetermine the phosphorylation (acti-vation) status of the muscle proteingrowth markers 4E-BP1, S6K1, and S6.Immediately after resistance exercise,there was significantly more phosphor-ylation of 4E-BP1 in the carbohydrateplus protein trial. The initial phosphor-ylation of S6K1 was substantially in-creased after exercise and remainedelevated during recovery with nodifferences between treatments. How-ever, the second (activating) phosphor-ylation of S6K1 was significantly higherafter exercise only in the carbohydrateplus protein trial. During the recoveryperiod, the S6K1 phosphorylationremained significantly higher in thecarbohydrate plus protein trial. Thephosphorylation of S6 was signifi-cantly higher after exercise and duringrecovery in the carbohydrate plusprotein trial compared with that inthe carbohydrate only trial.

KEY POINT

This elegant study demonstrates thatthe combination of dietary carbohy-drate and protein enhances the acti-vation of muscle protein growthmarkers (S6, S6K1, and 4E-BP1)during the recovery from resistancetype exercise (7).

MILK BEATS SOY ANDCARBOHYDRATES DURINGRESISTANCE TRAINING

A group of 56 healthy, young, novice,male weightlifters were trained 5 daysper week for 12 weeks using a split-body resistance exercise program (13).Participants were randomly assigned toconsume fat-free milk protein, fat-freesoy protein, or a carbohydrate controlbeverage. The beverages were con-sumed immediately after exercise andagain 1 hour later. Measurements ofmuscle fiber size, maximal strength,

and body composition were under-taken both before and after 12 weeks oftraining. Although no between-groupdifferences were noted for changes instrength, type II muscle fiber area andlean body mass increased significantlymore in the milk group compared withthe soy and control groups. Type Imuscle fiber area increased after train-ing only for the milk and soy con-sumers, with the increase in themilk-consuming group being signifi-cantly greater than in the controlgroup. There was also a significantlygreater decrease in fat mass in the milkgroup compared with that in the soyand control groups.

KEY POINT

The long-term postexercise consump-tion of bovine milk (which is approx-imately 80% casein and 20% whey)promotes greater muscle hypertrophyduring the early stages of resistancetraining in novice weightlifters com-pared with isoenergetic soy or carbo-hydrate consumption (13).

PRACTICAL APPLICATIONS

Although it is not possible to makeconclusive recommendations regard-ing protein intake for optimal per-formance, the following observationsand recommendations are madeconsidering the current body ofliterature:

1. Athletes wishing to enhance leanmass from resistance exerciseshould never train fasted nor remainfasted in the immediate postexerciseperiod. Assuming total energy needsare being met, training-inducedgains in strength and lean masscan be significantly improved whenathletes are given proper pre- andpostexercise (i.e., periworkout)nutrient combinations.

2. With the exception of recent studieson chocolate, milk, and eggs, theeffects of whole foods and drinks onMPS and MPB have not beenstudied in humans. As a result, itshould be acknowledged by nutri-tionists and conditioning professio-nals that the common ‘‘food first’’recommendation, at least in the

periworkout period, is based almostentirely on speculation from studiesusing crystalline essential aminoacids and carbohydrates.

3. Because of the technical expertiseand cost involved in performingmetabolic tracer studies, samplesizes are small (often ,10 homoge-neous subjects), variances are large,and the generalizability of dose-response findings to many athletesis limited. Moreover, the resistanceexercise stimulus in most studies todate has used lower-body exerciseonly (with serial biopsies of only 1muscle), and the exercise volume issubstantially lower than what manyathletes actually do. For these rea-sons, it is our opinion that theoptimal protein and/or aminoacid–dosing regimen for elite ath-letes in the periworkout period isprobably higher than that recom-mended by the primary literature,particularly when greater volumesof exercise and/or whole bodytraining is performed.

4. Essential amino acids ingestedbefore resistance exercise lead toa greater increase in muscle proteinaccretion than when they areingested after exercise. In contrast,whole whey proteins ingestedbefore or after resistance exerciselead to similar effects on amino aciduptake, regardless of the timing ofingestion.

5. Although the optimal amount ofwhey protein and whole foodchoices that are necessary to max-imize muscle protein accretion hasnot been studied to date, a prudentrecommendation at this time forstrength/power athletes is to con-sume a postworkout nutrient mix-ture that contains approximately2 parts carbohydrates to 1 partprotein, where protein intake con-stitutes 0.25–0.50 grams per kilo-gram of body mass. For team sportathletes, a 3:1 ratio is recommended.For endurance athletes, a 4:1 ratio isrecommended. A similar macronu-trient combination should also beconsumed every 1–2 hours thereaf-ter for at least 6 hours after exercise

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(i.e., a total of 3–4 postexercise‘‘meals’’ should be consumed withinthe 6-hour postexercise window)to maximize adaptive responses inmuscle. If caloric intake is a concern,then essential amino acids can beused instead of whole protein, withan intake of 0.15–0.30 grams ofessential amino acids per kilogramof body mass. One scoop of high-quality whey protein containsapproximately 10–12 g essentialamino acids.

6. Of all the essential amino acids,leucine appears to be the mostimportant trigger controlling MPS.Although still somewhat specula-tive, leucine doses of approximately3–9 g (0.12 g leucine per kilogramof lean body mass) per meal appearnecessary to maximally stimulateMPS during the postexercise period.Because older muscle has beenshown to have defects in leucineand insulin signaling, even higheramounts of leucine, as well asadditional carbohydrates, may benecessary to maximize muscle pro-tein accretion in older athletes. Onescoop of high-quality whey proteincontains approximately 2–2.5 g ofleucine.

7. Coaches and athletes should beencouraged to speak with qualifiedsports nutritionists to help identifyunique nutritional strategies for op-timal performance.

Tim Ziegenfuss

is a certified sportsnutritionist andcurrently consultswith college-,Olympic-, andprofessional-level

athletes as the CEO of the Center forApplied Health Sciences in Fairlawn, Ohio.

Jamie Landis isa tenured professorof biology atLakeland Com-munity College in

Kirtland, Ohio, and founder and directorof the Lakeland Youth Sport ScienceInstitute, an athletic training/conditioninginstitute for children aged 6–15.

Robert A.

Lemieux is thehead strength andconditioning coachat Kent State

University and is completing requirementsfor a master’s degree in nutrition.

REFERENCES1. Cribb PJ and Hayes A. Effects of

supplement timing and resistance exercise

on skeletal muscle hypertrophy. Med Sci

Sports Exerc 38: 1918–1925, 2006.

2. Cribb PJ, Williams AD, Carey MF, and Hayes

A. The effect of whey isolate and resistance

training on strength, body composition, and

plasma glutamine. Int J Sport Nutr Exerc

Metab 16: 494–509, 2006.

3. Drummond MJ and Rasmussen BB.

Leucine-enriched nutrients and the

regulation of mammalian target of

rapamycin signalling and human muscle

skeletal muscle protein synthesis. Curr

Opin Clin Nutr Metab Care 11: 222–226,

2008.

4. Drummond MJ, Dreyer HC, Pennings B,

Fry CS, Dhanani S, Dillon EL, Sheffield-

Moore M, Volpi E, and Rasmussen BB.

Skeletal muscle protein anabolic response

to resistance exercise and essential amino

acids is delayed with aging. J Appl Physiol

104: 1452–1461, 2008.

5. Hartman JW, Tang JE, Wilkinson SB,

Tarnopolsky MA, Lawrence RL, Fullerton AV,

and Phillips SM. Consumption of fat-free

fluid milk after resistance exercise

promotes greater lean mass accretion than

does consumption of soy or carbohydrate

in young, novice, male weightlifters. Am J

Clin Nutr 86: 373–381, 2007.

6. Hulmi JJ, Kovanen V, Selanne H, Kraemer WJ,

Hakkinen K, Mero AA. Acute and long-term

effects of resistance exercise with or without

protein ingestion on muscle hypertrophy and

gene expression.Amino Acids 37: 297–308,

2009.

7. Koopman R, Pennings B, Zorenc AHG, and

van Loon LJC. Protein ingestion further

augments S6K1 phosphorylation in skeletal

muscle following resistance type exercise

in males. J Nutr 137: 1880–1886, 2007.

8. Moore DR, Robinson MJ, Fry JL, Tang JE,

Glover EI, Wilkinson SB, Prior T,

Tarnopolsky MA, and Phillips SM. Ingested

protein dose response of muscle and

albumin protein synthesis after resistance

exercise in young men. Am J Clin Nutr

89: 161–168, 2009.

9. Tang JE, Manolakos JJ, Kujbida GW,

Lysecki PJ, Moore DR, and Phillips SM.

Minimal whey protein with carbohydrate

stimulates muscle protein synthesis

following resistance exercise in trained

young men. Appl Physiol Nutr Metab

32: 1132–1138, 2007.

10. Tang JE and Phillips SM. Maximizing

muscle protein anabolism: The role of

protein quality. Curr Opin Clin Nutr Metab

Care 12: 66–71, 2009.

11. Tipton KD, Elliott TA, Cree MG, Aarsland

AA, Sanford AP, and Wolfe RR. Stimulation

of net muscle protein synthesis by whey

protein ingestion before and after exercise.

Am J Physiol Endocrinol Metab 292: 71–76,

2007.

12. Tipton KD and Ferrando AA. Improving

muscle mass: Response of muscle

metabolism to exercise, nutrition and

anabolic agents [review]. Essays Biochem

44: 85–98, 2008.

13. Wilkinson SB, Tarnopolsky MA,

Macdonald MJ, Macdonald JR, Armstrong

D, and Phillips SM. Consumption of fluid

milk promotes greater muscle protein

accretion after resistance exercise than

does consumption of an isonitrogenous

and isoenergetic soy-protein beverage.

Am J Clin Nutr 85: 1031–1040, 2007.

14. Willoughby DS, Stout JR, and Wilborn CD.

Effects of resistance training and protein

plus amino acid supplementation on

muscle anabolism, mass, and strength.

Amino Acids 32: 467–477, 2006.

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